Fu Jia, Yu Qiyuan, Zhang Chenxi, Xian Baohang, Fan Jie, Huang Xin, Yang Wen, Zou Xiuping, Chen Shanchun, Su Liyan, He Yongrui, Li Qiang
Citrus Research Institute, Southwest University/Chinese Academy of Agricultural Sciences, Beibei, Chongqing 400712, China.
Citrus Research Institute, Southwest University/Chinese Academy of Agricultural Sciences, Beibei, Chongqing 400712, China; National Citrus Engineering Research Center, Beibei, Chongqing 400712, China; National Citrus Improvement Center, Beibei, Chongqing 400712, China.
Int J Biol Macromol. 2023 Feb 28;229:964-973. doi: 10.1016/j.ijbiomac.2022.12.311. Epub 2022 Dec 30.
Citrus bacterial canker (CBC) is a serious bacterial disease affecting citrus plantations and the citrus industry all over the world. We have previously shown that an apetala 2/ethylene response factor in Citrus sinensis, CsAP2-09, positively regulated resistance to CBC, although the regulatory mechanisms remained undetermined. Here, we demonstrated that CsAP2-09 positively and sustainably controlled resistance to CBC in three-year transgenic plants. CsAP2-09 was found to be a transcriptional activator, and qRT-PCR and dual luciferase assays showed that it controlled the expression CsGH3.1L. CsAP2-09 bound directly to the promotor of CsGH3.1L, shown by yeast one-hybrid assay, with the binding site confirmed by electrophoretic mobility shift assay. Biochemical assays showed that CsAP2-09 negatively regulated the biosynthesis of indole acetic acid (IAA) and positively regulated that of salicylic acid (SA) and ethylene, verified with transient overexpression of CsGH3.1L. The combination of these results with those of previous reports indicated that SA, ethylene, and IAA can directly regulate CBC resistance. Overall, we revealed a pathway whereby CsAP2-09 conferred CBC resistance by direct binding to the CsGH3.1L promoter, activating its expression and modulating IAA, SA, and ethylene biosynthesis. Our study indicates the potential value of manipulating CsAP2-09 and CsGH3.1L in the breeding of CBC-resistant citrus.
柑橘溃疡病（CBC）是一种严重的细菌性病害，影响着世界各地的柑橘种植园和柑橘产业。我们之前已经表明，甜橙中的一个AP2/乙烯反应因子CsAP2-09对柑橘溃疡病抗性具有正向调控作用，尽管其调控机制尚不清楚。在此，我们证明了CsAP2-09在三年生转基因植株中对柑橘溃疡病抗性具有正向且持续的控制作用。发现CsAP2-09是一种转录激活因子，qRT-PCR和双荧光素酶分析表明它调控CsGH3.1L的表达。酵母单杂交分析表明CsAP2-09直接与CsGH3.1L的启动子结合，电泳迁移率变动分析确定了结合位点。生化分析表明CsAP2-09对吲哚乙酸（IAA）的生物合成具有负调控作用，对水杨酸（SA）和乙烯的生物合成具有正调控作用，CsGH3.1L的瞬时过表达验证了这一点。这些结果与之前报道的结果相结合表明，SA、乙烯和IAA可以直接调控柑橘溃疡病抗性。总体而言，我们揭示了一条途径，即CsAP2-09通过直接结合CsGH3.1L启动子、激活其表达并调节IAA、SA和乙烯生物合成来赋予柑橘溃疡病抗性。我们的研究表明了在抗柑橘溃疡病柑橘育种中操纵CsAP2-09和CsGH3.1L的潜在价值。
