Browsing by master's degree program "Magisterprogrammet i botanik"
Now showing items 1-20 of 23
-
(2024)Plants have evolved mechanisms to cope with various environmental stresses, including abiotic factors like temperature extremes and biotic factors involving the interactions with pathogens and herbivores. Kale (Brassica oleracea var. acephala) is a superfood famous for containing many compounds that are beneficial in the human diet but are primarily produced as specialised metabolites to aid in plant defence. Amongst these are glucosinolates which are defence compounds characteristic of plants in the Brassicaceae family. The aim of this study was to investigate how the diverse metabolic profiles of kale cultivars contribute to postharvest resistance against herbivory and necrotrophy. To assess the resistance of each kale cultivar against herbivory, I used the larvae of the wood tiger moth Arctia plantaginis as a test subject. We used detached leaves from 30 kale cultivars in an overnight feeding experiment with the larvae. The same 30 cultivars were used in a postharvest infection experiment with a generalist necrotroph B. cinerea to investigate the resistance of each kale cultivar against necrotrophy. For a comparative experiment between necrotrophs, we selected 10 kale cultivars to assess the necrosis caused by B. cinerea and a specialist necrotroph A. brassicicola. The A. brassicicola-infected and mock-treated leaves were analysed for their metabolic profiles to observe how these were altered by the infection. The weight gain of the tiger moth larvae was not significantly affected by the kale cultivars or their sugar content. A correlation between sucrose and indole glucosinolates might have reduced the kales’ palatability and potentially deterred the herbivores. In the B. cinerea experiment, we observed a positive correlation between necrotic lesion area and protein, sucrose, and indole GSL contents in kale leaves, even though indole GSLs are generally considered defence molecules against necrotrophic pathogens. When comparing the necrotic damage caused by the two necrotrophs, the specialist A. brassicicola exhibited a statistically significantly more violent infection compared to B. cinerea. Chlorophyll became degraded in the infected leaves compared to the uninfected controls. Amino acid content was high in the aged control and infected leaves, indicating protein degradation either due to senescence or cell wall-degrading enzymes from the pathogen. There was a statistically significant positive correlation between necrotic damage and protein in the infected leaves potentially due to proteins being secreted by the pathogen during infection. Starch levels decreased in the infected leaves compared to the controls. The infected samples also showed decreased glucose amounts potentially being taken up by the necrotroph during infection. Altogether, the study showed that kale cultivars respond to biotic stress factors by triggering metabolic changes that can affect the disease resistance and postharvest quality of the leafy vegetables.
-
(2024)Drought events will increase in the future due to climate change and thereby threaten agricultural production. The growing world population needs stable yields nonetheless thus, solutions need to be found. One way to do so is to explore mechanisms that allow plants to withstand harsh conditions and recover from them. Autophagy is such a mechanism. It is a bulk degradation pathwaythat allows plants to recycle cell components. During biotic and abiotic stress autophagy pathways are enhanced. Even though this mechanism is very useful and is proven to enhance abiotic stress tolerance, very little is known about it in plants. This thesis aimed at defining the informative time points for drought and autophagy response during drought and recovery in barley. To do so barley plants were subjected to gradual drought by withholding irrigation. They were kept at a level of severe drought for 4 days and were then rewatered. The tip of the third leaf was sampled for RNA extraction followed by qPCR. The genes this thesis focused on were GST and HSP17 as indicators of drought stress and ATG6 as indicator for autophagy. Additionally, phenotypic data was collected via RGB imaging for monitoring wilting and thermal imaging for stomata closure. GST was upregulated during the onset of drought, which seems to make it an early response gene, while HSP17 was upregulated during severe drought. ATG6 had a high transcription rate during all stages of drought and only decreased during recovery. However, because the primer efficiencies calculated in this experiment appear to be very low, and data points were missing due to pipetting practice, the results are not reliable and need to be repeated. Thus, no prediction about the informative time points can be made. The thermal data showed good results and the expected pattern of stomatal closing during drought could be observed. But because the greenhouse is a variable environment a reference would make the data even more precise.
