Molecular characterization and expression of a heat shock protein gene (HSP90) from the carmine spider mite, Tetranychus cinnabarinus (Boisduval).

In this study, the cDNA of Tetranychus cinnabarinus (Boisduval) (Acarina: Tetranychidae) HSP90 (designated TcHSP90) was cloned using a combination of the homology cloning and rapid amplification of cDNA ends (RACE) approaches. The full-length cDNA of TcHSP90 is 2595 bp, including a 5'-untranslated region (UTR) of 177 bp, 3'-UTR of 249 bp, and an open reading frame (ORF) of 2169 bp. The ORF encodes a polypeptide of 722 amino acids with a predicted molecular weight of 83.45 kDa and a theoretical isoelectric point of 4.81. There is an mRNA polyadenylation signal of ATTAAA at the positions 2558-2564. In addition, the expression pattern of TcHSP90 mRNA relative to that of beta-actin gene in the three stains of T. cinnabarinus (AbR, abamectin-resistant strain; HR, heat-resistant strain; SS, the susceptible strain) were examined by using fluorescent real time quantitative PCR after the impact of abamectin, high and low temperature, respectively. The results showed that under the normal condition, the mRNA level of TcHSP90 was 1.64 and 1.29-fold higher in the AbR and HR than in SS, respectively. After 8 h treatment with abamectin, the TcHSP90 mRNA levels of SS, AbR, and HR were 1.25, 1.87, and 2.05-fold higher than those of their untreated controls, respectively. The TcHSP90 mRNA levels of SS, AbR, and HR were also significantly increased after being induced at 40 degrees C for 1 h, and they were 3.76, 3.42, and 3.79-fold higher than those of their untreated controls, respectively. The mRNA level of TcHSP90 was also significantly increased after being induced at 4 degrees C for 1 h. These results suggest that TcHSP90 might be involved in the abamectin and extreme temperature resistance or tolerance.

[Relative fitness of Tetranychus cinnabarinus resistant strains at different temperatures].

Based on resistance selection, the life tables of abameetin-resistant (AbR), fenpropathrin-resistant (FeR), and susceptible (S) strains of Tetranychus cinnabarinus at 15 degrees C, 20 degrees C, 25 C, 28 degrees C, 31 degrees C, 34 degrees C, and 36 degrees C were constructed, and the development duration, fertility, and intrinsic rate of increase (r(m)) of the strains were compared, aimed to understand the relative fitness of T. cinnabarinus resistant strains at different temperatures. The results indicated that compared with S strain, AbR and FeR strains had longer development duration at 15 degrees C but lower fertility at 20 degrees C-28 degrees C, and their relative fitness (represented by r(m)) was smaller at 15 degrees C but similar at 20 degrees C - 31 degrees C. For AbR and FeR strains, the fitness cost was moderate at 15 degrees C but lower at 20 degrees C - 31 degrees C. However, at high temperatures ( > or =34 degrees C), FeR strain possessed remarkable fitness cost while AbR strain showed better fitness.