Figure 1
From: Functional genetic characterization of salivary gland development in Aedes aegypti
Initiation of salivary gland development in Ae. aegypti and D. melanogaster differs. (A-I) CrebA protein expression marks the developing D. melanogaster salivary gland in lateral views of progressively older D. melanogaster embryos. Stages 9 (A) through 15 (I) are shown. (A) The D. melanogaster salivary gland initiates from two salivary gland placodes located in the VNE. (B-H) During development, cells from each individual placode invaginate forming internalized pairs of secretory tubes that elongate dorsally. (I) A ventral view of both glands in a Stage 15 embryo is shown. (J) In Ae. aegypti, expression of crebA mRNA transcript is not detected in VNE placodes. (K) Instead, salivary gland rudiments marked by crebA RNA expression (arrows, 55-h embryo) form adjacent to the proventriculus (white arrowhead). (L) By 57 h, secretory tubes (arrows) have formed. (M, N) These enlarge as development progresses. (O) Prominent thoracic structures located on either side of the proventriculus are evident at 75 h of development (arrows). (K-O) Dorsal views are shown. Embryos are oriented anterior-left in all panels.