-
(2022)Woodland strawberry (Fragaria vesca) is a perennial herb in the Rosaceae family with dimorphic leaves, summer and winter leaves, adapted to seasonal climate. Woodland strawberry produces a new set of leaves in spring that are photosynthetically active throughout the summer season (summer leaves), and the leaves senescence in autumn when they are replaced by a new set of leaves (winter leaves). The winter leaves retain photosynthetic capacity under the snow cover throughout the winter season, which prolong the photosynthetic period of the species. With the world-wide climate warming, the thickness of winter snow is decreasing, which can affect overwintering and spring phenology of plants. This thesis focuses on springtime ecophysiology and phenology of the senescing winter leaves and the formation of new summer leaves of woodland strawberry genotypes of different European origin. The 15 different genotypes of woodland strawberry are from Iceland, Italy and Norway, and they originate from different environments that are geographically separated from each other, so the populations are genetically distinct. In this study, these genotypes were kept at two different overwintering sites, coastal site at the Åland islands with mild temperatures, and continental site in Lammi with a persistent snow cover. According to the results all 15 genotypes showed earlier development of the summer leaves and earlier senescence of winter leaves in the group with Åland as overwintering site than in the group with Lammi. Another important finding is that the first summer leaves produced in spring begun to senesce shortly after they are fully developed and were replaced by later formed summer leaves. Specifically, the dates of summer leaf formation, flowering and stolon production were advanced, and the dates of winter leaf senescence were also advanced. The value of different leaf types to chlorophyll fluorescence was also lower at the Åland site. Therefore, it can be concluded that overwintering conditions have an effect on the subsequent phenological development in spring. In the context of global climate change, the spring development of woodland strawberry will be earlier, and the senescence of winter leaves will also be earlier.
-
(2024)Secondary growth in plant vasculature tissues originate from meristematic tissue vascular cambium. Vascular cambium produces xylem inwards and phloem outwards in the plant root and stem. Vascular cambium regulatory mechanisms are not completely known, and while plants and especially trees are dependent on the mechanical support and transportation systems the vasculature provide, increased knowledge of the vascular cambium and especially xylem development is valuable. In this thesis, I explored Arabidopsis thaliana single-cell RNA-sequencing data from secondary growth stage via cloning transcriptional reporter lines, and later utilized the transcriptomics data to find potential xylem development regulators. By loss-of-function mutant and inducible overexpression line screening, I found two genes in a family of MYB transcription factors to be potential regulators in xylem development. Loss-of-function mutant did not show significant phenotype, but overexpression lines under constitutive 35S promoter showed extreme halt of growth, and a stain-filled vessel phenotype in a fixed and resin-embedded Arabidopsis cross-section. Under developing xylem -specific promoters, inducible overexpression lines showed the same phenotype, and while grown to the secondary growth stage, I detected some patterning defects. Thus, these results indicate, that these MYBs expressed in the xylem parenchyma in the single-cell transcriptomics data, might have a function in xylem development.
-
(2020)Leaf senescence is a developmental and physiological phase in plants to end leaf development. Environment factors such as drought stress, extreme temperature, and pathogen threat and internal factors including age and reactive oxygen species induce leaf senescence. Some phytohormones such as jasmonic acid and salicylic acid play a key function in cell death in plants. WRKY transcription factors is known as one of the largest transcription factor family in plants which regulates a variety of plants processes. WRKY75 which belong to WRKY transcription factors has shown multiple functions in plant development like regulation of Pi starvation responses and root development and flowering. In my thesis, I focused on the role of WRKY75 in senescence and stress responses. WRKY75 was identified as a positive regulator of cell death in Arabidopsis. WRKY75 can promote salicylic acid biosynthesis by promote transcript levels of SID2 and also cause hydrogen peroxide accumulation by suppressing the transcription of CAT2. Hydrogen peroxide and salicylic acid can promote WRKY75 transcription at the same time. To evaluate the function of WRKY75 transcription factor in SA signalling and cell death, three lesion mimic mutants acd5, cat2, dnd1 and their corresponding wrky75 double mutant were used. Interestingly, no different phenotypes were found between acd5, cat2, dnd1 and their corresponding wrky75 double mutants in cell death and hydrogen peroxide accumulation detection in Arabidopsis leaves. Meanwhile, marker genes transcription levels were not different in both short day and long day growth condition. However, different phenotypes were observed in botrytis infection. Based on these results, we formed a hypothesis that gene redundancy could influence genetic characterization of WRKY75. To overcome this problem, SRDX-WRKY75 chimeric repressor transgenic lines were generated. The SRDX domain act as a dominant negative regulator to suppress WRKY75 target genes. In future research, these new lines can be used to test transcript levels for putative WRKY75 target genes.
