Periplaneta americana midgut proteases differentially expressed against dietary components from different plant seeds

Abstract

Insect midgut proteases are known to be regulated by plant protease inhibitors. In the present study, the antinutritional effects of a variety of seed extracts against Periplaneta americana (Linnaeus) (Dictyoptera: Blattidae) midgut proteases are assessed in vitro and in vivo. Bioassays are conducted by allowing P. americana to feed on diets incorporated with the tested seed extracts. Low survival rates are recorded on a diet incorporated with seed powders of Ricinus communis (10%), Glycine max (30%), Datura alba (50%) and Mucuna pruriens (50%). Proteolytic and residual proteolytic activities are highly inhibited by the four seed extracts. Electrophoretic analysis shows that the majority of P. americana midgut protease isoforms are inhibited by the four seed extracts in vivo as well as in vitro. The midgut physiology of P. americana is affected by the seed extracts of D. alba, M. pruriens and Sapindus laurifolius, by over synthesising or changing mobilities of existing protease isoforms. Furthermore, some key proteases in P. americana midgut are involved in the regulation of other protease isoforms. These results suggest that seed extracts from the above plants are potential sources of plant protease inhibitors for managing economically important crop pests.