Role of ecdysteroids and juvenile hormone in regulation of larval haemolymph protein gene expression in Galleria mellonella

Abstract

Developmental pattern of expression of two fat body specific genes in Galleria mellonella was determined by dot hybridization of total RNA extracted from diverse developmental stages. These studies using cDNA clones, pLhp76 and pLhp82, as pi bes showed that Lhp76 transcripts were produced all through the larval life, while Lhp82 transcripts were produced only in the last larval instar. Pupae and adults did not produce either transcript. Although penultimate-instar larvae do not normally produce Lhp82 transcripts, they do produce these transcripts, as determined by Northern analysis, following prothorax ligation. Similarly, activation of both these genes during the last larval stadium can occur in neck- or prothorax-ligated day-0 larvae. However, application of juvenile hormone blocked production of Lhp82 transcripts in prothorax-ligated or neck-ligated day-0 last instar larvae and partially blocked in prothorax-ligated penultimate instar larvae. These observations suggest that activation of the last-instar specific Lhp82 gene depends on the absence of juvenile hormone and is independent of ecdysteroid-mediated reprogramming of the genome.