阿拉伯芥中APYs與PATL4的交互作用共同調節植物逆境反應

Abstract

當植物處於逆境時，會釋放如胞外ATP等damage-associated molecular patterns (DAMP)，並引發reactive oxygen species (ROS)的累積形成與植物激素共同調節其生理反應的信號。目前研究發現植物Apyrases (APYs)具有降低胞外ATP濃度的功能，且參與植物的(非)生物逆境反應，但APYs在逆境反應中的分子功能尚未完全了解。這篇研究中，我們透過共免疫沉澱、雙分子螢光互補，和酵母雙雜交實驗發現，阿拉伯芥的APY1會與PATELLIN4 (PATL4)交互作用。目前研究發現PATL4是PATL家族的成員且參與PIN1的復極化以調控生長素的運輸。我們想進一步探討PATL4是否與APYs交互作用並共同調節逆境反應。在酵母雙雜交實驗中，我們發現PATL4透過其C端結構域與APYs的穿膜區域交互作用。而在阿拉伯芥原生質體中，APY1和PATL4共同表現於高基氏體。在鹽逆境耐受性實驗下，大量表現APY1或PATL4的轉殖株在鹽逆境中其根部生長較佳，並且具有較少的葉片黃化現象。我們進一步測定了植物體內ROS累積量和ROS反應基因的表現，發現突變株在正常條件下具有更高的ROS積累以及ZAT10和ZAT12的表現，這可能是突變株對逆境耐受性較低的因素之一。此外，APY1/patl2456和PATL4/apy1apy2在鹽逆境下均表現出較APY1-OE和 PATL4-OE更弱的逆境抗性，例如較短的根長以及較高的葉片黃化率。綜上所述，PATL4可能與APYs相互作用以調節植物中ROS信號傳導並提高植物的逆境耐受性。

Plants will release damage-associated molecular patterns (DAMPs) such as extracellular ATP (eATP) for inducing the accumulation of reactive oxygen species (ROS) as signals to co-regulate plant physiological responses with plant hormones when suffering environmental stress. Apyrases (APYs) function in decreasing the level of extracellular ATP and are reported to be involved in both biotic and abiotic stress response in plants. However, the molecular functions of APYs in stress response is still unclarified. In this study, we show that PATELLIN4 (PATL4) interacts with Arabidopsis APY1 using co-immunoprecipitation, bimolecular fluorescence complementation assays, and yeast two-hybrid assays. PATL4 is a member of PATL family that has been reported to promote PIN1 repolarization in response to auxin. Here, we found that PATL4 interacts with the transmembrane region of APYs through its C-terminal domain. In Arabidopsis protoplasts, APY1 and PATL4 co-localize in the Golgi bodies. In our salt stress tolerance tests, both APY1 and PATL4 overexpression line showed better root growth and greening under salt stress. We further examined the ROS accumulation and ROS responsive gene expression, and found that the mutant lines had higher ROS accumulation and ZAT10 and ZAT12 expressions under normal condition, which might be one of the factors making the mutants less stress tolerant. In addition, both APY1/patl2456 and PATL4/apy1apy2 show more sensitive phenotypes under salt stress compared with APY1-OE and PATL4-OE. In conclusion, PATL4 might interact with APYs to maintain the ROS signaling in plants and improve plant stress tolerance.