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標題: | 穀胱甘肽還原酶在水稻充實期高溫下對稻米品質形成扮演之角色 Roles of glutathione reductase on grain quality formation of rice (Oryza sativa L.) at grain-filling stage under high temperature stress |
作者: | Cheng-Hui Yang 楊澄慧 |
指導教授: | 盧虎生(Huu-Sheng Lur) |
關鍵字: | 高溫,稻米品質,穀胱甘?還原?,抗壞血酸過氧化?,抗氧化酵素,氧化逆境, high temperature,grain quality,glutathione reductase,ascorbate peroxidase,antioxidant enzymes,oxidative stress, |
出版年 : | 2014 |
學位: | 碩士 |
摘要: | 水稻充實期特別容易受到高溫的影響降低水稻的產量與品質,尤其極易產生白堊質,進而降低水稻的外觀品質,一些研究指出,白堊質的產生可能與水稻穎果內的氧化逆境有關,然而機制仍尚未釐清,因此,本試驗以Ascorbate peroxidase 8 (OsAPX8)和Glutathione reductase (OsGR3)兩個抗氧化酵素之突變株(日本晴背景)及大量表現植株(臺農67號背景)探討氧化逆境與稻米白堊質形成之關係。結果顯示,大量表現OsGR3的OEGR7-5轉殖系在高溫處理後能減緩白堊質的產生,具有在高溫下維持優良穀粒外觀品質之潛力,但OsAPX8則無此功能,因此後續試驗僅探討OsGR3與稻米品質之關係。生理分析結果顯示,高溫會加速OsGR3突變株 (osgr3) 穎果充實、減輕穀粒乾重、加速葉綠素的降解並累積較高的H2O2含量,然而OEGR7-5 水稻在高溫處理下乾重和常溫無明顯差異、能夠延遲葉綠素的降解並減緩H2O2的累積。穎果內抗氧化系統分析結果顯示,OEGR7-5在高溫逆境初期有較高GSH/GSSG比值,並維持穩定的GR活性;反之,在高溫下osgr3的GSH/GSSG比值顯著降低。在基因表現方面,高溫會抑制野生型水稻穎果OsGR3表現,並於穎果發育後期抑制澱粉生合成基因Glutamate synthetase、Granule-bound starch synthase 和Prolamin 7、與抗氧化相關基因NADPH oxidase、Mn superoxide dismutase、Catalase B 和Dehydroascorbate reductase的表現,在OEGR7-5品系中能減緩抑制的情形,而osgr3受抑制表現情形更嚴重。無氧呼吸相關基因在高溫下Pyruvate decarboxylase與Alcohol dehydrogenase表現上升,代表能量的供應效率下降。綜合各項分析結果,大量表現OsGR3基因有效減緩高溫所造成的白堊質可能機制為(一),藉由減緩葉綠素的降解,維持stay green現象,減緩高溫所造成能量的大量損耗;(二)抗氧化系統效率提高,降低H2O2的累積,減緩高溫所帶來的氧化逆境。本研究期望能在全球暖化下,對穩定水稻產量與品質之研究提供重要的參考。 High temperature (HT) during rice grain-filling stage facilitates the formation of chalky grains, consequently influences appearance and milling quality. Formation of chalkiness has been correlated to oxidative stress, however the molecular mechanism remains unclear. Therefore, mutants (genetic background: Nipponbare) and overexpression lines (genetic background: Tainung67) of two antioxidant enzymes, Glutathion Reductase 3 (OsGR3) and Ascorbate Peroxidase 8 (OsAPX8), were investigated to reveal their roles in prevention of chalky formation in rice grains under HT. Physiological analysis on OsGR3 mutant (osgr3) reveals that HT aggravates grain filling, reduces grain weight, enhances chlorophyll degradation and increases the accumulation of H2O2 in grains. In contrast, GR overexpression line OEGR7-5 notably reduces chalky grains under HT. Leaves of OEGR7-5 also shows stay-green for a long growth period as compared to wild type (WT). In addition, OEGR7-5 maintains a high GSH/GSSG ratio under HT. In WT, HT represses expression of genes encoding starch and protein synthetic enzymes as well as antioxidant enzymes such as Glutelin synthetase, Granule-bound starch synthase, Prolamin 7, NADPH oxidase, Mn superoxide dismutase, Catalase B and Dehydroascorbate reductase. Conversely, expression of these genes were not reduced until the lately grain formation stage in OEGR7-5 under HT stress. Taken together, OsGR3 gene plays crucial roles in chalky formation of rice grains under HT by maintaining chlorophyll contents in leaves and modulating the homeostasis of antioxidative defence system. These results provide new clues about the stabilization of yield and quality of rice production under global warming condition. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/56553 |
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