Gene and expression analysis of the hexamerin family proteins from the grasshopper, Locusta migratoria (Orthoptera: Acridoidea)

Abstract

Hexamerins are large hemolymph-proteins that have been discovered in all insect species. According to the present study, hexamerins are not only storage proteins that provide amino acids and energy, but also transport hormones such as ecdysteroids. The hexamerin family genes cDNA from the grasshopper Locusta migratoria were cloned using RT-PCR and RACE methods. The biological functions of LmiHx5 were studied by RNA interference (RNAi), and qRT-PCR was performed to detect LmiHx transcripts after RNAi. Compared to the transcription database previously obtained, four family members (LmiHx1, LmiHx2, LmiHx4 and LmiHx5) of different LmiHx were determined. Homologous sequence alignments showed that the consistency of the amino acid sequence of LmiHx family members was 32%–43% and their encoded protein have the same three hemocyanin domains: hemocyanin-C, hemocyanin-N and hemocyanin-M. Gene expression patterns in different tissues and at different developmental stages showed that the LmiHx family genes are widely expressed in both female and male adults and at all developmental stages. The expression showed cyclical fluctuation with the nymphs molt. In addition, LmiHx2 mRNA expression level was the highest in fat body. LmiHx5 mRNA levels substantially decreased at 12, 24 and 48 h after dsLmiHx5 injection compared to the negative controls and almost not expressed at 96 h after dsRNA injection. The relative expression levels of other hexamerin family members showed varying degrees of increase after LmiHx5 RNAi. We speculate that hexamerin family gene members showed functional compensation.

Keywords

• Grasshopper
• hexamerin family genes
• cloning
• expression
• RNAi