Abstract: Cathepsin B plays an important role in insect metabolism. In this study, cathepsin B gene was cloned from mealybug Phenacoccus solenopsis and named as PsCb (GenBank accession no. JQ727999). This cDNA contains an open reading frame (ORF) which is 927 bp in length encoding 308 amino acids. Homology analysis shows that the N-terminal sequence of PsCB has larger variation, while the C-terminal sequence is conserved. Phylogenetic tree shows that PsCB is separated with other branches. Prokaryotic protein expression test showed the expressed product has the MW of 35 kDa, nearly equal to the predicted. Real-time PCR analysis revealed that PsCb mRNA was expressed in various developmental stages of P. solenopsis. The expression level was relatively lower at the egg stage, reached a peak at the 2nd instar nymph and then declined. Our study provides a theoretical basis for further study of the gene function, the development of cathepsin inhibitors as ovicides and inhibitors of embryonic development of P. solenopsis.

Key words: Phenacoccus solenopsis, cathepsin B, gene cloning, prokaryotic expression, gene expression profile