-
Initiation of lignification in Norway spruce xylem detected by immunolabeling and Raman spectroscopy (2021)Wood development is a significant process with both financial as well as natural perspectives. Trees and wood are of highly significance in Finland where a huge part of the gross national income devises from the forestry area. Ecologically and commercially the Norway spruce (Picea abies) is one of the most common tree species in Europe. It covers about 30% of Finland's forest area. Norway spruce is frequently used in research to study many phenomena related specifically to the wood formation and lignification. The principal objective of my thesis work was to reveal an unknown step in the lignification process in developing xylem of Norway spruce, i.e. the initiation site(s) for lignification. To achieve this goal, the aim was to investigate the chemical identity of possible lignification initiation sites in the middle lamellae and cell corners of developing Norway spruce xylem, and to answer the question where in the cell wall soluble monolignols first emerge and lead to the start of lignin formation (polymerization). I was approaching this goal with immunolabeling technique for confocal microscopy and Raman spectroscopy to unravel this initiation site of lignification by using specific monoclonal antibodies for cell wall compounds and comparing the results with the initial lignin deposition sites. To detect the location/distribution of some important polysaccharides and lignin substructure for lignification initiation, monoclonal antibodies i.e. LM10, LM11, LM15, LM24 and antibody Dibenzodioxocin or DBD were applied for confocal microscopy and some monolignol specific spectra were applied for Raman microscopy. The xylan was detected by LM10 in secondary cell wall abundantly and few are in primary cell wall of Norway spruce. The LM11 against arabinoxylan was determined more in primary cell walls but less in secondary cell wall. The location of xyloglucan was identified in the middle lamellae, primary and secondary cell wall of Norway spruce by LM15. The LM24 against glycosylated xyloglucan was found in secondary cell walls, abundantly in cell corners but few in primary cell wall. The primary antibody Dibenzodioxocin or DBD for the lignin substructure revealed that these were present in the mature cells of secondary cell walls (S2 and S3 layers). The lignin substructures DBD were not found in youngest cells where secondary cell walls are absent. The developing xylem of Norway spruce was subjected Raman microscopy and which revealed the locations of cinnamyl alcohol, coniferyl alcohol and coniferyl aldehyde. The cinnamyl alcohol was abundantly found at cell corner and middle lamellae in most developing part of xylem. The coniferyl alcohol was determined only in developing xylem cell corners. The coniferyl aldehyde was observed at cell corners, middle lamella and primary cell walls of developing xylem. The coniferyl aldehyde was located more in mature cells than younger cells. So, the Confocal and Raman microscopy images revealed the possible bindings of monolignols to polysaccharide in young cell corners, cell wall layers and middle lamellae.
-
(2023)Climate change is applying pressures to plant populations, which must adapt or move to retain fitness. A changing climate highlights the need for us to understand the potential that species possess to evolve in addition to any plastic responses. Approaches that allow the study of contemporary evolution, such as resurrection studies, have the capacity to provide insights into the responses of populations to these changes. In this resurrection experiment, seeds from seven populations of Hypericum perforatum collected from the UK and France, and their historic counterparts, were grown and subjected to four temperature treatments. Three traits were measured and compared between historic and contemporary populations: date of flowering, average seed weight and flower abundance. I found that temperature influenced date of flowering and flower abundance, leading to an overall earlier flowering time and an overall decrease in flower abundance with increase in temperature. The only significant difference between historic and contemporary populations was found in flower abundance - where, whilst flower abundance declined with increasing temperature, contemporary populations produced proportionally more flowers than historic populations per degree of temperature increase. These results suggest that plasticity allows this species to adjust its flowering phenology to retain fitness in warmer conditions but that evolution during the past decades may have selected for a decreased flower abundance at higher temperatures. These findings contribute to our overall understanding of how species have and will react under climate change, as we try to disentangle the roles that plasticity and evolution play in enabling populations to retain fitness under changing conditions.
