Transcriptional Signatures in Response to Wheat Germ Agglutinin and Starvation in Drosophila melanogaster Larval Midgut

One function of plant lectins is to serve as defenses against herbivorous insects. The midgut is the critical site affected by dietary lectins such as wheat germ agglutinin (WGA). We observed marked cellular structural and gene expression changes in Drosophila melanogaster third-instar larval midguts from insects WGA-fed or starved. Dietary WGA caused shortening, branching, swelling, distortion and in some cases disintegration of the midgut microvilli (Mv). Starvation was accompanied by shortening of the Mv. Microarray analyses revealed that dietary WGA evolved differential expression of 62 transcripts; seven of which were also differentially expressed in starved insects. The differentially regulated gene cluster in WGA-fed larvae were associated with (i) cytoskeletal organization, (ii) immune responses, (iii) detoxification reactions, and (iv) energy metabolism. Four putative transcription factor binding motifs (TFBMs) were associated with the differentially-expressed genes. At least one of these putative TFBMs exhibited substantial similarity to MyoD, a TFBM associated with cellular structures in mammals. These results are in keeping with the hypothesis that WGA causes a starvation-like effect as well as structural changes of midgut cells of Drosophila third-instar larvae.

9