Transcriptional Profiling of Midgut Immunity Figure 10. Apoptotic cells in the midgut. Midguts from larvae during the feeding (V-3: 12 h) and wandering (W: 6 h and W: 24 h) stages were sampled. Very few TUNEL-positive (red) cells were found in the midgut during the feeding stage (A, B). However, many cells were undergoing apoptosis in the midgut during the wandering stage (C, D, E, F). Before pupation (W: 24 h), old midguts were observed to slough off from the outer layer of basement membrane. DAPI was used for nuclei counter-staining. All images were merged from pictures taken using red and blue filters or using red and DIC (Nomarski) filters. Bars: 20 mm. doi:10.1371/journal.pone.0043769.g010 guts. Our qRT-PCR results indicate that genes belonging to the Imd pathway are up-regulated (Table S1; Fig. 8A and 8B). Many genes of the Toll pathway showed no obvious change (data not shown), possibly implying that the Toll pathway is incomplete to work. Thus, the Imd pathway might control AMP production in the midgut during the wandering stage. However, this conclusion still requires further study. After entering the wandering stage, the expressions of 113 genes associated with various aspects of metabolism and about 59 genes associated with transport of ions and other molecules were down- PLOS ONE | www.plosone.org 11 August 2012 | Volume 7 | Issue 8 | e43769