A local insulin reservoir ensures developmental progression in condition of nutrient shortage in Drosophila

Insulin/IGF signalling (IIS) controls many aspects of development and physiology. In Drosophila, a conserved family of insulin-like peptides (Ilp) is produced by brain neurosecretory cells and exerts systemic functions. Here, we describe the local uptake and storage of Ilps in the Corpora Cardiaca (CC), a group of alpha cell homolog that produces the glucagon-like hormone AKH. Dilp uptake relies on the expression of Impl2, an IGF-BP that accumulates in the CCs. During nutrient shortage, this specific reserve of Ilps is released and activates IIS in a paracrine manner in the prothoracic gland, securing accelerated entry into pupal development through the production of the steroid hormone ecdysone. We therefore uncover a sparing mechanism whereby local Ilp storage and release activates the production of steroids and ensures early developmental progression in adverse food conditions.

Peptidomic Analysis of the Brain and Corpora Cardiaca-Corpora Allata Complex in the Bombyx mori

The silkworm, Bombyx mori, is an important economic insect for silk production. However, many of the mature peptides relevant to its various life stages remain unknown. Using RP-HPLC, MALDI-TOF MS, and previously identified peptides from B. mori and other insects in the transcriptome database, we created peptide profiles showing a total of 6 ion masses that could be assigned to peptides in eggs, including one previously unidentified peptide. A further 49 peptides were assigned to larval brains. 17 new mature peptides were identified in isolated masses. 39 peptides were found in pupal brains with 8 unidentified peptides. 48 were found in adult brains with 12 unidentified peptides. These new unidentified peptides showed highly significant matches in all MS analysis. These matches were then searched against the National Center for Biotechnology Information (NCBI) database to provide new annotations for these mature peptides. In total, 59 mature peptides in 19 categories were found in the brains of silkworms at the larval, pupal, and adult stages. These results demonstrate that peptidomic variation across different developmental stages can be dramatic. Moreover, the corpora cardiaca-corpora allata (CC-CA) complex was examined during the fifth larval instar. A total of 41 ion masses were assigned to peptides.