Cheng Zhenyu, Duncker Bernard P, McConkey Brendan J, Glick Bernard R
Department of Biology, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L3G1, Canada.
Can J Microbiol. 2008 Feb;54(2):128-36. doi: 10.1139/w07-128.
One of the major mechanisms that plant growth-promoting bacteria use to facilitate plant growth is through the lowering of plant ethylene levels by the bacterial enzyme 1-aminocyclopropane-1-carboxylate (ACC) deaminase. Many of the bacterial ACC deaminase genes (acdS) that have been examined to date are under the transcriptional control of a leucine-responsive regulatory protein, Lrp, encoded by acdR and referred to here as AcdR. The work presented here is focused on how AcdR and the newly discovered AcdB protein from Pseudomonas putida UW4 are involved in the regulation of acdS expression. First, the results of gel retardation experiments showed that AcdR binds to the acdS regulatory region, and this binding activity in vitro is not affected by the addition of 2 mmol x L-1 ACC but can be eliminated by addition of 20 microg x mL-1 leucine. Second, a potential regulatory protein, AcdB, involved in the regulation of acdS expression, was identified through both yeast 2-hybrid screen and coimmunoprecipitation based on its ability to bind to AcdR; subsequently, its binding to the acdS regulatory region in the presence of ACC was shown by gel retardation experiments. The data are interpreted in terms of a model in which AcdR and AcdB co-regulate the expression of the acdS gene.
促进植物生长的细菌促进植物生长的主要机制之一是通过细菌酶1-氨基环丙烷-1-羧酸（ACC）脱氨酶降低植物乙烯水平。迄今为止所检测的许多细菌ACC脱氨酶基因（acdS）受亮氨酸响应调节蛋白Lrp的转录控制，Lrp由acdR编码，此处称为AcdR。本文介绍的工作重点是研究恶臭假单胞菌UW4中的AcdR和新发现的AcdB蛋白如何参与acdS表达的调控。首先，凝胶阻滞实验结果表明AcdR与acdS调控区结合，体外这种结合活性不受添加2 mmol·L-1 ACC的影响，但添加20 μg·mL-1亮氨酸可消除这种活性。其次，基于其与AcdR结合的能力，通过酵母双杂交筛选和免疫共沉淀鉴定出一种参与acdS表达调控的潜在调节蛋白AcdB；随后，凝胶阻滞实验表明其在ACC存在下与acdS调控区结合。这些数据根据AcdR和AcdB共同调节acdS基因表达的模型进行解释。
