| dc.description.abstract | Brazil is an essentially agricultural country, being highlighted in
citriculture worldwide, especially in the production and export of citrus in natura and concentrated juice.
Despite its economic relevance, the crops are severely affected by pests and pathogens, many of which
have few effective control measures. Huanglongbing (HLB), known as greening in some countries, is
considered the most serious and destructive disease of citrus, affecting growth, ripening, and fruit
morphology. The causal agents of HLB are phloem-limited bacteria of the species Candidatus
Liberibacter spp. that are transmitted by the Asian citrus psyllid, Diaphorina citri Kuwayama
(Hemiptera: Liviidae). As a consequence of HLB, the fruits are characterized by low juice content and
high acidity, which make their commercialization unfeasible and lead to serious economic losses.
Currently, HLB control is done by monitoring seedlings and using chemicals, but it is a laborious method
and not always effective, and may generate insect resistance. Thus, new technologies are needed, and
the development of plants overexpressing inhibitors of cysteine-peptidases (cystatins) is an interesting
alternative. Hemiptera use several proteases in their digestive process, mainly of the cysteine-peptidase
type and, therefore, the interaction between cystatins and cysteine-peptidases can affect the growth and
development of pest insects. Thus, this study aimed the heterologous expression of recombinant
cystatins from Citrus clementina (CclemCPI-1 and CclemCPI-3) and Citrus sinensis (CsinCPI-2) in
Escherichia coli and purification by affinity chromatography. These purified proteins were used to
evaluate the inhibitory activity in artificial diet for D. citri, at concentrations of 1 and 2 mg/mL, in order
to observe any effect on the psyllid development. In the tests performed in artificial diet containing the
3
purified proteins, a considerable mortality rate was observed for CclemCPI-1 protein, with 26.97% at 1
mg/mL and 48% at 2 mg/mL. In the assays with CclemCPI-3 and CsinCPI-2 proteins, mortality of 6
and 8%, respectively, was observed at the highest concentration. These data suggest a possible
interference in insect development. However, further tests will be necessary to standardize the results,
as well as to investigate the cystatin-peptidase interaction and evaluate for dose-dependence | |
