Location: Emerging Pests and Pathogens Research
Project Number: 8062-22410-006-04-R
Project Type: Reimbursable Cooperative Agreement
Start Date: Oct 1, 2015
End Date: Sep 30, 2018
The objective is to enable growers to rapidly identify trees newly infected with Huanglongbing (HlB) by characterizing biomarkers that are predictive of infection before visual symptoms are observed on the tree. Early-infection HlB biomarkers will provide growers with critical information and allow them to rouge infected trees early to prevent the spread of infection within a grove. For California, early detection will help prevent a rapid spread of the disease. The second component of our work will enable us to develop precision inhibitors that block protein interactions critical for ACP survival and Clas transmission. Proof of concept is in hand for a protein interaction that is critical to regulate normal Clas growth.
Our goal is to leverage findings from our ongoing citrus research project on the discovery of plant peptide disease biomarkers, and the identification of protein interactions between the Asian citrus psyllid (ACP) and 'Candidatus Liberibacter asiaticus' (Clas), to provide citrus growers with novel control strategies for Huanglongbing (HlB; citrus greening). • HlB peptide biomarker discovery will build on findings from graft transmission analysis by characterizing citrus protein responses to Clas transmission by ACP feeding. • Using data on ACP and Clas proteins obtained from Protein Interaction Reporter (PIR) experiments, specific inhibitors will be designed and tested for the ability to block the activity of proteins necessary for Clas transmission. Additional protein interaction discovery will be pursued using alternate Clas enrichment strategies. Summary. We will continue development of citrus peptide biomarkers of HlB for early disease detection, using the ACP to inoculate citrus plants in growth chamber studies. We successfully implemented a protocol for Clas enrichment from ACP samples and identified interactions between ACP and Clas proteins, and are poised to design peptide inhibitors of these proteins and evaluate their suitability as vector control agents. • Mass spectrometry-based proteomics will be used to discover consistent changes in the abundance of specific peptides in citrus leaves in response to Clas transmission by the ACP for advanced early detection technology. • PIR technology has been used with Clas-enriched samples prepared from ACP to discover interactions between ACP and Clas proteins. • Interactions between Clas and the ACP during circulative transmission of the citrus greening pathogen within the insect vector represent high-value targets for specific and effective control of the spread of HlB. • We will exploit this highly refined structural data to design precision peptide inhibitors to specifically bind to proteins critical to pathogen transmission and block their activity. • Alternate Clas enrichment strategies will be used in tandem with PIR technology to identify additional protein interactions critical to Clas transmission. • Our current work has used adult psyllid samples as a starting material for Clas enrichment, and we will expand our scope to enrich Clas from nymph psyllid samples for parallel experiments on different developmental stages. • Clas is concentrated in the guts of ACP during disease transmission; the use of PIR to identify protein interactions in these tissues will illuminate specific events during the initial invasion of Clas into ACP cells. Expected Outcomes • Deliverable 1: Peptide biomarkers of HlB for detection of specific changes in citrus infected by Clas(+) ACP. • Deliverable 2: Precision peptide inhibitors designed to interfere with protein interactions within the ACP critical to Clas transmission, and structural details on additional protein targets for disease transmission control.