-
(2021)Kurtturuusu (Rosa rugosa) on haitallinen vieraslaji Suomessa. Se on levinnyt alkuperäisiltä esiintymisalueiltaan Koillis-Aasiasta Itämeren ja Pohjanmeren rannikolle sekä Pohjois-Amerikan koillisosiin. Se uhkaa luonnon monimuotoisuutta erityisesti merenrannoilla. Suomessa kaikki hiekkarantojen ja dyynien luontotyypit ovat uhanalaisia ja kurtturuusu vaikuttaa erityisesti niiden ekosysteemeihin muodostamalla suuria tiheitä kasvustoja. Kurtturuusukasvustossa muut lajit vähenevät. Vieraslajilain nojalla kurtturuusun kasvattaminen on kielletty, mutta kasvatuskielto astuu voimaan vasta siirtymäajan jälkeen 1.6.2022. Kurtturuusu on suosittu koristepensas. Siitä on myös jalostettu uusia lajikkeita. Niiden kasvatusta kielto ei koske, koska niiden lisääntymiskyvyn on ajateltu olevan heikko. Tutkimuksen tavoitteena oli selvittää kurtturuusun levinneisyyttä Espoon rannoilla sekä tutkia sen lisääntymiskykyä. Tutkimuksessa kartoitettiin Espoon merenrantoja järjestelmällisesti maastossa havainnoiden ja etsittiin niiltä kurtturuusua. Kasvustojen ominaisuuksia tutkittiin ja selvitettiin morfologisten tuntomerkkien avulla, ovatko ne kurtturuusun perusmuotoa vai jotakin jalostettua lajiketta. Kasvustoista valittiin osa tarkempaa siementutkimusta varten. Siementen elinkykyä tutkittiin tetrazoliumtestin avulla ja kelluntakykyä vesiastioissa. Siementutkimuksessa selvitettiin, eroaako kurtturuusun perusmuodon ja jalostettujen lajikkeiden siementuotto tai siementen elinkyky toisistaan ja kuinka hyvin pähkylät kelluvat. Tilastollisina menetelminä käytettiin varianssianalyysiä ja t-testiä. Kurtturuusua kasvoi Espoon rannoilla runsaasti monenlaisilla kasvupaikoilla sekä istutettuna että villiytyneenä. Mantereella sitä oli enemmän kuin saaristossa. Villiytyneenä tai mahdollisesti villiytyneenä kasvoi vain muutamia kasvustoja jalostettuja kurtturuusulajikkeita. Istutettuina niitä oli enemmän. Kurtturuusun siementuotto vaikuttaa olevan suurempi perusmuodolla kuin jalostetuilla lajikkeilla. Perusmuoto tuotti myös keskimäärin enemmän elinkykyisiä siemeniä. Hajonta molemmissa ryhmissä oli kuitenkin suurta. Osa jalostetuista lajikkeita tuotti melko runsaastikin elinkykyisiä siemeniä, toiset taas hyvin vähän. Kurtturuusun pähkylät kelluivat hyvin. Tulokset tukevat käsitystä siitä, että jalostetut kurtturuusulajikkeet eivät olisi yhtä haitallisia kuin perusmuoto. Sekä perusmuodon että jalostettujen lajikkeiden siementuoton ja elinkyvyn hajonta oli kuitenkin suurta. Eri lajikkeiden eroja olisikin tarpeen selvittää järjestelmällisesti. Kurtturuusulla on hyvät edellytykset levitä veden välityksellä uusille kasvupaikoille, koska se kasvaa rannoilla ja sen siementen kelluntakyky on hyvä. Kurtturuusun kartoitus Espoossa auttaa sen torjunnan suunnittelussa myös muissa kaupungeissa.
-
(2022)Maisterintutkielman tarkoituksena oli selvittää, mitä talvivihreitä puutarhakasveja Suomessa kasvaa puutarhoissa, ovatko talvivihreät puutarhakasvit ihmisille tärkeitä ja minkälaisia talvivaurioita ihmiset ovat talvivihreillä kasveillaan havainneet. Ilmastonmuutos muuttaa talvet Suomessa vähälumisemmiksi ja pimeämmiksi, ja talvi voi siten tuntua harmaammalta. Talvivihreiden kasvien merkitys ihmisille voi korostua tulevaisuudessa, sillä talvivihreys lisää kasvin koristearvoa ja on erityisen tärkeää pimeänä ja harmaana talvikautena, kun muissa kasveissa ei ole lehtiä. Ilmastonmuutoksen myötä myös talvivihreillä kasveilla havaituissa talvivaurioissa voi tapahtua muutoksia. Tutkimuksen aineisto kerättiin internetissä olleella kyselytutkimuksella. Tietoa kyselystä jaettiin sosiaalisessa mediassa. Kysely kohdennettiin puutarhasta kiinnostuneille ihmisille, ja kysely oli avoinna vastauksille noin kolme viikkoa loka - marraskuussa 2021. Kyselyyn saatiin 154 vastausta eri puolilta Suomea. Vastaukset jaettiin puutarhakasvien kasvuvyöhykkeiden mukaan ja eri kasvuvyöhykkeiden tuloksia verrattiin keskenään. Kyselytutkimuksen tuloksista selvisi, että talvivihreät puutarhakasvit ovat ihmisille tärkeitä, ja erityisesti vähälumisilla alueilla talvivihreät kasvit koetaan todella tärkeiksi. Talvivihreiden kasvien lajimäärä oli tutkimuksessa kaikilla alueilla lähes sama, ja kaikilla alueilla ilmitalvehtijoiden lajimäärä oli suurin muihin kasvien elomuotoihin verrattuna. Tutkimuksen mukaan suosituimpia talvivihreitä puutarhakasveja ovat tuijat, alppiruusut ja maksaruohot. Kaikista talvivaurioista eniten on havaittu lehtien osittaista ruskettumista ja lumen painon aiheuttamia vaurioita. Eniten talvivaurioita on havaittu juuri tuijilla ja alppiruusuilla, joten havaittujen vaurioiden suuri määrä voi liittyä lajien yleisyyteen. Tutkimuksen mukaan kuitenkaan lumen määrä ei vaikuttanut talvivihreillä kasveilla havaittujen talvivaurioiden määrään.
