Department of Genetics, Faculty of Science, Kasetsart University, Bangkok, 10900, Thailand.
Center for Advanced Studies in Tropical Natural Resources, National Research University-Kasetsart University (CASTNAR, NRU-KU), Bangkok, 10900, Thailand.
Sci Rep. 2018 Jan 31;8(1):1950. doi: 10.1038/s41598-018-19799-9.
1-aminocyclopropane-1-carboxylate deaminase (ACCD)-producing endophytic Streptomyces sp. GMKU 336 and its ACCD-deficient mutant were inoculated into Thai jasmine rice Khao Dok Mali 105 cultivar (Oryza sativa L. cv. KDML105) under salt stress (150 mM NaCl) conditions. The results clearly indicated that Streptomyces sp. GMKU 336 significantly increased plant growth, chlorophyll, proline, K, Ca, and water contents; but decreased ethylene, reactive oxygen species (ROS), Na, and Na/K ratio when compared to plants not inoculated and those inoculated with the ACCD-deficient mutant. Expression profiles of stress responsive genes in rice in association with strain GMKU 336 were correlated to plant physiological characteristics. Genes involved in the ethylene pathway, ACO1 and EREBP1, were significantly down-regulated; while acdS encoding ACCD in Streptomyces sp. GMKU 336 was up-regulated in vivo. Furthermore, genes involved in osmotic balance (BADH1), Na transporters (NHX1 and SOS1), calmodulin (Cam1-1), and antioxidant enzymes (CuZn-SOD1 and CATb) were up-regulated; whereas, a gene implicated in a signaling cascade, MAPK5, was down-regulated. This work demonstrates the first time that ACCD-producing Streptomyces sp. GMKU 336 enhances growth of rice and increases salt tolerance by reduction of ethylene via the action of ACCD and further assists plants to scavenge ROS, balance ion content and osmotic pressure.
1-氨基环丙烷-1-羧酸脱氨酶（ACCD）产生内生链霉菌 GMKU 336 及其 ACCD 缺陷突变体在盐胁迫（150 mM NaCl）条件下接种泰国茉莉香米 Khao Dok Mali 105 品种（Oryza sativa L. cv. KDML105）。结果清楚地表明，与未接种和接种 ACCD 缺陷突变体的植物相比，链霉菌 GMKU 336 显著增加了植物的生长、叶绿素、脯氨酸、K、Ca 和水分含量；但降低了乙烯、活性氧（ROS）、Na 和 Na/K 比。与 GMKU 336 菌株相关的水稻应激响应基因的表达谱与植物的生理特征相关。参与乙烯途径的基因 ACO1 和 EREBP1 显著下调；而链霉菌 GMKU 336 中编码 ACCD 的 acdS 基因在体内上调。此外，参与渗透平衡的基因（BADH1）、Na 转运蛋白（NHX1 和 SOS1）、钙调蛋白（Cam1-1）和抗氧化酶（CuZn-SOD1 和 CATb）上调；而涉及信号级联的基因 MAPK5 下调。这项工作首次证明，ACCD 产生的链霉菌 GMKU 336 通过 ACCD 的作用降低乙烯来增强水稻的生长并提高耐盐性，并进一步帮助植物清除 ROS、平衡离子含量和渗透压。
