Induction of microbe-mediated responsive proteomes by Methylobacterium oryzae CBMB20 on the salt-tolerant and salt-sensitive rice genotypes towards enhanced salt tolerance

Abstract Background Salt stress creates combinatorial stress conditions in the plants encompassing ion toxicity, physiological drought, nutritional imbalance, and oxidative stress. Severe salinity critically impacts both sensitive and tolerant rice genotypes. In addition, plants also recruit microbes establishing plant-microbe interactions leading to a complex array of microbe-mediated plant responses resulting to a cumulative overall enhancement of tolerance to salinity. The utilization of proteomics in the study of rice-microbe interactions expands our understanding of microbe-mediated responsive proteomes towards salt stress tolerance. Results Under severe salt stress, the proteomes of rice in terms of abundance and identity are mainly influenced by salt stress, rice genotypes, and Methylobacterium oryzae CBMB20 inoculation. Interestingly, the endophytic plant growth-promoting (PGP) M. oryzae CBMB20 mediated changes in the salt-stressed salt-sensitive IR29 resulting to similar proteomes to that of the salt-tolerant FL478. There are common upregulated and downregulated DAPs in both IR29 and FL478 due to salt stress indicating similar mechanisms of salt stress tolerance and similar biological and molecular processes severely affected by salt stress conditions. However, inoculation with M. oryzae CBMB20 resulted to shared significantly increased DAPs between the inoculated IR29 and FL478 indicating common mechanisms of microbe-mediated salt stress tolerance. In addition, there are genotype-specific DAPs with restored functions as a result of the application of M. oryzae CBMB20 in IR29 and FL478 indicating other key proteins essential for microbe-mediated salt stress tolerance. Conclusions Under severe salt stress conditions, there are common and genotype-specific proteomic changes in the salt-sensitive and the moderately salt-tolerant rice genotypes. However, the moderately salt-tolerant FL478 upregulated more proteins with higher fold change values indicating more efficient responses to salt stress. The bioinoculation with the versatile PGP M. oryzae CBMB20 onto the two contrasting rice genotypes mediated proteomic changes under salt stress conditions further enhancing stress responses in both rice genotypes.