In plants, 3´,5´-cyclic adenosine monophosphate (cAMP) is an important second messenger with varied functions; however, only a few adenylyl cyclases (ACs) that synthesize cAMP have been identified. Moreover, the biological roles of ACs/cAMP in response to stress remain largely unclear. In this study, we used quantitative proteomics techniques to identify a maize heat-induced putative disease-resistance RPP13-like protein 3 (ZmRPP13-LK3), which has three conserved catalytic AC centres. The AC activity of ZmRPP13-LK3 was confirmed by in vitro enzyme activity analysis, in vivo RNAi experiments, and functional complementation in the E. coli cyaA mutant. ZmRPP13-LK3 is located in the mitochondria. The results of in vitro and in vivo experiments indicated that ZmRPP13-LK3 interacts with ZmABC2, a possible cAMP exporter. Under heat stress, the concentrations of ZmRPP13-LK3 and cAMP in the ABA-deficient mutant vp5 were significantly less than those in the wild-type, and treatment with ABA and an ABA inhibitor affected ZmRPP13-LK3 expression in the wild-type. Application of 8-Br-cAMP, a cAMP analogue, increased heat-induced expression of heat-shock proteins in wild-type plants and alleviated heat-activated oxidative stress. Taken together, our results indicate that ZmRPP13-LK3, a new AC, can catalyse ATP for the production of cAMP and may be involved in ABA-regulated heat resistance.

中文翻译：

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一种新的腺苷酸环化酶，即假定的抗病RPP13样蛋白3，参与了脱落酸介导的玉米对热胁迫的抗性

在植物中，3'，5'-环磷酸腺苷（cAMP）是重要的第二信使，具有多种功能。然而，仅鉴定出少数几个合成cAMP的腺苷酸环化酶（AC）。此外，ACs / cAMP在应对压力方面的生物学作用仍不清楚。在这项研究中，我们使用定量蛋白质组学技术来鉴定玉米热诱导的抗病性RPP13样蛋白3（ZmRPP13-LK3），该蛋白具有三个保守的催化AC中心。ZmRPP13-LK3的AC活性已通过体外酶活性分析，体内RNAi实验以及大肠杆菌cyaA突变体的功能互补得到证实。ZmRPP13-LK3位于线粒体中。结果在体外和体内实验表明ZmRPP13-LK3与可能的cAMP出口者ZmABC2相互作用。在热胁迫下，ABA缺陷型突变体vp5中ZmRPP13-LK3和cAMP的浓度显着低于野生型，而ABA和ABA抑制剂处理会影响野生型ZmRPP13-LK3的表达。应用cAMP类似物8-Br-cAMP，可提高野生型植物中热激蛋白的热诱导表达并减轻热激活的氧化应激。两者合计，我们的结果表明，ZmRPP13-LK3，一种新的AC，可以催化ATP产生cAMP，并可能参与ABA调节的耐热性。