Molecular and functional characterization of the ecdysone receptor isoform-A from the cotton mirid bug, Apolygus lucorum (Meyer-Dür)

• We isolated a 1.41 kb sequence encoding of ecdysone receptor isoform-A in Apolygus lucorum (AlEcR-A).
• Molecular size of the protein synthesized in vitro closely corresponded to the expected size of 59 kDa.
• AlEcR-A mRNA was detected at all developmental stages while high expression in epidermis and fat body.
• A loss of body weight, a delay of developmental and a high mortality were found after siRNA treatment.

We cloned the cDNA of the ecdysone receptor (EcR) isoform-A from the mirid bug, Apolygus lucorum (AlEcR-A). The AlEcR-A cDNA has an open reading frame of 1410 bp with a conserved sequence of approximately 20 amino acids at the carboxyl-end of its A/B-specific domain. Phylogenetic analysis showed that AlEcR-A is very similar to the EcR-A genes of other Hemiptera species. AlEcR-A mRNA was detected at all developmental stages of A. lucorum with peaks correlating to ecdysteroid pulses. AlEcR-A was also expressed in all analyzed tissues with maximum expression in the epidermis and fat body. An AlEcR-A mRNA of size 1.8 kb was detected in all tissues by northern blot analysis. We investigated the functions of AlEcR-A in A. lucorum growth and development using RNAi in vivo. Weights of fifth instar nymphs were significantly decreased in insects treated with AlEcR-A specific anti-sense RNA. Mortality from third instar nymphs to adults increased significantly along with a significant increase in instar duration.