-
(2022)Gravity has a modifying effect on plant architecture. The phytohormone auxin is known to transmit the signal of gravity perception from gravity-sensing cells to responsive tissues and cause an asymmetric growth response in the receiving organs. Intercellular auxin flux is mediated by many different transporter proteins, of which PIN-FORMED 3 (PIN3) is known to function as an auxin efflux carrier in gravitropic responses. The expression of PIN3 is known to locate in one cell layer of the shoot endodermis in herbaceous plant species and Populus hybrids. The objective of this study was to determine the location of PIN3 ortholog expression using silver birch (Betula pendula) as a model plant of a woody plant species. Agrobacterium tumefaciens C58 strain GV3101 (pMP90), harbouring binary vector pBpPIN3-erVEN-nosT2 containing erVenus (erVEN-YFP) as a marker gene under the BpPIN3 promoter and terminator nosT2, was used in the study to detect the gene expression. The expression vector was constructed by the Gateway® cloning method and transformed into in vitro shoot explants of silver birch by Agrobacterium-mediated transformation (AMT). In the study, transgenic lines were generated successfully, from which the fluorescence of erVEN was observed in the cross-section of the shoot with a fluorescence stereo microscope. The transgenicity of putative transgenic lines was confirmed by PCR of erVEN. BpPIN3 was likely to be expressed to endodermal tissue in the shoots of silver birch. This study can be considered as a screening step for the localization of BpPIN3 expression. The study facilitates the discovery of factors related to the regulation of PIN3 in tropic responses in woody plant species. This information can in the future be utilized in plant breeding to optimize plant architecture.
-
(2022)Environmental factors are important tools in constructing methane flux models and estimations. Among the abiotic factors, plants and their functional groups have been noted to have significant effect on methane fluxes for three reasons. First, the vegetation community compositions express their abiotic environmental factors that affect not only the plants, but also local methanogen and methanotroph communities. Second, the vegetation itself might produce methane emissions and have a direct effect on methane balance. Third, the plant functional groups and species have differences in their chemical and physical properties that support different methanogen communities and therefore have an indirect impact on methane fluxes. In this study, methane fluxes of different plant communities were observed during one growing season in northern boreal catchment area in Muonio. Study focuses to determine the link between methane fluxes and abiotic and biotic environmental factors in different vegetation types. Closed chamber technique was used to measure methane and carbon dioxide fluxes from 23 plots every two weeks in period of June-August. Environmental data, such as moisture, temperature species composition etc. were collected from the plots. Vegetation types for each plot were determined via ordination analysis. Linear mixed-effects regression model and generalized additive model were applied and compared to observe the relationships of methane and environmental factors in different vegetation types. Dataset was divided into four vegetation types in clustering analysis: wet fen, pine bog, spruce swamp and forest. The greatest amount (average 5959 µg/m²/h) and biggest range (standard deviation 5285 µg/m²/h) of methane emissions were observed on wettest fen-like study sites. Peatland types in general acted as net methane sources. The driest, forest-like vegetation type acted as a net methane sink. The amount (average -107 µg/m²/h) and range (standard deviation 117 µg/m²/h) of methane fluxes were very moderate in comparison to peatland types. These effects intensified towards the climax of growing season. The most significant environmental factors were mostly abiotic on driest study sites and the whole plant biomass was more significant biotic methane flux regulating factor than plant functional groups. On wetter study sites, the role of abiotic factors decreased, and plant functional group increased. Graminoids were linked to bigger methane emissions especially on wetter study sites. Forest mosses and different shrub types seemed to have a link with lower methane emissions or methane absorption. The effect of other plant functional groups on methane fluxes varied more, and their role remains unclear. None of the environmental factors could estimate the methane flux alone, and the methane budget seems to be a sum of multiple variables in each vegetation type. The role of plant functional groups varied in different vegetation types and was dependent on surrounding vegetation. More research is needed to get better tools to estimate methane balance and to understand the underlying mechanisms in climate and environmental change.
