Identification and comparative analysis of differential proteins expression in rice under biotic stress by protein sequencing

Rice ( Oryza sativa L .) plant is vulnerable to a number of pest and diseases. Among them sheath blight disease caused by Rhizoctonia solani , insect pest and brown plant hopper (BPH) ( Nilapavata lugens ) are the most devastating agents and major challenge to rice cultivation. Plant growth-promoting rhizobacteria (PGPR) are associated with plant roots which augment plant productivity and immunity. Protein analysis was carried out to study the molecular mechanisms underlying PGPR mediated pest and disease resistance and growth promotion. Plants were treated with and without Pseudomonas fluorescens strain Pf1 and challenged with pest and pathogen at 0, 6, 24, 48, 72, and 96 h after inoculation. The comparative analysis of relative abundances of protein bands between inoculated and non-inoculated samples was carried out. Five proteins were upregulated and 15 were differentially regulated in PGPR-primed plants challenged with BPH. In PGPR-primed plants challenged with pathogen, 27 proteins were upregulated. The differential protein bands were sequenced by Matrix Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry (MALDI-TOF-MS). Protein sequencing results showed high-percent homology with chloroplastic aldolase, fructose-bisphosphate aldolase, peroxidase, 2-cys peroxiredoxin bas1, chloroplastic-like, small subunit of ribulose-1,5-bisphosphate carboxylase, Os12g0291400 and hypothetical protein OsI_38046. Western blotting detected the presence of PR protein chitinase. The analysis confirmed the presence of chitinase of molecular weight 17, 20, and 35 kDa in PGPR primed plant challenged with R. solani. These results showed that the differentially expressed proteins possibly play role in biotic stress defense in plants challenged with biotic stress. Expression proteins remarkably influenced by Pf1 colonization, which might be a key element for induced systemic tolerance by PGPR.