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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/81867

    Title: 探討水稻及阿拉伯芥對糖訊息傳導及環境逆境之反應機制;Mechanisms of sugar signaling and environmental stress responses in rice and Arabidopsis
    Authors: 陳逸詩;Chen, Yi-Shih
    Contributors: 生命科學系
    Keywords: 水稻;阿拉伯芥;α澱粉水解酵素;MYB 轉錄因子;環境逆境;產量;rice;Arabidopsis;α-amylase;MYB transcription factors;environmental stress;yield
    Date: 2019-10-30
    Issue Date: 2020-01-07 14:25:16 (UTC+8)
    Publisher: 國立中央大學
    Abstract: 摘 要

    本篇論文的研究目的是了解調控及功能型蛋白的特性及其應用在植物逆境上的應用。本論文主要分為三個章節。第一章主要探討一個胚胎發育後期大量累積的蛋白質(HVA1) 在逆境耐受性中的作用;第二章是研究水稻轉錄因子MYBS2在糖訊息傳導中所扮演的角色;第三章是探討水稻轉錄因子MYBS1的兩個阿拉伯芥同源基因在糖訊息傳導中所扮演的角色。
    自營植物已經進化出獨特的機制來維持糖的平衡。有糖、缺糖相互調控基因表現的開與關是維持糖恆定的主要機制之一,但其細節卻尚不明。α-澱粉水酵素(αAmy)是將澱粉水解為植物生長所需醣類的關鍵酵素,它會被缺糖誘導與有糖抑制。在本章中,αAmy基因表現量的開與關主要是受到兩個MYB轉錄因子競爭同一個啟動子的鍵結位置所調控。在缺糖下,MYBS1促進Amy的表現,而有糖下MYBS2抑制它。缺糖促進MYBS1進核與MYBS2出核,反之有糖則產生相反的效果。MYBS2蛋白質上不同位置的絲氨酸殘基(serine)的磷酸化是調控MYBS2在不同糖環境下的進、出核以及維持其與14-3-3蛋白質的交互作用主要因子。此外,脫水、熱與滲透逆境皆會抑制MYBS2的表現,進而誘導Amy3 表現。最重要的是,大量表現Amy3與抑制MYBS2皆可以增進水稻的生長、逆境的耐受性和單株總粒重。

    The aim of this study is to characterize the regulatory and functional proteins that confer the stress tolerances in plants. The dissertation includes three chapters. The first chapter examines the roles of a late embryogenesis abundant protein (HVA1) in stress tolerance. The second chapter discribes the roles of MYBS2 transcription factor in sugar signaling and stress tolerance in rice. The final chapter demonstrates the roles of two MYB transcription factors in Arabidopsis.
    Regulation of root architecture is essential for maintaining plant growth under adverse environments. Stress/ABA inducible HVA1 was highly accumulated in root apical meristem (RAM) and lateral root primordia (LRP) after ABA/stress treatments, leading to enhanced root system expansion. HVA1 promotes lateral root (LR) initiation, elongation and emergence and primary root (PR) elongation via an auxin-dependent process, particularly by intensifying asymmetrical accumulation of auxin in LRP founder cells and RAM, even under ABA/stress-suppressive conditions. We demonstrate a successful application of an inducible promoter in regulating the spatial and temporal expression of HVA1 for improving root architecture and multiple stress tolerance without yield penalty.
    Autotrophic plants have evolved distinctive mechanisms for maintaining a range of sugars homeostatic states. The on/off switch of reversible gene expression by sugar starvation/provision represents one of the major mechanisms by which sugar levels are maintained, but the details remain unclear. -Amylase (Amy) is the key enzyme for hydrolyzing starch into sugars for plant growth. It is induced by sugar starvation and repressed by sugar provision. In the second chapter, the on/off switch of Amy expression was found to regulate by two MYB transcription factors competing for the same promoter element. MYBS1 promotes Amy expression under sugar starvation, whereas MYBS2 represses it. Sugar starvation promotes nuclear import of MYBS1 and nuclear export of MYBS2, whereas sugar provision has the opposite effects. Phosphorylation of MYBS2 at distinct serine residues plays important roles in regulating its sugar-dependent nucleocytoplasmic shuttling and maintenance in cytoplasm by 14-3-3 proteins. Moreover, dehydration, heat and osmotic stress repress MYBS2 expression, thereby inducing Amy3. Importantly, activation of Amy3 and suppression of MYBS2 enhances plant growth, stress tolerance and total grain weight per plant in rice.
    OsMYBS1 is involved in sugar- and hormone-regulated α-amylase gene expression in rice. In the third chapter, the roles of AtMYBS1 and AtMYBS2, which are OsMYBS1 homologs, in sugar signaling in Arabidopsis were investigated. Germination and seedling growth of atmybs1 mutant were hypersensitive, whereas those of atmybs2 were hyposensitive, to glucose and ABA. Furthermore, the expression of glucose-responsive genes, such as HXK1, CAB1, APL3, and CHS, were up-regulated in the atmybs1 mutant but down-regulated in the mybs2 mutant. Moreover, the mRNA levels of three ABA biosynthesis genes, ABA1, NCED9, and AAO3, and three ABA signaling genes, ABI3, ABI4, and ABI5, were increased upon glucose treatment in atmybs1, but decreased in mybs2, seedlings. These results suggest that AtMYBS1 plays a negative, while AtMYBS2 plays a positive, role in the ABA-dependent sugar repression of germination and seeding development.
    The knowledge, gene, and findings obtained from these studies will help in developing tolerance crop varieties for sustainable agriculture.
    Appears in Collections:[生命科學研究所 ] 博碩士論文

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