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Myoglianin triggers the premetamorphosis stage in hemimetabolan insects
Author(s) -
Kamsoi Orathai,
Belles Xavier
Publication year - 2019
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fj.201801511r
Subject(s) - juvenile hormone , prothoracic gland , ecdysone , corpus allatum , cockroach , metamorphosis , biology , medicine , endocrinology , ecdysone receptor , farnesol , instar , microbiology and biotechnology , hormone , gene , larva , biochemistry , botany , transcription factor , nuclear receptor , ecology
Insect metamorphosis is triggered by a decrease in juvenile hormone (JH) in the final juvenile instar. What induces this decrease is therefore a relevant question. Working with the cockroach Blattella germanica , we found that myoglianin (Myo), a ligand in the TGF‐β signaling pathway, is highly expressed in the corpora allata (CA, the JH‐producing glands) and the prothoracic gland [(PG), which produce ecdysone] during the penultimate (fifth) nymphal instar (N5). In the CA, high Myo levels during N5 repress the expression of juvenile hormone acid methyl transferase, a JH biosynthesis gene. In the PG, decreasing JH levels trigger gland degeneration, regulated by the factors Krüppel homolog 1, FTZ‐F1, E93, and inhibitor of apoptosis‐1. Also in the PG, a peak of myo expression in N5 indirectly stimulates the expression of ecdysone biosynthesis genes, such as neverland, enhancing the production of the metamorphic ecdysone pulse in N6. The Myo expression peak in N5 also represses cell proliferation, which can enhance ecdysone production. The data indicate that Myo triggers the premetamorphic nymphal instar in B. germanica and possibly in other hemimetabolan insects.—Kamsoi, O., Belles, X. Myoglianin triggers the premetamorphosis stage in hemimetabolan insects. FASEB J. 33, 3659–3669 (2019). www.fasebj.org