Larval feeding status regulates the transcript levels of genes encoding PTTH and allatoregulatory peptides in silkworm Bombyx mori

In Bombyx mori,two dorsolateral neurosecretory cells(NSCs)in each of thetwo brain lobes have been identified as prothoracicotropic hormone(PTTH)producingcells.This neuropeptide in insects stimulates the prothoracic gland for the synthesis andrelease of ecdysone,responsible for the molting events.Allatotropin(AT)and allatostatin(AST)are allatoregulatory neuropeptides that regulate juvenile hormone biosynthesis.Here,by using RT-qPCR,we showed that in B.mori,nutritional stress modulates themRNA expression of AT and AST-C(allatostain type C)in the central nervous systemconsisting of the brain lobes and all the associated ganglia.Using whole-mount in situhybridization,we showed that the feeding status of Bombyx larvae also influences the ex-pression of PTTH in the NSCs of the brain.Food deprivation significantly decreased themRNA expression levels of PTTH in larvae at active or terminal growth period.Further,we showed that insulin modulates the expression level of PTTH.However,its action wasdependent on the feeding status of the larvae.At feeding,the insulin decreased the PTTHexpression level,while at food deprivation,the insulin increased the PTTH expressionlevel.The data thus indicates that larval feeding status plays an important role in alteringthe mRNA expression levels of allatoregulatory peptide genes and PTTH.