Browsing by master's degree program "Master's Programme in Integrative Plant Sciences"

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.