Study on Light Qualities and Photoreceptors Involved in the Induction of Root Waving in Rice Seedlings

光除了是植物重要之能量來源外，亦是影響植物外觀型態之重要環境因子。本實驗室先前研究發現白光下秈型稻臺中在來一號 (Oryza sativa L. cv. Taichung Native 1；TCN1) 之幼苗種子根會呈現波動狀外觀；稉型稻臺農六十七號 (Oryza sativa L. cv. Tainung 67；TNG67) 之幼苗種子根於白光下則發展為直根型態。另外，我們亦發現一氧化氮、脂氧化物 (oxylipins)、乙烯、生長素依序參與在光照下誘導波動根發生之訊息傳遞途徑中。本研究利用此訊息傳遞途徑探討造成品種間種子根光型態差異可能之原因，發現TCN1對光照刺激及其下游訊息傳遞物較為敏感， 其種子根延長受光照抑制之程度、OsHY5基因表現受光照誘導倍率、訊息分子生合成受光照誘導倍率皆較TNG67高。除此之外，我們發現部分光接受體 (OsPHYs、OsPHOT1a、OsPHOT1b) 於光照及黑暗下之基因表現趨勢符合品種間根部外觀之趨勢。進一步以單光試驗及複合光試驗探討何種光質因子調控波動根發生之分析中，我們發現紅藍綠混光及藍綠混光可模擬出TCN1於白光下之波動根型態，且OsPHOT1a、OsPHOT1b基因表現趨勢符合不同光質下根部外觀型態之趨勢。然而在探討品種間種子根型態差異之生態意義上，我們在固著力試驗結果中發現TCN1植株之固著能力於黑暗或光照下兩者無差別，反之光照下TNG67植株之固著能力明顯低於黑暗處理組。Light is not only the energy source for plants, but also an environmental signal to modulate plant morphogenesis. Our previous research showed that TCN1 (Oryza sativa L. cv. Taichung Native 1; an indica-type rice variety) displayed a wavy root phenotype under light conditions, but TNG67 (Oryza sativa L. cv. Tainung 67; a japonica-type rice variety) displayed a straight root phenotype. Moreover, nitric oxide, oxylipins, ethylene, and auxin were sequentially involved in the signaling cascades of light-induced root waving. In this study, we tried to clarify the mechanism leading to varietally dissimilar seminal root photomorphogenesis. Our results showed that TCN1 was more sensitive to light stimulus and following downstream signaling molecules. Moreover, the levels of light-induced inhihibition of root elongation, gene expression of OsHY5, and biosynthesis of signaling molecules in TCN1 could be higher than those in TNG67. In addition, the gene expression patterns of some photoreceptors (OsPHYs, OsPHOT1a, OsPHOT1b) were correlated to the root phenotypes between varieties under light or dark condition. The effects of the specific wavelength of light on root waving induction were also identified. The results showed that root waving can be induced by red-green-blue and green-blue light. The gene expression patterns of OsPHOT1a and OsPHOT1b were correlated to the root phenotypes under different light qualities. For evaluation of environmental significance of different root morphogenesis; however, it was found that TCN1 seedlings under light or dark conditions performed same anchorage strength. On the other hand, TNG67 seedlings under light condition performed weaker anchorage strength than under dark condition