一株耐盐促生内生真菌Ophioceras leptosporum LW2的分离鉴定和耐盐特征分析

Isolation, identification, and salt tolerance characterization of a salt-tolerant and plant growth-promoting fungal strain Ophioceras leptosporum LW2

摘要:

目的 盐碱地严重危害土地健康，利用微生物改良盐碱地是一种绿色、有效的方式。内生真菌能够增强宿主植物应对生物和非生物胁迫的能力。因此，深入研究内生真菌的生物学特征，不仅可扩充内生真菌资源库，还能为绿色改良盐碱地和土壤修复提供优势菌种及有效策略。方法 采用平板胁迫培养法、扫描电镜观察以及多基因联合序列系统发育树分析研究菌种的特性；通过GFP荧光蛋白定位、台盼蓝染色法、扫描电镜观察及定殖曲线绘制，确定菌株在水稻根部的定殖情况；利用胁迫和非胁迫条件下的盆栽试验、过氧化物酶活性测定、转录组分析及基因表达量变化，探究菌株提升水稻耐盐性的机理。结果 获得了一株可提升寄主水稻耐盐性的内生真菌LW2。系统发育树分析显示其与Ophioceras leptosporum CBS 894.70处于同一最小分支，鉴定为Ophioceras leptosporum LW2。LW2菌株定殖于水稻根部，促进盆栽水稻的生长，与LW2共培养的水稻在鲜重、株高、茎宽上显著提升。盐胁迫下的水稻盆栽试验表明，LW2可以提升水稻的耐盐性能，显著提高盐胁迫下水稻的株高和茎宽，减轻盐胁迫引起的枯黄和萎蔫。耐盐性机理初探结果表明，LW2可通过影响水稻过氧化物酶含量促进活性氧清除，从而减轻盐胁迫对水稻的危害；同时，LW2还能调控乙烯信号通路中EIL1和HKTs基因的表达，通过乙烯信号途径影响离子转运，增强水稻的耐盐性。结论 本研究发现了一株可提升寄主水稻耐盐性的内生真菌菌株O. leptosporum LW2，并初步探究了其提升水稻耐盐性的机理，为微生物改良盐碱地与农业绿色发展提供了科学依据与优质菌株资源。

Abstract:

Objective Soil salinization is a serious threat to land health, and microbial remediation of saline-alkali soil is an eco-friendly and practical approach. Endophytic fungi can enhance host resistance to both biotic and abiotic stresses. Consequently, there is a need for further research on the biological characteristics of endophytic fungi. Such research can expand the existing endophytic fungal database and provide elite strains and effective strategies for the green remediation of saline-alkali soil and soil restoration.Methods The characteristics of the fungal strain were analyzed by plate culture under stress, scanning electron microscopy (SEM), and multi-gene phylogenetic analysis. The colonization of the strain in rice roots was examined by GFP fluorescence labeling, trypan blue staining, SEM, and colonization curve plotting. Pot experiments under stress and non-stress conditions, the peroxidase activity assay, transcriptome analysis, and gene expression analysis were carried out to decipher the mechanism by which the strain enhanced the salt tolerance of rice plants.Results An endophytic fungal strain, LW2, capable of enhancing the salt tolerance of host rice plants, was obtained. The phylogenetic tree showed that LW2 clustered with Ophioceras leptosporum CBS 894.70 in the same minimal clade, and thus the strain was identified as O. leptosporum LW2. LW2 successfully colonized rice roots and promoted the growth of potted rice. The rice plants co-cultured with LW2 showed significant increases in the fresh weight, plant height, and stem width. The pot experiments under salt stress showed that LW2 improved the salt tolerance of rice by increasing the plant height and stem width under stress conditions while alleviating stress-induced wilting and yellowing. LW2 mitigated salt-induced damage of rice by increasing the peroxidase activity and promoting reactive oxygen species (ROS) scavenging. In addition, LW2 regulated the expression of EIL1 and HKTs in the ethylene signaling pathway which affected ion transport, thereby enhancing rice salt tolerance.Conclusion This study identified an endophytic fungal strain, O. leptosporum LW2, capable of enhancing the salt tolerance of host rice. We preliminarily investigate the salt tolerance mechanism of this strain, providing scientific evidence and an elite strain for microbial remediation of saline-alkaline soil and the development of green agriculture.