Effects of Bacillus aryabhattai R60 on drought tolerance of maize based on transcriptome sequencing analysis

【Objective】In this study, the effects of Bacillus aryabhattai R60 strain on drought tolerance of maize under drought stress were analyzed, which provided theoretical reference for drought tolerant biologic fertilizer exploration and improvement of maize stress tolerance. 【Method】Transcriptome sequencing technology was used to analyze the changes in transcription levels of maize root inoculated with B.aryabhattai R60 strain under drought stress. Key differentially expressed genes(DEGs) in maize were explored, with sterilized distilled water injected into the root as the control, and GO function annotation and KEGG signaling pathway enrichment analysis were performed.【Result】There were 1524DEGs between the treatment group and the control group. Compared with control group, there were 421 up-regulated DEGs and 1103 down-regulated DEGs in the treatment group. The 421 up-regulated DEG swere annotated to 26 GO entries, including 13 entries of biological processes(cellular pathways, metabolic pathways, stimulus response, and biological regulation, etc), 3 entries of cell components(cellular structures, intracellular and protein complexes), and 10entries of molecular functions(binding, catalytic activities and transcriptional regulatory activities, etc). The top of 20DEGs with down-regulated expression were mainly annotated in 5 entries of biological processes(cellular pathways, biological regulation and stimulus response, etc), 2 entries of cell components(cell structures and intracellular), and 4entries of molecular functions(binding, transcriptional regulatory activities, etc). DEGs were mainly enriched in five signaling pathways of RNA transport, messenger mRNA pathway, plant hormone signal transduction, mitogen-activated protein kinase(MAPK) signaling pathway and plant-pathogen interaction. Compared with the control group, the expressions of key genes were down-regulated in the plant hormone signal transduction pathways of the treatment group, such as the negative regulation jasmonate ZIM domain-containing protein(JAZ) and downstream MYC2 family transcription factors in the jasmonic acid(JA) signaling pathway, the gibberellin(GA) receptor 1(GID1) and the negative regulation inhibitory protein(DELLA) in the GA signaling pathway, the protein phosphatase(PP2C) in the abscisic acid(ABA) signaling pathway, and the ethylene receptor transcription factor 1(ERF1) in ethylene signaling pathway, etc. In the MAPK signaling pathway, the genes expressions of MAP kinase substrate 1(MKS1) and mitogen-activated protein kinases(MPK3, MKK9 and MAPKKK18) were down-regulated. In addition, calmodulin protein(CALM) and calciumbinding protein(CML) genes expressions were down-regulated, while E3 ubiquitin-protein ligase(RHF, HOS1, and BRE1), ribose-phosphate pyrophosphokinase(PRPS), and UDP-glucuronate 4-epimerase(GAE4) encoded genes expressions were up-regulated. The results of real-time fluorescence quantitative PCR analysis were basically consistent with the transcriptome data.【Conclusion】The growth-promoting bacteria B. aryabhattai R60 may up-regulate the expressions of RHF, HOS1, BRE1, GAE4 and PRPS genes, and down-regulate the expressions of ERF1, DELLA and PP2C genes in the roots of maize plants, thereby activating multiple signal transduction pathways to enhance the tolerance of plants to drought stress.