Browsing by Subject "cambium"

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.

A well-adjusted regulation of vascular development is crucial for plant growth and development. CLASS III HOMEODOMAIN LEUCINE ZIPPER (HD-ZIP III) genes play a decisive role in cambial stem-cell maintenance, xylem cell fate determination, and ensuring proper patterning of vasculature. LITTLE ZIPPER (ZPR) microproteins are involved in the post-translational regulation of HD-ZIP III via a negative feedback mechanism. The protein-protein docking has predicted that HD-ZIP III and ZPR interact at the b-ZIP domain, which is an evolutionarily conserved region. The expression and mutant phenotype of ZPR in root vasculature haven’t been previously described. In this study, we developed the reporter lines and checked the expression in the Arabidopsis root. ZPR1 and ZPR3 showed a distinct and continuous expression from root tip to elongation and differentiation zone. In the cross-section, the expression was detected in cambium and xylem cells. Unlike ZPR1, ZPR3 showed a stronger expression towards the phloem side. Although ZPR2 didn’t show any endogenous expression, expression was detected in the primary root tip and lateral root initiation site upon xylemin treatment. Exogenous auxin application increased the expression of ZPR3, but it required a longer response time. The expression results suggest that ZPR follows the HD-ZIP III expression pattern, however, each ZPR shows some variation from the others. In the mutant analysis, zpr1 showed increased cellular proliferation in the vasculature, but zpr2 had no difference compared to the wild type. The results suggest that ZPR and HD-ZIP III have their function in a similar region in the root vasculature. However, further empirical evidence is necessary to elucidate the interaction of HD-ZIP III and ZPR, and its role in the regulation of root vascular development.

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.