PDF(Pubmed)
Abstract：
Plant biostimulants have received attention as sustainable alternatives to chemical fertilizers. Extracellular polymeric substances (EPSs), among the compounds secreted by plant growth-promoting rhizobacteria (PGPRs), are assumed to alleviate abiotic stress. This study aims to investigate the effect of purified EPSs on rice under abiotic stress and analyze their mechanisms. A pot experiment was conducted to elucidate the effects of inoculating EPSs purified from PGPRs that increase biofilm production in the presence of sugar on rice growth in heat-stress conditions. Since all EPSs showed improvement in SPAD after the stress, Enterobacter ludwigii, which was not characterized as showing higher PGP bioactivities such as phytohormone production, nitrogen fixation, and phosphorus solubilization, was selected for further analysis. RNA extracted from the embryos of germinating seeds at 24 h post-treatment with EPSs or water was used for transcriptome analysis. The RNA-seq analysis revealed 215 differentially expressed genes (DEGs) identified in rice seeds, including 139 up-regulated and 76 down-regulated genes. A gene ontology (GO) enrichment analysis showed that the enriched GO terms are mainly associated with the ROS scavenging processes, detoxification pathways, and response to oxidative stress. For example, the expression of the gene encoding OsAAO5, which is known to function in detoxifying oxidative stress, was two times increased by EPS treatment. Moreover, EPS application improved SPAD and dry weights of shoot and root by 90%, 14%, and 27%, respectively, under drought stress and increased SPAD by 59% under salt stress. It indicates that bacterial EPSs improved plant growth under abiotic stresses. Based on our results, we consider that EPSs purified from Enterobacter ludwigii can be used to develop biostimulants for rice.
摘要：
植物生物刺激剂作为化学肥料的可持续替代品已经受到关注。细胞外聚合物质（EPS），在植物生长促进根际细菌（PGPRs）分泌的化合物中，被假定为减轻非生物胁迫。本研究旨在研究纯化EPS对非生物胁迫下水稻的影响，并分析其作用机制。进行了盆栽实验，以阐明在糖存在下接种从PGPR纯化的EPS对水稻生长的影响。由于所有EPS在应激后显示SPAD的改善，路德维吉肠杆菌,没有表现出更高的PGP生物活性，如植物激素的产生，固氮,和磷的溶解，选择进行进一步分析。在用EPS或水处理24小时后从发芽种子的胚提取的RNA用于转录组分析。RNA-seq分析显示，在水稻种子中鉴定出215个差异表达基因（DEG），包括139个上调基因和76个下调基因。基因本体论（GO）富集分析表明，富集的GO术语主要与ROS清除过程有关，解毒途径，和对氧化应激的反应。例如,编码OsAAO5的基因的表达，已知该基因在解毒氧化应激中起作用，EPS处理增加了两倍。此外，EPS的应用提高了SPAD和茎和根的干重90％，14%,27%,分别,在干旱胁迫下，盐胁迫下SPAD增加59%。这表明细菌EPS在非生物胁迫下改善了植物的生长。根据我们的结果,我们认为从路德维吉肠杆菌中纯化的EPSs可用于开发水稻生物刺激剂。
