Root colonizing Burkholderia sp. AQ12 enhanced rice growth and upregulated tillering-responsive genes in rice

Association of 1-aminocyclo propane-1-carboxylate (ACC) deaminase producing bacteria with plants under abiotic stress conditions leads to stress alleviation not only by the regulation of ethylene concentration but also by the activation of numerous physiological and genetic mechanisms in plants. The objective of the current study was to evaluate the inoculation response of a plant-beneficial bacterial strain AQ12 on growth, physiological parameters, and expression of tiller responsive genes of rice plants grown under salt stress. The strain was identified as Burkholderia sp. based on 16S rRNA gene sequence analysis and it demonstrated promising ACC deaminase, indole-3-acetic acid (IAA) production, and phosphate solubilization traits in the presence of varying salt levels. The molecular confirmation of ACC deaminase activity was made by amplification and sequencing of the acdS gene. Inoculation of rice plants with the rifampicin-resistant derivative of Burkholderia sp. AQ12 resulted in a significant increase in length, dry matter, and cellular antioxidant enzyme levels together with the reduced levels of reactive oxygen species up to 50 mM salt stress. Furthermore, the inoculated plants revealed more than 2.0 fold increase in expression of the MOC1, OSH1, and OsTB1 genes up to 50 mM salt stress. It was concluded that inoculation of Burkholderia sp. AQ12 helped rice plants alleviate harmful salt stress effects by improving the growth, boosting the antioxidative defense system, and triggering the expression of tillering-responsive genes.