Department of Environmental and Biological Chemistry, Chungbuk National University, Cheongju, South Korea.
Microbiome Network and Department of Agricultural Biology, Colorado State University, Fort Collins, Colorado, USA.
Physiol Plant. 2023 Mar;175(2):e13909. doi: 10.1111/ppl.13909.
Pathogenesis-related (PR) signaling plays multiple roles in plant development under abiotic and biotic stress conditions and is regulated by a plethora of plant physiological as well as external factors. Here, our study was conducted to evaluate the role of an ACC deaminase-producing endophytic bacteria in regulating ethylene-induced PR signaling in red pepper plants under salt stress. We also evaluated the efficiency of the bacteria in down-regulating the PR signaling for efficient colonization and persistence in the plant endosphere. We used a characteristic endophyte, Methylobacterium oryzae CBMB20 and its ACC deaminase knockdown mutant (acdS ). The wild-type M. oryzae CBMB20 was able to decrease ethylene emission by 23% compared to the noninoculated and acdS M. oryzae CBMB20 inoculated plants under salt stress. The increase in ethylene emission resulted in enhanced hydrogen peroxide concentration, phenylalanine ammonia-lyase activity, β-1,3 glucanase activity, and expression profiles of WRKY, CaPR1, and CaPTI1 genes that are typical salt stress and PR signaling factors. Furthermore, the inoculation of both the bacterial strains had shown induction of PR signaling under normal conditions during the initial inoculation period. However, wild-type M. oryzae CBMB20 was able to down-regulate the ethylene-induced PR signaling under salt stress and enhance plant growth and stress tolerance. Collectively, ACC deaminase-producing endophytic bacteria down-regulate the salt stress-mediated PR signaling in plants by regulating the stress ethylene emission levels and this suggests a new paradigm in efficient colonization and persistence of ACC deaminase-producing endophytic bacteria for better plant growth and productivity.
植物在非生物和生物胁迫条件下的发育过程中，病程相关（PR）信号发挥多种作用，受大量植物生理和外部因素的调节。在这里，我们的研究旨在评估产 ACC 脱氨酶的内生细菌在盐胁迫下调节红辣椒植株中乙烯诱导的 PR 信号的作用。我们还评估了细菌下调 PR 信号的效率，以实现其在植物内皮层中的有效定植和持久存在。我们使用了一种特征内生菌，即水稻甲基杆菌 CBMB20 及其 ACC 脱氨酶敲低突变体（acdS）。与未接种和接种 acdS 水稻甲基杆菌 CBMB20 的植物相比，野生型水稻甲基杆菌 CBMB20 能够在盐胁迫下将乙烯排放量降低 23%。乙烯排放的增加导致过氧化氢浓度、苯丙氨酸解氨酶活性、β-1,3 葡聚糖酶活性以及 WRKY、CaPR1 和 CaPTI1 基因的表达谱升高，这些基因是典型的盐胁迫和 PR 信号因子。此外，两种细菌菌株的接种都在初始接种期的正常条件下诱导了 PR 信号。然而，野生型水稻甲基杆菌 CBMB20 能够在盐胁迫下下调乙烯诱导的 PR 信号，并增强植物生长和耐盐性。总之，产 ACC 脱氨酶的内生细菌通过调节胁迫乙烯释放水平来下调植物中盐胁迫介导的 PR 信号，这为 ACC 脱氨酶产生内生细菌的有效定植和持久存在提供了一个新的范例，以实现更好的植物生长和生产力。
