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Browsing by Subject "auxin"

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  • Localization of PIN3 expression in silver birch shoot endodermis 
    Tirkkonen, Paulina (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.
  • The role of MONOPTEROS and other auxin response factors in root secondary development 
    Lyu, Munan (2019)
    With the aggravation of global environmental problems and the reduction of finite reserved fossil fuels, seeking for alternative energy sources has become one of the priorities for the sustainable development of human society. Vascular plants save the biomass mainly as the form of xylem (also called as wood), which is now considered as an ideal environmental-friendly energy resource. Wood is now being used as renewable biofuels, Biomass composites to replace plastic and so on. The lateral meristem vascular cambium gives rise to xylem and phloem, contributes to the radial growth of plants. Dr. Mähönen’s group choose Arabidopsis root as a model to understand the growth dynamics of vascular cambium. Auxin is essential for various plant developmental processes. The transcription factor family AUXIN RESPONSE FACTOR (ARF) is an important component in auxin signaling pathway, among which AUXIN RESPONSE FACTOR5 (ARF5)/MONOPTEROS (MP) has been discovered to be essential in various plant developmental processes. The first part of my thesis work mainly focuses on analyzing the expression of ARFs during Arabidopsis root secondary development by using both histological reporter GUS and green fluorescent protein GFP. The second part is screening the secondary growth phenotype among the arf knock out mutants. As mp mutant fails to form primary root, artificial microRNA technique is applied to inhibit MP expression in transcriptional level, this construct was established in an XVE inducible system and driven by a broadly expressed promoter to specifically inhibit MP expression at the secondary development stage. I overexpressed amiMP in both wild type background and arf7,19 double mutant background. These three ARFs have strong expressions in cambium and they might function redundantly to regulate cambium activity. Our preliminary results suggest that ARFs function redundantly in regulating root secondary growth, ARF1 and ARF2 together are functional in regulating vascular pattern formation, and ARF16 can repress the root secondary growth and secondary xylem formation. MP is proved to regulate cambium activity and secondary xylem formation by controlling various auxin-response genes, ARF7 and ARF19 might also participate in this process.

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