2013 Fiscal Year Annual Research Report
| Project/Area Number |
13J01792
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| Research Institution | Osaka University |
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Principal Investigator |
チヤン イエ 大阪大学, 理学研究科, 特別研究員(DC1)
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| Keywords | plant development / xylem-pole pericycle / lateral root development |
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| Research Abstract |
In this first year of my study, I have completed most the preliminary screening of all the XPP-related candidate genes. I have cloned and overexpressed all the candidate genes in the XP-pericycle specific GFP marker plant J0121 and check the expression pattern of the GFP marker in the transformants. All the TF-coding candidate genes were grouped by their sequence similarities and their expression patterns and knock-out mutant phenotypes were analyzed according to the phylogenic tree.
I have been continued focusing on the candidate gene No. 17, which had been shown to positively regulate XPP cell identity and lateral root development possibly through modulation of auxin transportation. Ubiquitous expression of No. 17-VP16 altered expression patterns of several cell-type specific markers (e.g. SUC2-GFP as companion cell markers in the phloem) and cellular responsive reporters (e.g. TCS-GFP as cytokinin responsive reporter), suggesting disruptions in cell identity and cellular behavior. Be
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sides, increased xylem cell number and abnormal xylem cell pattern were observed in No. 17-SRDX plants, pointing again to the association of XPP specification and xylem development. The expression pattern of No. 17's homolog, No. 17H, overlaps with that of No. 17's, and No. 17H-SRDX plants phenocopy No. 17-SRDX plants, indicating that No. 17 and No. 17H might function redundantly. However, Double knock-out mutant no. 17no. 17h has no visible phenotype in root, indicating the existence of more redundant factors.
According to the promoter activity analysis, No. 17 is expressed in the pericycle, but not confined to XPP, in root. While translational fusion GFP reporter shows that No. 17-GFP protein first stays in the cytoplasm and then goes into the nuclei in the maturation zone. This led to the thinking that No. 17 may recruit co-factors, and together with its partners, they function specifically to regulate XPP cell identity. No. 17 belongs to the bHLH protein family, of which the protein often forms dimers with another bHLH protein in order to bind to DNA. Extensive study on the bHLH TF-coding candidate genes revealed another player in regulating pericycle cell identity : No. 51. Interestingly, simply overexpression of No. 51 could cause ectopic expression of XPP-specific GFP in J0121. Auxin treatment induced cell division of GFP-expressing cells in root epidermis. Lateral root formation was also affected in the No. 51-overexpressing plants. No. 51 is expressed specifically in the nuclei of mature XPP cells. Exploring the interaction of these involved transcription factors may serve to reveal the regulating mechanism of pericycle cell identity. Less
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
In this year, I have completed the preliminary screening of all the candidate genes as planned. And I have identified a very promising candidate gene, No. 51. However, the knock-out mutant analysis was lagging behind the plan for two reasons, the unavailability of T-DNA insertion lines of several of my candidate genes, and the time-consuming process of crossing to make double and multiple mutants.
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| Strategy for Future Research Activity |
In the coming second year. I will adjust my research plan according to the results of last year. Since I have completed the preliminary screening, I will focus on the promising candidate genes that I have identified last year, including No. 17 and its homolog No. 17H (and other 2 genes close in sequence similarity with No. 17, No. 17H2 and No. 17H3), and other bHLH TF-coding genes No. 51, No. 13, No. 14, and No. 36. Crossing for the double and multiple mutants in different combinations of them would be prioritized since its the most time-consuming. To determine the possible interaction between these bHLH genes, methods like yeast-2 hybrid and IP-MS are being considered. Some necessary transgenic lines would be created and more hormone treatment experiments shall be performed to generate more supportive data for the future publication.
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Research Products
(2 results)
