Physiological, biochemical and proteomic insight into the response system of Streptomyces hygroscopicus OsiSh-2 to rice blast fungus toxins

Abstract

Magnaporthe oryzae is a major hazard to the growth and yield of rice and other graminaceous crops. The rice endophyte Streptomyces hygroscopicus OsiSh-2 has been reported to have a strong antagonistic effect on M. oryzae. However, the defence mechanism of OsiSh-2 against pathogens remains to be established. In this study, a combination of physiological, biochemical and label-free proteomics analyses were used to investigate the global response of OsiSh-2 to the toxins of M. oryzae (Mo-toxins). When exposed to Mo-toxins, OsiSh-2 regulated its growth rate to get rapid transition to the stationary growth phase where stronger antibiotic activity was achieved. Additionally, OsiSh-2 triggered reactive oxygen species (ROS) generation, hydrolase activity and biofilm formation in response to Mo-toxin stress. Finally, proteomic profiling confirmed that OsiSh-2 possesses the following sophisticated coping strategies against Mo-toxins: (1) sensing and transmittance of Mo-toxin signals by signal-transmitting proteins; (2) damaging the toxicity of M. oryzae by hydrolytic enzymes and other secondary products; and (3) guaranteeing the secretion and function of proteins by proteases and protein isomerases. Our research may promote the understanding of the interaction between antagonistic microbes and further broaden the scope of utilizing endophytic Streptomyces for biological control.