拟南芥ACOL8基因在乙烯合成与响应中的功能分析

植物激素乙烯在多种生理生化过程中发挥重要作用，但其在特定组织器官中的合成机制尚不完全清楚。拟南芥中存在12个功能未知的ACC氧化酶类似蛋白（ACO-like homolog，ACOL），运用基因定点编辑技术构建了ACOL8的功能丧失型突变体，发现该基因的突变削弱了经典的乙烯“三重反应”。与野生型相比，突变体黄化幼苗下胚轴及主根的长度显著增加，这与突变体对外源ACC的敏感性下降现象一致。同时还发现ACOL8基因的表达受乙烯信号的正反馈调控，EIN3过表达增强其表达水平，而etr1-3的突变则产生相反效应。再者，在正常条件下，ACOL8基因的突变并未影响拟南芥的生长；但在盐胁迫条件下，突变体的根冠比显著下降，这说明该基因参与植物的盐胁迫响应。综上，这些结果说明ACOL8可能具有ACC氧化酶的功能，参与乙烯的合成与响应。

Functional Analysis of ACOL8 Gene in the Ethylene Synthesis and Response in Arabidopsis thaliana

The plant hormone ethylene plays pivotal roles in various physiological and biochemical processes. However, the mechanisms controlling its synthesis in certain tissues and organs are not completely understood. There are 12 ACC oxidase homologs（ACO-like homolog, ACOL）of unknown functions in Arabidopsis thaliana. The loss-of-function mutants of ACOL8 gene were constructed using site-directed gene editing technology. It was found that the mutations of this gene attenuated the classical ethylene triple response. Compared with wild type, the mutants showed significant increases in the length of hypocotyls and primary roots of etiolated seedlings, which was consistent with the observation that the mutants had decreased sensitivity to exogenous ACC. Additionally, it was evident that the expression of this gene was subjected to positive feedback regulation of ethylene signaling, as exemplified by the finding that overexpression of EIN3 increased the expression of ACOL8 gene, whereas the etr1-3 muation exerted the opposite effect. Furthermore, the mutation of ACOL8 gene did not appear to affect the growth of A. thaliana under normal conditions, whereas the root-shoot ratio of the mutants decreased significantly under salt stress conditions, suggesting its involvement in plant salt stress response. Collectively, these results indicate that ACOL8 may function as an ACC oxidase to medaite ethylene synthesis and response.