Potential roles of two Cathepsin genes, DcCath-L and DcCath-O in the innate immune response of Diaphorina citri

Abstract

Abstract Cathepsins belong to a group of mammalian papain-like cysteine proteases that play an important role in the insect immune response. In the present study, we identified two cathepsin genes from the Diaphorina citri genome database, cathepsin-L (DcCath-L) and cathepsin-O (DcCath-O). DcCath-L encodes a DcCath-L protein consisting of 348 amino acid residues, and DcCath-O encodes a DcCath-O protein consisting of 329 amino acid residues. DcCaths contain two conserved domains, the Inhibitor_I29 and Pept_C1 domains. Phylogenetic tree analysis revealed that DcCath-L and DcCath-O were divided into two different groups: Cathepsin-L and Cathepsin-O. Reverse transcription quantitative polymerase chain reaction analysis showed that both DcCath-O and DCCath-L were highly expressed in the midgut, while lower expression was observed in other tissues. Developmental stage expression analysis suggested that DcCath-O was mainly expressed in third instar nymph and adult, and DcCath-L was highly expressed in first and fourth instar nymph. Following exposure to two different heat-killed bacteria (Escherichia coli and Staphylococcus aureus) and Candidatus Liberibacter asiaticus, the expression of DcCath-O and DcCath-L was significantly increased and showed differential expression patterns at different time points. In addition, silencing of DcCath-L obvious affected the gene expression of members of the Toll pathway, while knock down of DcCath-L has no significantly influence. Overall, these data provide valuable information for further functional studies of D. citri cathepsins.