DUCTIN, A COMPONENT OF THE V-ATPASE, IS DEVELOPMENTALLY-REGULATED IN HELIOTHIS-VIRESCENS MIDGUT, AND ANTI-DUCTIN ANTIBODIES LABEL LATERAL MEMBRANES

We previously cloned from Heliothis virescens a 16-kDa protein that is homologous to other ductin sequences. We also reported its immunoloca lization with a specific affinity-purified anti-peptide antibody in th e midgut and Malpighian tubule of feeding larvae, and concluded that t he cloned proteolipid encodes the V-ATPase proton-transporting subunit c from the V-0 sector. We now present the immunolocalization of this protein in the midgut during the L-4-L-5 larval molt and early post-ec dysis into the fifth instar in H. virescens. The re suits show that th e spatial expression of the 16-kDa protein is developmentally regulate d. Labeling by anti-peptide antibody varies during the molt in the mid gut goblet cell apical plasma membrane and the goblet cell apical valv e. Epifluorescence and confocal microscopy revealed strong anti-ductin labeling in areas of cell-to-cell contact during the molt, and during early post-ecdysis into the fifth larval instar. The characteristic l abeling pattern observed in areas of cell-to-cell contact is consisten t with the claimed involvement of ductins in gap junctions. Conclusive evidence for the presence of the 16-kDa protein in areas of cell-to-c ell contact in the midgut of feeding larvae is, however, lacking. V-AT Pase regulation during the molt was also investigated by simultaneous immunohistochemistry with an anti-B subunit antiserum, a probe for the V-1 sector.