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Gene expression studies and molecular characterization of a cathepsin L-like from the Asian citrus psyllid Diaphorina citri, vector of Huanglongbing

Ferrara, Taise F.S., Schneider, Vanessa K., Lima, Patricia Silva, Bronze, Fellipe S., Machado, Marcelo F.M., Henrique-Silva, Flavio, Soares-Costa, Andrea, Carmona, Adriana K.
International journal of biological macromolecules 2020 v.158 pp. 375-383
Candidatus Liberibacter asiaticus, Citrus, Diaphorina citri, Escherichia coli, adults, cathepsin L, cystatins, cysteine, databases, digestive tract, eggs, embryogenesis, fruit diseases, gene overexpression, genes, greening disease, head, insect control, insect development, insects, nymphs, quantitative polymerase chain reaction, reverse transcriptase polymerase chain reaction, transcriptome, transgenic plants
Huanglongbing (HLB) is a devastating citrus disease associated with Candidatus Liberibacter asiaticus (CLas) and is transmitted by the psyllid Diaphorina citri Kuwayama. Diaphorina citri belongs to Hemiptera order, which has cysteine peptidases as the most abundant proteolytic enzymes present in digestive tract. As cysteine peptidases are involved in different insect development processes, this class of enzymes has acquired biotechnological importance. In this context, we identified a cathepsin L-like (DCcathL1) from the Diaphorina citri transcriptome database and expressed the enzyme in E. coli. Quantitative real-time RT-PCR was conducted to determine DCcathL1 gene expression in different parts and developmental phases of the insect. We observed that DCcathL1 expression in the gut was 2.59 and 2.87-fold higher than in the head and carcass, respectively. Furthermore, DCcathL1 expression was greater in eggs than in nymphs and adults, suggesting a putative role of the enzyme in the embryonic development. In addition, enzymatic inhibitory activity using four recombinant Citrus cystatins were performed. Among them, CsinCPI-2 was the strongest DCcathL1 inhibitor with a Kᵢ value of 0.005 nM. Our results may contribute in the development of strategies for D. citri control, such as silencing the DCcathL1 gene and the use of transgenic plants that overexpress peptidase inhibitors.