Expression and activity of proteinases in the gut of stink bugs, Nezara viridula.

SARDOY, P; PAGANO, E.A.; ZAVALA J.A.

Rosario

Congreso; Reunión anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB); 2014

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

The southern green stink bug (SGSB) is a major pest of several crops world-wide, including Argentina. SGSB feeds on the seeds, reducing crop yield and seed quality. Although SGSB is well studied, little is known about their digestive physiology or how it overcomes soybean anti-herbivore defenses. Our study aimed to characterize the cysteine proteinases (CPs) responsible for digestive activity in the SGSB?s gut. Insects were fed either on artificial diet or soybean pods for 24-72h and then dissected. To clone the unknown genes, total mRNA was extracted and cDNA was obtained by RT-PCR, and degenerate primers were used for PCR amplification. Fragments were multiplied on E. coli after vector ligation (pGEM-T). Fragments were then sequenced using an ABI PRISM DNA Sequencer. Expression of sequences was analyzed by semi-quantitative PCR. In addition, CP activity was assayed with chromogenic substrates. Cathepsins L and B obtained had high similarity to reported bug sequences. Cathepsins L showed higher specific activity when compared to cathepsins B; activity and expression were not affected by diet. However, cathepsin B activity was reduced when insects fed on pods. Our results suggest that cathepsin B-like enzymes are inhibited by soybean proteinase inhibitors. This is the first step in identifying CPs in the gut of the SGSB and unveiling its complex digestive system.