水稻Oshk4-2突變體之特性分析

Studies on the characterization of rice histidine kinase mutant (Oshk4-2)

葉瑞恩(Jui-En Yeh)

指導教授 ： 蔡育彰

國立臺灣大學/生物資源暨農學院/農藝學研究所/碩士(2015年)

https://doi.org/10.6342/NTU.2015.01158

摘要

細胞分裂素調節植物在環境因子下的生長與發育，而細胞分裂素接受器是負責與細胞分裂素結合並且啟動下游訊息傳遞的第一個蛋白質單元，其胺基酸結構中具有跨膜區域，因此細胞分裂素接受器有可能當作一個偵測環境變化的感應器。水稻是世界上重要的糧食作物之一，在幼苗與開花期遭遇高溫逆境會顯著影響其生長與稔實率。熱逆境會造成膜系的流動性發生劇烈變化，可能因破壞細胞平衡而導致植物受傷害。因此，本研究針對是否細胞分裂素接受器在受熱衝擊處理之 下，會影響植物性狀以及其耐熱性來探討。利用細胞分裂素接受器缺失株 Oshk4-2，我們發現 OsHK4 參與幼苗時期調控葉長度與葉角度，以及在葉片老化中扮演負向調控的角色。此外，在熱逆境之下，OsHK4 缺失會顯著降低存活率，基因層次上，細胞分裂素訊息受抑制且小分子熱休克蛋白基因也同時被抑制；生理層次上，抗氧化酵素 APX 活性顯著降低，GR可能因構型改變而使活性降低，而光合 作用能力 ?PSII 也快速降低。由上述結果推論，水稻細胞分裂素接受器 OsHK4 在幼苗時期除了參與調控葉型態與葉片老化過程，另外在熱逆境之下也同時調控細胞分裂素訊息傳遞、抗氧化系統以及光合作用能力，進而影響水稻的耐熱性。

關鍵字

細胞分裂素訊息傳遞 ； 組胺酸激酶 ； 熱衝擊反應 ； 小分子熱休克蛋白 ； 耐熱性

並列摘要

Cytokinin signaling regulates plant growth and development by several environmental cues. The cytokinin receptor, histidine kinase (HK) is responsible for the first component to bind with cytokinin and then activates downstream cytokinin signal transduction. As characterized to have the transmembrane domain in amino acid sequence, cytokinin receptor may serve the sensor for environmental fluctuation. Rice is one of the most important cereal crops in the world and is a heat-sensitive plant during seedling and flowering stages. Heat stress causes intensive change of membrane fluidity. Therefore, this study focuses on whether cytokinin receptors response to heat stress to result in plant phenotype change or different in thermotolerance. By using cytokinin receptor mutant, Oshk4-2, we found that OsHK4 regulates leaf length and leaf angle and serves as the negative regulator on leaf senescence at the seedlings stage. Moreover, defect in OsHK4 significantly decreases the survival rate after heat stress. The induction of the transcript level of cytokinin signaling genes and small heat stress protein (sHSP) are repressed after heat stress treatment in OsHK4 defect mutant. The activity of antioxidant enzymes, ascorbate peroxidase (APX) and glutathione reductase (GR) are reduced and the ?PSII rapid decreased after heat stress in OsHK4 defect mutant. These results suggest OsHK4 regulates early seedling growth and mediates part of CK signaling transduction, antioxidant system and photosynthesis with influence on thermotolerance after heat stress at the seedling stage.

並列關鍵字

Cytokinin signaling ； Histidine kinase ； Heat stress response ； small heat stress proteins ； thermotolerance

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