Abstract：
The WRKY transcription factor (TF) genes form a large family in higher plants, with 72 members in Arabidopsis (Arabidopsis thaliana). The gaseous phytohormone ethylene (ET) regulates multiple physiological processes in plants. It is known that 1-aminocyclopropane-1-carboxylic acid (ACC) synthases (ACSs, EC 4.4.1.14) limit the enzymatic reaction rate of ethylene synthesis. However, whether WRKY TFs regulate the expression of ACSs and/or ACC oxidases (ACOs, EC 1.14.17.4) remains largely elusive. Here, we demonstrated that Arabidopsis WRKY22 positively regulated the expression of a few ACS and ACO genes, thus promoting ethylene production. Inducible overexpression of WRKY22 caused shorter hypocotyls without ACC treatment. A qRT-PCR screening demonstrated that overexpression of WRKY22 activates the expression of several ACS and ACO genes. The promoter regions of ACS5, ACS11, and ACO5 were also activated by WRKY22, which was revealed by a dual luciferase reporter assay. A follow-up chromatin immunoprecipitation coupled with quantitative PCR (ChIP-qPCR) and electrophoretic mobility shift assay (EMSA) showed that the promoter regions of ACS5 and ACO5 could be bound by WRKY22 directly. Moreover, wrky22 mutants had longer primary roots and more lateral roots than wild type, while WRKY22-overexpressing lines showed the opposite phenotype. In conclusion, this study revealed that WRKY22 acts as a novel TF activating, at least, the expression of ACS5 and ACO5 to increase ethylene synthesis and modulate root development.
摘要：
WRKY转录因子(TF)基因在高等植物中形成一个家族,拟南芥（拟南芥）有72名成员。气态植物激素乙烯（ET）调节植物的多种生理过程。已知1-氨基环丙烷-1-羧酸（ACC）合酶（ACSs，EC4.4.1.14)限制乙烯合成的酶促反应速率。然而,WRKYTFs是否调节ACSs和/或ACC氧化酶的表达(ACOs，EC1.14.17.4）在很大程度上仍然难以捉摸。这里,我们证明拟南芥WRKY22正调控一些ACS和ACO基因的表达，从而促进乙烯生产。WRKY22的诱导型过表达在没有ACC处理的情况下引起较短的下胚轴。qRT-PCR筛选证明WRKY22的过表达激活了几个ACS和ACO基因的表达。ACS5，ACS11和ACO5的启动子区域也被WRKY22激活，这通过双荧光素酶报告基因测定得以揭示。随后的染色质免疫沉淀结合定量PCR（ChIP-qPCR）和电泳迁移率变化测定（EMSA）表明，ACS5和ACO5的启动子区域可以直接与WRKY22结合。此外，wrky22突变体比野生型具有更长的主根和更多的侧根，而WRKY22过表达的品系表现出相反的表型。总之,这项研究表明，WRKY22作为一种新型的TF激活，至少,ACS5和ACO5的表达可增加乙烯合成并调节根系发育。
