Expression of midgut genes coding for peritrophic membrane (PM) proteins in the cabbage looper (Trichoplusia ni) in response to host plants and PM damage

The insect peritrophic membrane (PM) is a chitin/protein structure lining the midgut epithelium and playing important roles in physiological functions of the insect midgut. In Trichoplusia ni larvae, four PM proteins (IIM, CBP1, CBP2 and TnPM-P42) have been identified and their genes cloned. In order to understand the function of the PM proteins and regulation of PM formation, we analyzed the relative abundance of the transcripts of the four PM protein gens in the midgut of T. ni larvae by real-time quantitative PCR analysis and determined the expression of the PM protein genes in response to feeding on different host plants and to damage of the PM. The profiles of transcript levels of the four PM protein genes in larvae fed on different host plants indicated that PM protein gene expressions are regulated in response to host plants. The expression of the PM protein genes was up-regulated, in general, in T. ni larvae when PMs were disrupted. These results indicated that the expression of PM protein genes in insects is regulated in response to dietary factors to maintain the functional integrity of the PM structure.