Find in Library

Pieris brassicae L. is a serious pest of cultivated crucifers in several parts of theworld. Larvae of P. brassicae also feed prolifically on garden nasturtium (Tropaeolummajus L., of the family Tropaeolaceae). Proteolytic digestion was studied in larvaefeeding on multiple hosts. Fourth instars were collected from cauliflower fields beforetransfer onto detached, aerial tissues of selected host plants in the lab. Variable levels ofmidgut serine proteinases were detected in larvae fed on different hosts using proteinsubstrates (casein and recombinant RBCL cloned from cauliflower) and diagnostic,synthetic substrates. Qualitative changes in midgut trypsin activities and quantitativechanges in midgut chymotrypsin activities were implicated in physiological adaptation oflarvae transferred to T. majus. Midgut proteolytic activities were inhibited to differentextents by serine proteinase inhibitors, including putative trypsin inhibitors isolated fromherbivore-attacked and herbivore-free leaves of cauliflower (CfTI) and T. majus (TpTI).Transfer of larvae to T. majus significantly influenced feeding parameters but notnecessarily when transferred to different tissues of the same host. Results obtained arerelevant for devising sustainable pest management strategies, including transgenicapproaches using genes encoding plant protease inhibitors.