Bacterial volatile organic compounds from Bacillus zanthoxyli HS-1 enhance tolerance responses against salt and high temperature in cucumber and cabbage

Abstract

Background Abiotic stresses pose significant challenges to agriculture and food security. Recent research has explored innovative approaches to enhance plant tolerance against such stresses, including the use of plant-derived compounds and plant growth-promoting rhizobacteria (PGPR). Despite this effort, identifying and characterizing PGPR as biostimulants for triggering plant tolerance response is still valuable. This study delves into how Bacillus zanthoxyli HS1 (BzaHS1) and BzaHS1-derived volatile organic compounds (VOCs) conferred systemic tolerance in cabbage and cucumber plants against salt and heat stresses. Results Both direct application of a BzaHS1 strain and indirect exposure to BzaHS1-derived VOCs promoted seedling growth of cabbage and cucumber plants under salt- and heat-stressed conditions. This induced systemic tolerance by BzaHS1 and BzaHS1-derived VOCs accompanied by increased callose deposition and narrow stomatal aperture against salt and heat stress, respectively. Reduced proline and malondialdehyde levels were observed in cabbage and cucumber plants treated with BzaHS1 and BzaHS1-derived VOCs, indicating that these plants were less sensitive to mock-treated plants. In addition, transcription of genes encoding superoxide dismutase, catalase, and heat shock protein 70 were increased in cabbage and cucumber plants treated with BzaHS1 and BzaHS1-VOCs. Conclusion Overall, BzaHS1 and its bVOCs show potential for enhancing salt and heat stress tolerance in plants through modulation of stress-responsive pathways involved in osmotic stress responses, regulatory processes, and antioxidant machinery.