Gene expression profile affected by volatiles of new plant growth promoting rhizobacteria, Bacillus subtilis strain JS, in tobacco

Specific bacterial strains that promote plant growth have been investigated extensively and are characterized as plant growth-promoting rhizobacteria (PGPR). To identify the series of genes involved in PGPR-mediated enhanced plant growth, suppression subtractive hybridization was performed using cDNA from tobacco plants exposed to the PGPR strain, Bacillus subtilis strain JS. After hybridization, forward and reverse subtraction cDNA libraries containing 580 clones were obtained. Blastx search detected 170 single genes. These were classified into 14 functional categories, including metabolic processes and cellular processes implicated in growth promotion. Of the 36 responsive genes confirmed by RT-PCR, expression of 24 genes was up-regulated and 12 were down-regulated by treatment with B. subtilis JS volatile compounds. Photosynthesis pathway related genes encoding chlorophyll a/b binding protein, chloroplast sedoheptulose-1,7-bisphosphatase, and the photosynthate transport related gene were up-regulated, perhaps accounting for the volatile compound- mediated enhanced plant growth. Reactive oxygen species scavenging enzyme encoding genes as well as glutathione S-transferase and methionine-R-sulfoxide reductase were down-regulated.