Protecting tobacco plants from <scp>O<sub>3</sub></scp> injury by <i>Bacillus velezensis</i> with production of acetoin
Lidong Liu, Xiuyun Zhao, Yong Huang, Luxin Ke, Rui Wang, Gaofu Qi
Abstract
Plant growth‐promoting rhizobacteria (PGPRs) confer benefits to crops by producing volatile organic compounds (VOCs) to trigger induced systemic tolerance (IST). Here we show that Bacillus velezensis GJ11, a kind of PGPRs, produce VOCs such as 2,3‐butanediol and acetoin to trigger IST and cause stomatal closure against O 3 injury in tobacco plants. Compared to 2,3‐butanediol, acetoin was more effective on triggering IST against O 3 injury. The bdh ‐knockout strain GJ11Δ bdh with a blocked metabolic pathway from acetoin to 2,3‐butanediol produced more acetoin triggering stronger IST against O 3 injury than GJ11. Both acetoin and GJ11Δ bdh effectively enhance the antioxidant enzymes activity (e.g. superoxide dismutase and catalases) that is favorable for scavenging the reactive oxygen species like H 2 O 2 in leaves after exposure to O 3 . Consequently, less H 2 O 2 accumulation was observed, and reasonably less chlorophylls and proteins were damaged by H 2 O 2 in the tobacco leaves treated with acetoin or GJ11Δ bdh . The field experiment also showed that both acetoin and GJ11Δ bdh could protect tobacco plants from O 3 injury after application by root‐drench. This study provides new insights into the role of rhizobacterial B. velezensis and its volatile component of acetoin in triggering defense responses against stresses such as O 3 in plants.