Location: Emerging Pests and Pathogens Research
Project Number: 8062-22410-006-05-R
Project Type: Reimbursable Cooperative Agreement
Start Date: Oct 1, 2015
End Date: Sep 30, 2018
Objective. Our goal is to exploit the discoveries of proteins of the Asian citrus psyllid (ACP) and its bacterial endosymbionts which are involved in transmission of 'Candidatus Liberibacter asiaticus', the bacterial pathogen associated with Huanglongbing (HlB; citrus greening).
• We have initiated a research program aimed at understanding factors within the ACP which determine whether or not the insect can effectively transmit Clas, including factors related to host plant genotype, insect genotype and developmental stage, and proteins and metabolites produced by the ACP and its endosymbionts. • We will characterize the role of the polyketide toxin diaphorin, produced at high levels in the ACP by the endosymbiont 'Candidatus Profftella armatura', in the transmission of Clas. Summary. During our ongoing citrus research project, our team used mass spectrometry-based proteomics to characterize differences in protein expression between Clas(+) and Clas(-) populations of the ACP. These experiments have provided insight into metabolic and cellular changes in ACP which are harboring the citrus greening pathogen and suggest targets for development of vector control strategies. • Our continuing research will focus on functional characterization of several candidate ACP proteins relevant to Clas transmission. ACP genes encoding candidate proteins will be silenced using Citrus tristeza virus (CTV) technology to deliver gene silencing constructs through citrus plants, providing proof-of-concept for the effectiveness of blocking the spread of Clas by reducing production of insect proteins required for transmission. • A central finding of our ongoing citrus research project is the significance of the ACP endosymbiont Profftella in Clas transmission. Profftella proteins were disproportionately represented among the proteins discovered to be upregulated in Clas(+) insects, and these included proteins involved in the biosynthesis of the abundant polyketide diaphorin, a novel compound unique to Proffella and the ACP with cytotoxic properties. Continuing studies will be focused on characterizing the function of diaphorin in Clas transmission by the ACP, including identification of protein binding partners. • We have developed a panel of iso-female ACP lines and begun to characterize the Clas acquisition and transmission capacity of these genetically distinct populations. Characterization of these lines will continue as part of ongoing efforts to determine the genetic basis for vector competency. Expected Outcomes • Deliverable 1: Validated and functionally characterized protein targets within the ACP representing high-value candidates for the development of specific Clas vector control agents. • Deliverable 2: A panel of iso-female ACP lines characterized for their variation in Clas transmission and endosymbiont titer and distribution.