Han Yunlei, Wang Rui, Yang Zhirong, Zhan Yuhua, Ma Yao, Ping Shuzhen, Zhang Liwen, Lin Min, Yan Yongliang
Key Laboratory of Bio-resources and Eco-environment Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, Sichuan 610064, P.R. China.
Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, P.R. China.
J Microbiol Biotechnol. 2015 Jul;25(7):1119-28. doi: 10.4014/jmb.1412.12053.
1-Aminocyclopropane-1-carboxylate (ACC) deaminase, which is encoded by some bacteria, can reduce the amount of ethylene, a root elongation inhibitor, and stimulate the growth of plants under various environmental stresses. The presence of ACC deaminase activity and the regulation of ACC in several rhizospheric bacteria have been reported. The nitrogen-fixing Pseudomonas stutzeri A1501 is capable of endophytic association with rice plants and promotes the growth of rice. However, the functional identification of ACC deaminase has not been performed. In this study, the proposed effect of ACC deaminase in P. stutzeri A1501 was investigated. Genome mining showed that P. stutzeri A1501 carries a single gene encoding ACC deaminase, designated acdS. The acdS mutant was devoid of ACC deaminase activity and was less resistant to NaCl and NiCl2 compared with the wild-type. Furthermore, inactivation of acdS greatly impaired its nitrogenase activity under salt stress conditions. It was also observed that mutation of the acdS gene led to loss of the ability to promote the growth of rice under salt or heavy metal stress. Taken together, this study illustrates the essential role of ACC deaminase, not only in enhancing the salt or heavy metal tolerance of bacteria but also in improving the growth of plants, and provides a theoretical basis for studying the interaction between plant growth-promoting rhizobacteria and plants.
1-氨基环丙烷-1-羧酸（ACC）脱氨酶由某些细菌编码，它可以减少根伸长抑制剂乙烯的量，并在各种环境胁迫下刺激植物生长。已有报道称几种根际细菌中存在ACC脱氨酶活性以及ACC的调控情况。固氮斯氏假单胞菌A1501能够与水稻植株形成内生关联并促进水稻生长。然而，尚未对ACC脱氨酶进行功能鉴定。在本研究中，对斯氏假单胞菌A1501中ACC脱氨酶的假定作用进行了研究。基因组挖掘表明，斯氏假单胞菌A1501携带一个编码ACC脱氨酶的单基因，命名为acdS。与野生型相比，acdS突变体缺乏ACC脱氨酶活性，并且对NaCl和NiCl2的耐受性较低。此外，在盐胁迫条件下，acdS的失活极大地损害了其固氮酶活性。还观察到，acdS基因突变导致在盐胁迫或重金属胁迫下促进水稻生长的能力丧失。综上所述，本研究阐明了ACC脱氨酶不仅在增强细菌对盐或重金属的耐受性方面，而且在促进植物生长方面都起着至关重要的作用，并为研究植物促生根际细菌与植物之间的相互作用提供了理论依据。
