Understanding the molecular basis of plant growth promotional effect of Pseudomonas fluorescens on rice through protein profiling

Priming of P. fluorescens, 23 different proteins found to be differentially expressed in rice leaf sheaths and MS analysis revealed the differential expression of some important proteins namely putative p23 co-chaperone, Thioredoxin h- rice, Ribulose-bisphosphate carboxylase large chain precursor, Nucleotide diPhosphate kinase, Proteosome sub unit protein and putative glutathione S-transferase protein.Functional analyses of the differential proteins were reported to be directly or indirectly involved in growth promotion in plants. Thus, this study confirms the primary role of PGPR strain KH-1 in rice plant growth promotion.PGPR has promotional effect on plant growth and developmental processes in two different ways viz., 1) indirectly by decreasing or preventing some of the deleterious effects of a phytopathogenic organism; 2) directly by promoting plant growth through facilitating the uptake of nutrients from the environment [1]. Effect of PGPR on plant growth processes include, increase in germination rates, root growth, leaf area, chlorophyll content, magnesium, nitrogen and protein content, hydraulic activity, tolerance to drought and salt stress, shoot and root weights and delayed leaf senescence [2]. PGPR mediated plant growth enhancement was reported by many workers [3, 4, 1, 5, 6, 7 & 8]. Our previous reports also revealed the growth promotional activity of P. fluorescens in rice under laboratory, glass house and field conditions. However, there is no information available on the molecular basis of host plant - PGPR interaction in promoting plant growth.Among the various molecular biological techniques available, high throughput whole genome gene expression tools viz., microarrays and proteomics will allow us to have improved knowledge on the gene(s) and pathways induced during host-PGPR interaction. 2D-PAGE strategy has been widely used in understanding stress responses as well as in understanding constitutive differences between developmental stages or gen