-
(2024)As biodiversity is declining globally, there is a crucial need to understand the connections between diversity and ecosystem functioning. Research has shown that diversity tends to lead to higher productivity, but our understanding of the underlying reasons is still limited. For example, biotic interactions with mycorrhizal fungi could cause these diversity effects in plant communities, but few studies have assessed the subject. In this thesis, I studied the impacts of arbuscular mycorrhizal symbiosis on diversity effects with three research questions. First of all, I aimed to determine whether mycorrhizal symbiosis affects the diversity–productivity relationship across plant communities. Secondly, I divided diversity effects into two parts: complementarity and selection effects. These effects can be determined statistically. Finally, I studied how different species within the community respond to diversity. To answer these questions, I conducted a greenhouse study with varying plant communities. I manipulated the plant species diversity and used a fungicide treatment to suppress mycorrhizal fungi. After the growing period, I measured the biomasses of the plants as an indicator of productivity. I tested the effectiveness and side effects of the fungicide by estimating mycorrhizal colonization rates in plant roots and by testing its effects on non-mycorrhizal plant species. The fungicide treatment did not affect diversity–productivity relationship nor diversity effects significantly. However, fungicide treatment failed to reduce the overall mycorrhizal colonization rate and had varying effects on different plant species. One of the plant species benefitted from species diversity whereas other species experienced either no effect or a negative effect of increased diversity. No specific trait explained the varying responses on diversity. More research is needed to understand plants’ complex responses to decreasing biodiversity and biotic interactions, as well as to clarify whether fungicide is a fitting method for mycorrhizal suppression studies.
-
(2024)Nuclei isolation is a method used e.g. as a part of chromatin structure research. DNA structure can be examined in its 3D form from isolated nuclei because DNA is still wrapped around the histone proteins. Examining the chromatin structure can offer information e.g. about gene expression and how it is regulated. Isolating nuclei from plant cells demand more optimization compared to animal cells because of the cell wall, chloroplasts and secondary metabolites. The presence of organellar DNA can hamper the later DNA analysis. Secondary metabolites can hinder the actual isolation process. Finding the suitable isolation protocol for species of interest may need careful optimization of different aspects. Different species can differ from each other based on the structural and biochemical characteristics and because of this the same protocol may not ensure as good results for them. Different tissue types of the same species may have also differences in their biochemical and structural characteristics. In this thesis work, three different isolation protocols were used for three plant species; Pinus sylvestris, Betula pendula and Arabidopsis thaliana. The purpose of the work was to compare the results from each nuclei isolation protocol. Optimization of isolation protocol for P. sylvestris and B. pendula would help the isolation process for later research. Thesis work was done to get guidance for this optimization. Samples handled with different protocols were different from each other based on the sample concentration (particles/mL) and the average size of isolated particles. Chloroplast contamination was tested with chloroplast specific primers with PCR. None of the samples were free from chloroplasts.
-
(2023)The above-ground surfaces of plants (the phyllosphere) are inhabited by a diverse variety of microbes that interact with the host plant affecting its health and growth. One of the predominant factors influencing the composition and formation of the phyllosphere microbial community is the species and genotype of the plant. In my thesis, I investigated whether three different Rubus species (R. arcticus, R. saxatilis, and R. chamaemorus) form similar phyllosphere microbial communities, and whether the genotype of the host plant has more impact on the community composition than the microbiota that the plants are exposed to. I also tested how different microbiota treatments would affect Rubus plant growth. The experiment was conducted with micropropagated plants of the three aforementioned Rubus species. The plants were treated with different microbiota collected from the leaves of wild plants of the three Rubus species and the growth of the plants was observed. The phyllosphere fungal and bacterial communities of the plants were sequenced from leaf samples and analyzed to inspect the overall diversity and difference of the communities (using Kruskal-Wallis test and PERMANOVA) and to identify possible core microbes within the Rubus species’ phyllosphere communities. I found that Rubus phyllosphere microbiota was dominated by bacteria classes Alphaproteobacteria and Gammaproteobacteria, and fungal classes Eurotiomycetes, Sordariomycetes, Agaricomycetes, and Dothideomycetes. The host plant genotype had more significance on the composition of phyllosphere microbiota than the origin of the microbiota. The different microbiota treatments had no significant effect on the plant leaf growth. My thesis shows how host plant genotype influences the shaping of the phyllosphere communities as well as how transferable the microbial communities are between species from the same genus. Understanding of the phyllosphere microbiota can have potential applications in the promotion of plant health and fitness.
