Major protease activity in the larval gut of Spodoptera litura boisd. (Lepidoptera: Noctuidae) is contributed by serine proteases

Sajitha R; Praveena M; Remya Patinhara Parambil; Alisha K S; Kannan Vadakkadath Meethal

Major protease activity in the larval gut of Spodoptera litura boisd. (Lepidoptera: Noctuidae) is contributed by serine proteases

Authors
Sajitha R, Praveena M, Remya Patinhara Parambil, Alisha K S, Kannan Vadakkadath Meethal

Abstract
Spodoptera litura or tobacco cut worm or army worm is a polyphagous pest and has a wide host range of up to 120 species. Insects use a variety of proteases for the digestion of food materials. Proper identification of the kind of protease present in the gut of the insect pest is important for targeting the gut proteases for the control of pests. In this study we identified the major proteases in the midgut of the larvae of S. litura using synthetic protease inhibitors. Phenyl Methane Sulphonyl Fluride (5mM) and Benzamidine Hydrochloride (10mM), the serine protease inhibitors, showed the highest protease inhibition of 68.12±1.42 and 60.25±0.79 % respectively. This indicates that serine proteases represent the major protease in the gut of the larvae of S.litura. Aspartyl protease inhibitor, pepstatin (7µM) and cysteine protease inhibitor, NEM (0.5mM) inhibits respectively 18.66 ±0.29% and 15.33 ± 1.74% of the gut protease activity of S.litura indicating that the contribution of aspartic protease and cysteine protease in protein digestion in the gut of S.litura is much less compared to serine proteases. In vivo feeding experiments with leaf dipped in PMSF followed by zymography of the gut extract revealed that the inhibitor is active under in vivo conditions. Further characterization of the major gut proteases in the midgut of the larvae of S. litura will help design strategies for the control of the pest targeting the gut proteases.

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