Molecular cloning of heat shock protein gene HSP90 and effects of abamectin and double-stranded RNA on its expression in Panonychus citri (Trombidiformes: Tetranychidae)

Panonychus citri McGregor (Trombidiformes: Tetranychidae), the widely distributed citrus red mite, has developed resistance to most registered acaricides. Adaptation of arthropods to extreme environmental conditions has been related to increased expression of their heat shock proteins (HSPs). The objectives of this study were to explore the relationship between HSPs and resistance of Panonychus citri to the acaricide abamectin and the adaptation of Panonychus citri to high temperatures. The full-length cDNA of the HSP90 gene was cloned from an abamectin-sensitive strain of Panonychus citri. This gene consisted of 2,495 nucleotides with a complete open reading frame (ORF) of 2,169 nucleotides. This gene encoded a polypeptide of 721 amino acids with a predicted molecular weight of 83.44 kDa, a theoretical isoelectric point of 5.06, a 3' untranslated region (UTR) of 228 bp, and a 5' UTR of 98 bp. The results of real-time PCR analyses indicated that the expression of the HSP90 gene in P. citri was markedly affected by the concentration of abamectin, the duration of exposure to it and the temperature, suggesting that the up-regulation of the HSP90 gene may play an important role in abamectin resistance and adaptation to high temperatures in Panonychus citri. The results of RNA interference experiments indicated that the HSP90 gene from adult female Panonychus citri was sensitive to down-regulation by double-stranded RNA (0.1-0.2 mu g/mu L). This study provides a molecular basis for further analysis of the relationships between the HSP90 gene and the resistance of Panonychus citri to abamectin and to high temperatures.