一株耐盐巨大普里斯特氏菌STPM1的鉴定及增强大麦耐盐性的功能验证

Identification and functional verification of a salt-tolerant Priestia megaterium strain STPM1 in enhancing salt tolerance of barley

摘要:

背景 土壤盐渍化是制约农业生产的主要非生物胁迫，利用根际有益微生物提升作物耐盐性，被视为一种有效且可持续的解决途径。目的 从盐地碱蓬(Suaeda salsa L.)根际土壤分离耐盐细菌，探究其对大麦耐盐性的影响及其生理与分子机制。方法 对源自盐碱地的菌株巨大普里斯特氏菌(Priestia megaterium) STPM1进行形态与分子鉴定，分析其耐盐碱能力及促生特性，并综合评价其在NaCl胁迫下对大麦种子萌发、幼苗生长、生理生化特性及盐胁迫响应基因表达的影响。结果 菌株STPM1被鉴定为巨大普里斯特氏菌(Priestia megaterium)，革兰氏阳性，具荚膜、产芽孢，可在12% NaCl及pH 5.0-9.0范围内生长。该菌具有固氮、溶磷和解钾能力，能分泌吲哚-3-乙酸(indole-3-acetic acid, IAA)与脱落酸(abscisic acid, ABA)等植物促生物质。盐胁迫下，接种菌株STPM1能显著提高大麦种子发芽率、促进幼苗生长，增强抗氧化酶系统活性，促进脯氨酸与ABA积累及调控盐胁迫响应基因的转录。结论 根际耐盐菌STPM1通过激活植物的抗氧化防御系统及ABA信号通路，显著增强大麦的耐盐性，在盐碱地微生物接种剂的开发中具有潜在应用价值。

Abstract:

Background Soil salinization is a major abiotic stress limiting agricultural production. Utilizing beneficial rhizosphere microorganisms to improve crop salt tolerance has been recognized as an effective and sustainable strategy.Objective To isolate salt-tolerant bacteria from the rhizosphere soil of Suaeda salsa L., investigate their effects on barley salt tolerance, and decipher the underlying physiological and molecular mechanisms.Methods A bacterial strain STPM1 (salt-tolerant Priestia megaterium 1) isolated from saline-alkali soil was identified through morphological characterization and molecular analysis. Its tolerance to salt and alkali, as well as its plant growth-promoting traits, were evaluated. The effects of STPM1 inoculation on barley under NaCl stress were comprehensively assessed in terms of seed germination, seedling growth, physiological and biochemical properties, and expression of salt stress-responsive genes.Results Strain STPM1 was identified as P. megaterium, a Gram-positive bacterium with capsule and capable of forming spores and growing in the media containing up to 12% NaCl and within the range of pH 5.0-9.0. The strain exhibited multiple plant growth-promoting traits, including nitrogen fixation, phosphate and potassium solubilization, and secretion of phytohormones such as indole-3-acetic acid (IAA) and abscisic acid (ABA). Under salt stress, inoculation with STPM1 significantly improved the seed germination, promoted seedling growth, enhanced antioxidant enzyme activities, increased the accumulation of proline and ABA, and regulated the transcriptional levels of several salt stress-responsive genes in barley.Conclusion The salt-tolerant rhizobacterium STPM1 enhances the salt tolerance of barley by activating the antioxidant defense system and the ABA signaling pathway, demonstrating the potential as a microbial inoculant for improving crop performance in saline-alkali soils.