Characterization of a Chitin Synthase Encoding Gene and Effect of Diflubenzuron in Soybean Aphid, Aphis Glycines

Abstract

<p>Chitin synthases are critical enzymes for synthesis of chitin and thus for subsequent growth and development in insects. We identified the cDNA of chitin synthase gene (<i>CHS</i>) in <i>Aphis glycines</i>, the soybean aphid, which is a serious pest of soybean. The full-length cDNA of <i>CHS</i> in <i>A. glycines</i> (<i>AyCHS</i>) was 5802 bp long with an open reading frame of 4704 bp that encoded for a 1567 amino acid residues protein. The predicted AyCHS protein had a molecular mass of 180.05 kDa and its amino acid sequence contained all the signature motifs (EDR, QRRRW and TWGTR) of chitin synthases. The quantitative real-time PCR (qPCR) analysis revealed that <i>AyCHS</i> was expressed in all major tissues (gut, fat body and integument); however, it had the highest expression in integument (&#126;3.5 fold compared to gut). Interestingly, the expression of <i>AyCHS</i> in developing embryos was nearly 7 fold higher compared to adult integument, which probably is a reflection of embryonic molts in hemimetabolus insects. Expression analysis in different developmental stages of <i>A. glycines</i> revealed a consistent <i>AyCHS</i> expression in all stages. Further, through leaf dip bioassay, we tested the effect of diflubenzuron (DFB, Dimilin &#174;), a chitin-synthesis inhibitor, on <i>A. glycines</i>' survival, fecundity and body weight. When fed with soybean leaves previously dipped in 50 ppm DFB solution, <i>A. glycines</i> nymphs suffered significantly higher mortality compared to control. <i>A. glycines</i> nymphs feeding on diflubenzuron treated leaves showed a slightly enhanced expression (1.67 fold) of <i>AyCHS </i>compared to nymphs on untreated leaves. We discussed the potential applications of the current study to develop novel management strategies using chitin-synthesis inhibitors and using RNAi by knocking down <i>AyCHS </i>expression.</p