Bacteria-derived diacetyl enhances Arabidopsis phosphate starvation responses partially through the DELLA-dependent gibberellin signaling pathway.

Plant growth-promoting rhizobacteria (PGPR) are naturally occurring soil microorganisms that colonize roots and stimulate plant growth. Some PGPR strains can directly regulate plant growth in the absence of physical contact with the plant, via volatile organic compounds (VOCs) emissions. Recently, we have described that respond differentially to diacetyl, a VOC from strain GB03 (GB03), through integral modulation of the immune system and the phosphate-starvation response (PSR) system, resulting in either mutualism or immunity. Under phosphate deficient conditions, diacetyl enhances salicylic acid- and jasmonic acid-mediated immunity and consequently causes plant hyper-sensitivity to phosphate deficiency. Here, we show that application of exogenous gibberellin (GA) partially alleviates the deleterious effect caused by either GB03 VOCs or diacetyl in under phosphate deficient conditions, while DELLA quadruple mutant exposed to GB03 VOCs exhibits a partial reduction on the stress symptoms. Moreover, diacetyl appears to enhance DELLA protein accumulation and increase the expression of several GA deactivation-related genes. These findings suggest that the DELLA-mediated GA signaling pathway is involved in the role of GB03 VOCs in regulating plant growth.