GSE63993
Towards understanding the molecular basis of cockroach tergal gland morphogenesis. A transcriptomic approach
The tergal gland is a structure exclusive of adult male cockroaches that produces substances attractive to the female and facilitates mating. It is formed de novo in tergites 7 and 8 during the transition from the last nymphal instar to the adult. Thus, the tergal gland can afford a suitable case study to investigate the molecular basis of a morphogenetic process occurring during metamorphosis. Using Blattella germanica as model, we constructed transcriptomes from male tergites 7-8 in non-metamorphosing specimens, and from the same tergites in metamorphosing specimens. We performed a de novo assembly all available transcriptomes to construct a reference transcriptome and we identified transcripts by homology. Finally we mapped all reads into the reference transcriptome in order to perform analysis of differentially expressed genes and a GO-enrichment test. A total of 5,622 contigs appeared to be overrepresented in the transcriptome of metamorphosing specimens with respect to those specimens that did not metamorphose. Among these genes, there were six GO-terms with a p-value lower than 0.05 and among them GO: 0003676 (“nucleic acid binding”) was especially interesting since it included transcription factors (TFs). Examination of TF-Pfam-motifs revealed that the transcriptome of metamorphosing specimens contains the highest diversity of these motifs, with 29 different types (seven of them exclusively expressed in this stage) compared with that of non-metamorphosing specimens, which contained 24 motif types. Transcriptome comparisons suggest that TFs are important drivers of the process of tergal gland formation during metamorphosis. Overall design: We sequenced the mRNA from the tergites 7-8 (where the tergal gland appears in the male adult individuals) with Roche 454 GS Junior System, in 4 different developmental stages; in nymph 5 during the ecdysone peak when flat tergites are being produced; in nymph 6 day 1 when the adult program its being initiated; nymph 6 day 1 treated with Juvenil Hormone that inhibits the adult program; and in nymph 6 during the ecdysone peak when tergal gland its being formed. Different transcription factors were found to play a crucial role in TG morphogenesis.