-
Plant biodiversity and ecosystem functioning in a latitudinal gradient of heath forests in Finland (2024)In this thesis, I study plant biodiversity and ecosystem functioning in Finnish heath forests. To improve the understanding of how terrestrial understory plant biodiversity affects forest ecosystem functioning, I use structural equation modelling with information from climate and landscape land cover, using study areas along a 800 km latitudinal gradient. In addition, I describe the characteristics of the studied plant communities from taxonomical and functional point of view together with related environmental variables. I conducted a field survey during summer 2022. Study area consisted of five regions, ranging from southern Finland to near Arctic Circle: Tvärminne, Helsinki Metropolitan Area, Evo, Konnevesi and Kuusamo. I sampled and identified terrestrial vascular plants, lichens and bryophytes by coverage from 80 vegetation plots of 1 m2 in each region. In total, data consists of 400 vegetation plots and total amount of species was 134. We measured environmental variables in the field or draw them from remote sensing databases. To model the causal pathways among climate, landscape land cover, forest ecosystem functioning measured as Normalized Difference Vegetation Index (NDVI) and terrestrial understory plant biodiversity, I constructed six structural equation models (SEM) with different combinations of taxonomical biodiversity metrics and landscape land cover variables. Based on previous studies I hypothesized that biodiversity is positively related to ecosystem functioning. Models explained 17 – 21 % of observed variation in ecosystem functioning. The most important explanatory variable was the number of growing degree days and the second most was the taxonomical understory biodiversity. To provide functional summary of the studied plant communities, I categorized plant species according to their functional group as well as Grime’s CSR Triangle Theory’s strategy classes. The three strategy classes places species according to their high or low tolerance to stress and disturbance. Three classes are competitors (C), stress-tolerators (S) and ruderals (R). S-strategy was most common in all areas but variation between regions was observed. This emphasizes the importance of functional and compositional dimensions of biodiversity in addition to taxonomical biodiversity since loss or shift in them can lead to lost or altered ecosystem functioning. There is now a broad scientific consensus that biodiversity influences ecosystem functioning and thus the ongoing biodiversity loss is an existential threat to humanity as we depend on functioning ecosystems and their ability to produce ecosystem services. This study is important since it provides indicative empirical evidence from complex real-world ecosystems that has been limited as most biodiversity-ecosystem functioning (BEF) -studies have been experimental. Biodiversity information data also creates benchmarks for future comparison and latitudinal gradients describe how biodiversity varies across space.
-
(2024)The many symbiotic microbes associated with plants can represent the first line of defence against viral pathogens, which can have profound impacts on plant health and productivity. Unfortunately, although countless studies have investigated variations in the composition of microbial communities associated with crops, showing benefits in the plants’ nutrient acquisition, stress tolerance or growth promotion, much less is known about how viruses might affect the composition of the microbiota associated with plants, and especially non-crop plants. Furthermore, we also often lack an understanding of how plant viruses are transmitted across their environment. Addressing these knowledge gaps is bringing us closer to better describe and manage the complex relationships between plant microbiota and viral pathogens in their natural environment. The main objective of my Master’s study is to examine variations in the bacterial community associated with a plant in the agricultural landscape, and to identify potential players in microbial community changes. With this in mind, I chose to work with the ribwort plantain, Plantago lanceolata, because it has a widespread distribution, it is present around cultivars, and there is extensive knowledge of its biology and genetics. Thus, P. lanceolata, represents an excellent system for investigating the causes of variation in the plant-associated microbiota. More precisely, I worked with the P. lanceolata population evolving in the Åland Islands, in Southwestern Finland, which has been the target of long-term ecological and evolutionary metapopulation studies. The population is also known for co-evolving with several viral pathogens, and with diverse Hemiptera insects (plant sucking-insects) that have been suggested as possible vectors of the viruses between plants. I collected P. lanceolata leaves, and insects found on P. lanceolata specimens from 28 habitat patches, or meadows, from five localities across the Åland Islands (Geta, Sund, Lemland, Finström, Eckerö). I extracted DNA from a total of 10 leaves per patch, as well as 60 Hemiptera specimens (of several uncharacterized species). I screened for viral infection in all samples by amplifying the viral loci for reverse transcriptase form Plantago latent caulimovirus (cauV) and the replication associated protein gene from Plantago lanceolata latent virus (PlLV). In parallel, I characterized the bacterial communities associated with each plant and insect through metabarcoding of the highly variable V5-V6 region of the 16S rRNA bacterial gene. My MSc's project shows that bacterial species richness (alpha-diversity metric) and community composition (beta-diversity metric) vary between plant and insects. But that they do not vary between the virus-infected and uninfected plants tested, and neither between geographical locations within the Åland Islands. This is the first study investigating the effects of two virus infections on the microbiota of a common weed from the Åland Islands. It provides preliminary data for the study of how the bacterial microbiota of P. lanceolata might respond to virus infections, and how viruses might be transmitted between individual plants.
