The oxygen concentration in cultures modulates protein expression and enzymatic antioxidant responses in Metarhizium lepidiotae conidia

Conidia from Metarhizium spp. are used for integrated pest control; however, environmental factors diminish the effectivity of these programs. Several approaches tried to improve conidia resistance to overcome this limitation, although little is known about the mechanisms involved in this effect. Here we measured the activity of antioxidant enzymes and conidia virulence, comparing the proteomic profiles of Metarhiziumlepidiotae CP-OAX conidia produced under normal (21% O2) and high oxygen atmospheres (pulses with 30% O2). We detected a higher virulence against Tenebrio molitor larvae, in addition to an increase in ultraviolet light tolerance in conidia produced under 30% O2, which correlates with increased glutathione reductase activity. Two-dimensional gel electrophoresis (2D SDS-PAGE) of proteins extracted in conidia harvested from both experimental conditions revealed a group of proteins that was observed only in conidia from oxidant atmospheres. Some of those proteins were directly involved in oxidative stress responses, whereas others were involved in conidial virulence, thermo-tolerance, and the central metabolism. Thus, a high atmospheric oxygen concentration (30%) activates antioxidant defence and general stress response mechanisms involved in conidia resistance to adverse environmental factors, which can ultimately translate into higher effectivity for the use of entomopathogenic fungi conidia in pest control.