Spatial and temporal requirement of @entity72975 proventriculus activity during XXXX midgut development.

@entity920 @entity238 @entity72975
The @entity238 middle midgut cells derived from the endoderm develop into four distinct types of cell. Of these cells, @entity920 cells have invaginated microvillar membranes on their apical surface, and they are involved in two distinct functions, i.e., @entity920 absorption and acid secretion. The homeobox gene @entity72975 proventriculus (dve) is expressed in the midgut, and two transcripts, type A (   4.9kb) and type B (   3.5kb), have been identified. We isolated the deletion allele dve(E181) that completely removes the first exon for type-A (dve-A) transcript. Dve expression pattern in dve-A mutant background indicates that isoform switching is dynamically regulated in a cell-type specific manner. Using RNAi for dve-A, we examined spatial and temporal requirement of the Dve-A activity. Early Dve-A activity is required to repress isoform switching in @entity920 cells, and for establishment of two gut functions. Late Dve-A activity in @entity920 cells, but not in adjacent interstitial cells, is required for acid secretion, while the activity is redundantly required in both cells for the @entity920 absorptive function. Furthermore, ectopic type-B expression in larval @entity920 cells specifically impaired the @entity920 absorptive function. These results provide insight into molecular mechanisms to establish functional specificity.
