Cloning and Expression of the EsxA Gene and Analysis of the Growth-Promoting Effects of the Encoded Protein on Rice Seedlings
Abstract An EsxA-encoding gene was previously identified in the genome of the plant growth-promoting rhizobacterium Paenibacillus terrae strain NK3-4. The EsxA gene was cloned and expressed in Pichia pastoris , after which the effects of the EsxA protein on rice seedling growth were analyzed to determine whether EsxA contributes to the plant growth-promoting activity of strain NK3-4. The EsxA gene was successfully cloned from the NK3-4 genome and ligated to the eukaryotic expression vector pPICZαA. The resulting pPICZαA- EsxA recombinant plasmid was inserted into P. pastoris cells, and EsxA gene expression in the yeast cells was confirmed. The treatment of seed- buds with the EsxA protein increased the root length by 1.35-times, but decreased the bud length. Additionally, in rice seedlings treated with EsxA, the root and shoot lengths increased by 2.6- and 1.7-times, respectively. These findings imply that EsxA is important for the promotion of rice plant growth by P. terrae strain NK3-4. Furthermore, the construction of the EsxA gene expression vector and the engineered strain may be useful for future investigations of the mechanism underlying the plant growth-promoting effects of EsxA, with implications for the application of EsxA for regulating plant growth.