A volatile organic compound analysis from Arthrobacter agilis identifies dimethylhexadecylamine, an amino-containing lipid modulating bacterial growth and Medicago sativa morphogenesis in vitro

Plant growth promoting rhizobacteria (PGPR) stimulate plant growth and development by different mechanisms, including the production of different classes of signaling molecules, which may directly affect plant morphogenesis. Here, we report the effects of inoculation of Arthrobacter agilis UMCV2, a PGPR isolated from the rhizosphere of maize plants on growth and development of Medicago sativa seedlings. A. agilis UMCV2 inoculation promoted growth in M. sativa plants as revealed by increased stem length, root length and plant biomass. Inoculation of A. agilis using divided Petri plates decreased taproot growth and increased lateral root formation in plants grown in separate compartments suggesting a role of volatile organic compounds (VOCs) produced by this bacterium in root development. The analysis of VOCs produced by A. agilis UMCV2 identified N,N-dimethyl-hexadecanamine (dimethylhexadecylamine), an amino lipid structurally related to bacterial quorum-sensing signals, which modulated A. agilis UMCV2 growth and plant development in a dose-dependent way. Taken together, our results indicate that bacterial VOCs can be perceived by legume plants to modulate growth and morphogenetic processes and identify a novel signaling molecule potentially involved in plant-rhizobacterial interactions.