Effects of a protease inhibitor protein from Xenorhabdus bovienii on physiology of pea aphid (Acyrthosiphon pisum).

The effects of a protease inhibitor protein from Xenorhabdus bovienii strain xbi1 (Xbpi-1) on biochemistry and physiology of pea aphid (Acyrthosiphon pisum) were studied, and the effects of Xbpi-1 on the activities of aphid aminopeptidase and the concentrations of carbohydrates, free amino acids and lipids in A. pisum were determined. The results showed that the activity of aminopeptidase was reduced 18.30% by Xbpi-1 in vitro assays. In addition, the total sugar, glycogen, and lipid concentrations per aphid fed on an artificial diet with Xbpi-1 were reduced by 39.41%, 24.61% and 26.25%, respectively, compared to the controls. The total free amino acids in the aphids on the diet with Xbpi-1 was significantly decreased by 20.78% compared to the control. The mortalities of A. pisum were significantly higher when the concentrations of Xbpi-1 were 400 and 800 μg/ml in the artificial diet. The results from this study indicated that Xbpi-1 had adverse effects on the physiology and biochemistry of A. pisum.