Large scale transcript analysis of PI compensatory effects in the midgut and caeca of Locusta migratoria

Protease inhibitors (PIs) are among the most ubiquitous plant defences against herbivorous insects. These inhibitors arrest proteolytic digestion by binding to the proteases in the gut. However, many pest insects have coevolved mechanisms to counteract these effects. While the nature of these counter-defensive strategies has been well described for several insect pests, our understanding of how these responses are triggered and regulated remains limited. In this study we investigated the initiation of this adaptive response in the economically damaging migratory locust (Locusta migratoria), via microarray analysis of gut tissues following the dietary uptake of PIs. For this purpose, the total number of ESTs available for locusts was narrowed down to transcripts that were found expressed in gut and/or brain tissue. The remaining subset was used for the construction of an optimized microarray platform. Two condition experiment: locusts fed on control diet vs locusts fed on protease inhibitor-supplied diet (midgut samples), 3 biological repeats per condition. The overall experimental design consisted of an n+2 A-optimal design (n=6: 3 pooled midgut samples derived from control locusts - 3 pooled midgut samples derived from protease inhibitor-fed locusts)