-
(2024)Gerbera hybrida, a common ornamental plant, has natural resistance to fungal diseases. While there may be several bioactive compounds behind this trait, this master’s thesis focuses on two of them: gerberin and parasorboside. The gerberin/parasorboside biosynthesis has been profoundly investigated by Gerbera Laboratory at University of Helsinki. Gerberin and parasorboside are polyketide derivatives, a vast group of bioactive metabolites. The pathway that produces these compounds involves several enzymes: a polyketide synthase (PKS), two polyketide reductases (PKRs) and a glycosyl transferase. For gerberin to be synthesized, it requires presence of three enzymes: (1) G2PS1 (Gerbera 2-pyrone synthase 1) which initiates the chain by synthesizing the carbon backbone, and (2) an unknown first acting reductase, that continues the chain by reduction, lactonization, and (3) addition of a sugar molecule. Parasorboside production requires also a fourth enzyme, a reductase described by Zhu et al. (2022). This master’s thesis delves into post-modification of gerberin and parasorboside intermediates by the PKRs, which have not yet been verified. Until now, there has only been PKR-candidates for this position, derived from gerbera transcriptome library. The genes behind the proposed reductases were known from previous research. The objective of this master’s thesis is to demonstrate which of the proposed reductases coexpressed along with the G2PS1-reductase will produce the desired compounds (gerberin and parasorboside) in a model plant tobacco (Nicotiana tabacum in stable transformation and Nicotiana benthamiana in transient expression). The gene combinations were constructed into plasmids via PCR and Golden Gate cloning. Enzyme production was analysed by western blot and the secondary metabolites by HPLC. The hypothesis for this work was to produce the aglycones of gerbera’s natural products gerberin and parasorboside in the model plant tobacco via constructing the plasmids carrying our genes of interest. This master's thesis documents the successful construction of double and triple fusion plasmids, their integration into agrobacteria, and subsequent transformation into stably transgenic tobacco. Gerberin production in tobacco was observed with certain gene combinations, parasorboside production was not analysed yet in this work. Through meticulous work, the desired combination of genes for gerberin synthesis was identified in both agroinfiltrated plants with co-expressed genes and stable transgenic tobacco lines expressing genes from a single transcript cleaved by 2A-peptides.
-
(2024)Lichens are symbioses between fungi, photosynthetic algae and other organisms. The fact that several different fungi may occur in the same lichen thallus adds a further dimension to the diversity of these miniature ecosystems. Calicioids are a polyphyletic group of predominantly lichenised fungi which includes many species with stalked ascomata, topped with a persistent spore mass (mazaedium). One such species is Chaenotheca chrysocephala, a relatively common crustose lichen with a wide distribution. The lichenicolous fungus Chaenothecopsis consociata grows on the thallus of C. chrysocephala and is generally considered to be a parasite. This study aims to map the temporal and geographical distribution of C. chrysocephala and C. consociata in Europe in order to find out whether the parasite was present there before the year 1942, when the species was described, and to identify possible patterns which may affect the population dynamics of these two species. This study found that C. consociata was indeed present in Europe before 1942, at least in Norway, Sweden and Finland. Additionally, the percentage of infected C. chrysocephala thalli seems to have increased in Europe since the parasite was first found. The GBIF dataset showed a significant increase in infected C. chrysocephala thalli in northern Europe (N-EU) compared to central-southern Europe (CS-EU). Although the exact reason is unclear, this increase may be related to differences in forest structure across Europe. Firstly, the host lichen seems to prefer Picea and Pinus as its substrate, these being typical trees of needleleaf forests in Europe. Furthermore, the decrease of old-growth forest stands in Sweden and Finland may have reduced suitable habitat for the host, while the concurrent increase of disturbed stands may have favoured the dispersal of the parasite.
-
(2021)Improving land management to mitigate climate change is important, especially in agriculture on soils with high organic content. Many studies have found evidence that increasing diversity can help to improve plant biomass production and soil carbon storage. This is attributed to complementarity which consists of more efficient resource use due to niche differences and facilitative interactions. For the total climate impact, the effect of greenhouse gas emissions from the soil needs to be considered. To find out if adding more species to a grass mixture could have similar benefits in boreal zone grass cultivation in Finland, an experiment was set up with four different species mixtures, and three levels of species richness were established under a nurse crop. It was additionally of interest if these effects can counter the emissions of cultivation on organic soils. Biomass samples were collected both before the nurse crop was removed and at the end of the growing season. Both species richness and Shannon diversity index were considered as explanatory factors. Carbon exchange, divided into respiration and photosynthetic capacity, as well as nitrous oxide and methane fluxes, were monitored monthly. There was no strong evidence that species richness affects biomass or greenhouse gas fluxes during the first year. The effect of species richness on the biomass was clearer when the diversity index was considered. These results were significant when the lowest biomass values were excluded from the analysis, probably because complementary resource use needs enough biomass to have an effect. The differences in carbon flux measurements may be sensitive to timing within the growing season since the results closest to significant were obtained at the start of the season. At the time, the measurement conditions were good and the nurse crop biomass was small enough not to obscure the effects of grass mixture. When it comes to other greenhouse gases, species richness had most impact on early nitrous oxide emissions, while methane flux probably needs significantly more time for any changes to appear. Overall, the effect of species richness needs to be studied over the full grass cultivation cycle to find out the full effect. Based on current results, increasing species richness may be an option when other methods cannot be used to reduce emissions and improve carbon sink of agriculture.
Now showing items 1-20 of 23