Microbial consortium mediated growth promotion and Arsenic reduction in Rice: An integrated transcriptome and proteome profiling

The adverse effects of arsenic (As) contamination are well known. Rice is a staple food for 50% of the world population but the accumulation of As into rice hampers the food security and safety. Thus the amelioration of As stress and reduction of As levels in rice are needed. In this study, transcriptome (Illumina sequencing) and proteome (2D gel electrophoresis) explored mechanisms of consortium (P. putida+C. vulgaris) mediated growth promotion and As amelioration in rice. The rice seedlings grown hydroponically in the Hewitt nutrient medium and after acclimatization, exposed to 50 mu M As alone as well as with microbial consortium to observe the impact at morphological and molecular level. The inoculation of microbial consortium significantly ameliorated the As toxicity, improved growth of root hairs and maintained cellular integrity of the epidermis, exodermis and the stele region during As exposure. Several genes showed differential expression in As and As+P. putida. Downregulation of As transporters (OsPIP2;2 and OsPIP2;3, OsTIP2;1) and higher expression of WRKY gene (WRKY28) during As+P. putida+C.vulgaris suggested reduction of As uptake in rice. The up-regulation of nutrient elements transporters (OsZIFL9, OsZIFL5, OsZIFL12 and OsZIP2, OsYSL15 and OsCOPT6) in the presence of consortium indicated the improved nutrient status of rice. Higher expression of regulatory elements like auxin/ indole 3 acetic acid (AUX/IAA), WRKY and myeloblastosis (MYB) TFs and down-regulation of defense responsive genes such Glutathione-S-transferase, Peroxidase and Glutaredoxinduring As+P. putida+C.vulgaris exposure was also observed. Proteome profiling demonstrated differential abundance of proteins involved in photosynthesis (chlorophyll a/b binding protein, photosystem I Fe-S centre), energy metabolism (ATP synthase subunit beta) transport, signaling (tubulin 1, actin 1), defense (glutathione S-transferase, phenylalanine ammonia lyase) and amino acid metabolism (cysteine synthase, glutamine synthetase), which supported the As ameliorative and growth-promoting potential of microbial consortium during As stress in rice plants. The study gives comprehensive information about gene and protein changes in rice plants in As+consortium exposure.