阿拉伯芥中NAC78在非生物逆境反應及其與APYs交互作用的功能性研究

Abstract

氣候變遷對植物造成了各種的非生物性壓力，像是高溫、洪水和乾旱，而這些因素對植物的生長和作物的產量將會產生負面影響。植物的APYs (apyrase) 功能是水解細胞外的ATP (eATP)，進而去抑制eATP所誘導的活性氧 (ROS) 訊號途徑並影響逆境反應。我們先前的研究顯示，APY對植物的鹽逆境反應有正向的影響，並可能與有穿膜區域的NAC轉錄因子──NAC78有交互作用。在本篇研究中，我使用Y2H、BiFC和Co-IP方法確認了NAC78與APY之間的交互作用。並且NAC78是利用其C端與APY有交互作用，而缺乏穿膜區域的N端則被發現位於細胞核中。NAC78在非生物性逆境中可能有正向的功能，因為在鹽分和乾旱環境下，nac78突變株表現出根伸長減少和綠葉比例降低的現象。而這些nac78突變株則有更高的逆境反應基因和ROS反應基因的表現量，顯示NAC78參與在非生物性的逆境反應，可能是透過與APY交互作用進而影響ROS訊息傳遞，而非直接調節逆境反應基因的表現。在高溫耐受性測試中，NAC78和APY1/2都對高溫耐受性有正向的影響，在不同的HSF和HSP基因的表現量則有所不同。另外，在NAC78剪切實驗中，APY2似乎影響了NAC78在熱逆境下的蛋白表現。未來的研究將進一步探討NAC78作為轉錄因子的作用，包括其轉錄活性、下游基因的調控，以及NAC78與APYs在非生物逆境環境下的交互作用功能。

Climate change causes a variety of abiotic pressures on plants, such as heat, floods, and droughts, reducing growth and agricultural production. Plant apyrases (APYs) degrade extracellular ATP (eATP), inducing ROS signaling and stress responses. Our recent study demonstrates that APYs favorably regulate plant responses to salt stress and may interact with the membrane-bound NAC transcription factor, NAC78. In this study, I confirmed the interaction between NAC78 and APYs using Y2H, BiFC, and Co-IP methods. The C-terminal region of NAC78 interacts with APYs, while the N-terminal region, lacking a transmembrane motif, localizes in the nucleus. NAC78 plays a positive role in stress responses, as nac78 mutants exhibited reduced root elongation and lower green leaf ratios under salt and drought conditions. The nac78 mutants also showed higher expression levels of stress-responsive and ROS-responsive genes, suggesting that NAC78 might be involved in abiotic stress response through interacting with APY, affecting ROS signaling, but not directly regulating stress-responsive genes expressions. In heat stress tolerance tests, both NAC78 and APY1/2 were found to contribute positively to heat stress tolerance, with varying expression levels of HSF and HSP genes. In the NAC78 cleavage test, APY2 appeared to influence NAC78 function under heat stress. Future research will further explore NAC78’s role as a transcription factor, including its transcriptional activity, regulation of downstream genes, and the significance of the NAC78-APYs interaction under abiotic stress conditions.