AtWRKY54 與 AtWRKY70 在熱逆境下的功能性分析

Abstract

熱逆境會對植物生長造成不利的影響，因此研究植物體內耐熱的基因是一項 很重要的課題。利用微陣列分析技術，比較正常生長與處理熱逆境的阿拉伯芥基 因的表現差異，選取兩個轉錄因子 AtWRKY54 (AT2G40750)與 AtWRKY70 (AT3G56400)。此二基因的表現量均受到熱逆境所抑制。利用此基因缺失與大量表 現的轉殖株做一連串的生理分析。偵測植物體內過氧化氫累積的情形，大量表現 AtWRKYY54 有助於減低因熱所產生的過氧化氫累積，而在大量表現 AtWRKY70 的轉殖株當中則無此現象，但若此基因發生缺失則會使過氧化氫在常溫或高溫下有 不正常累積的情形。進一步分析植物體內部份抗氧化酵素的活性是否有受到影響， 並無觀察到明顯的差異。高溫逆境下常會伴隨著脂質的過氧化產生有毒物質丙二 醛，不利植物的正常生理代謝，因此利用偵測丙二醛累積的情形判斷植株受熱逆 境的傷害程度，AtWRKY54 與 AtWRKY70 大量表現的轉殖株中，丙二醛累積量皆有明顯的下降。在植物耐熱性測試方面，大量表現 AtWRKY54 可以使植株在熱逆境的情況下有較好的生長與存活能力，大量表現 ATWRKY70 無明顯差異，但此基因缺失會造成植物基礎的耐熱能力下降。綜合以上結果，AtWRKY54 可以減少過氧化氫的累積與穩定細胞膜構造，使植物在熱逆境下可以獲得比較好耐熱性，而 ATWRKY70 的效果則比較次要。

Heat stress causes severe damage in plants. We used microarray to analyze the difference of gene expression between heat and non-heat treated Arabidopsis. Two heat stress related transcription factors, AtWRKY54 (AT2G40750) and AtWRKY70 (AT3G56400) were chosen for further study. The expression levels of AtWRKY54 and AtWRKY70 reduced in heat stress. Over-expression AtWRKY54 would decrease hydrogen peroxide accumulation that caused by heat stress. No obvious effect exists in AtWRKY70 overexpression plants, but defect in AtWRKY70 could increase hydrogen peroxide accumulation. However, AtWRKY54 and AtWRKY70 did not participate in the regulation of antioxidant enzymes. In addition, AtWRKY54 and AtWRKY70 could stabilize cell membrane during heat stress. Over-expressing AtWRKY54 further enhanced hypocotyl growth and showed higher survival rate than that of wild type after heat shock. Over-expressing AtWRKY70 revealed better hypocotyl growth than wild type. Conclusively, AtWRKY54 might decrease ROS generation and stabilize cell membrane in heat stress. AtWRKY70 could not decrease ROS generation, but it may still involve in cell membrane stability.