Rhizobial volatiles: potential new players in the complex interkingdom signaling with legumes

Bacteria release a wide range of volatile compounds that play important roles in intermicrobial and interkingdom communication. Volatile metabolites emitted by rhizobacteria can promote plant growth and increase plant resistance to both biotic and abiotic stresses. Rhizobia establish beneficial nitrogen-fixing symbiosis with legume plants in a process starting with a chemical dialog in the rhizosphere involving various diffusible compounds. Despite being one of the most studied plant-interacting microorganisms, very little is known about volatile compounds produced by rhizobia and their biological/ecological role. Evidence indicates that plants can perceive and respond to volatiles emitted by rhizobia. In this perspective, we present recent data that open the possibility that rhizobial volatile compounds have a role in symbiotic interactions with legumes and discuss future directions that could shed light onto this area of investigation.This work was supported by grants from the Spanish Ministerio de Ciencia, Innovación y Universidades (MCIU), Agencia Estatal de Investigación (AEI) and European Regional Development Funds (FEDER; grant numbers PGC2018-096477-B-I00 and PGC2018-098372-B-I00), from Dirección General de Asuntos de Personal Académico-Universidad Nacional Autónoma de México (DGAPA/UNAM; PAPIIT IN200819), and the Consejo Nacional de Ciencia y Tecnología (CONACyT; 253549). We acknowledge funding by MCIU/AEI/FEDER, DGAPA/UNAM and CONACyT