A 1,4-benzoquinone reductase of the entomopathogenic fungus Beauveria bassiana is involved in the degradation of Tribolium castaneum defensive secretions

N. PEDRINI; M. P. JUAREZ

Volos

Conferencia; International Conference of the IOBC/WPRS (OILB/SROP) Working Group on “Integrated Protection of Stored Products”.; 2011

International Organization for Biological Control

Tribolium castaneum, a major pest of stored and processed grains, is the most tolerant beetle to the entomopathogenic fungus Beauveria bassiana. T. castaneum use prothoracic and abdominal glands to produce defensive secretions, mostly composed by alkyl-1,4-benzoquinones (BQ). In this work, the antifungal properties of T. castaneum quinone-containing defensive secretions were investigated, in order to elucidate their role in the low susceptibility of T. castaneum to entomopathogenic fungi. In addition, a gene encoding for 1,4-benzoquinone reductase (bqr) was characterized in B. bassiana, and its function on BQ degradation is discussed. Reduced germination and a significant inhibition of B. bassiana growth were both detected when fungi were incubated in culture media containing dichloromethane-extracts of T. castaneum glands (0.3 to 0.6 insect equivalents/µl), and in the presence of synthetic BQ (4 to 25 µg/µl). A significant increment on benzoquinone reductase activity (2- to 3-fold, depending on the electron donor used) was measured in BQ-exposed fungi compared with controls. The cDNA of bqr consisted of 947 nucleotides and encoded a deduced protein containing 201 amino acids, with an estimated molecular mass of 21,4 kDa. Below minimal inhibitory concentration, bqr was significantly induced in BQ-exposed fungi (up to 40-fold expression, measured by qRT-PCR) varying with dose and exposition time. Although these results shed light on the interaction between entomopathogenic fungi and tenebrionid defensive secretions, additional studies on bqr gene would be needed to better understand the effect of these toxic compounds, in order to help develop a fungus-based biological control of T. castaneum.