Location: Emerging Pests and Pathogens Research
Project Number: 8062-22410-006-11-A
Project Type: Cooperative Agreement
Start Date: Sep 1, 2018
End Date: Aug 31, 2020
Citrus greening, also called Huanglongbing (HLB), is the most devastating disease of citrus and it is associated with plant infection by a Gram negative bacterium, “Candidatus Liberibacter asiaticus” (CLas). The bacterium itself is not harmful to humans but the disease has harmed citrus trees all around the world. Citrus greening disease is a threat to the survival of the U.S. citrus industry. Other than tree removal, there is no effective control once a tree is infected and there is no known cure for the disease. There is no resistance in any citrus species genotype screened to date. The bacterial pathogen that causes the disease is spread by Asian citrus pysllid, Diaphorina citri, a tiny sap-sucking insect. The insect vector harbors three bacterial endosymbionts and their effects on CLas transmission are not known. The objective of this research is to discover the contribution of the endosymbionts in the host’s biology and CLas transmission. This knowledge is important to understand the molecular interactions regulating CLas transmission by psyllids and to manipulate these interactions to block the spread of citrus greening disease.
Objective 1. To discover small RNA molecules that regulate CLas transmission. Question 1a. Do small RNAs play any role in the transmission of CLas by the Asian citrus psyllid? Hypothesis 1a. The pathogen and endosymbionts produce small RNAs which manipulate the physiology of the vector in a way that promotes CLas transmission from tree to tree. Hypothesis 1b. The profile of an insect’s small RNA changes after infection after acquisition of CLas in a tissue-specific manner due to an immune response to tree infection or acquisition and replication of the CLas bacterium in insect tissues. Objective 2. Identify D. citri genes that regulate CLas transmission Question 2a. Which D. citri genes are important for acquisition and transmission of CLas? Question 2b. Can we block the transmission by the pathogen by silencing of these genes? Hypothesis 2a. Some D. citri genes produce proteins or RNA which can be targeted by CLas. Hypothesis 2b. Silencing of the key genes will block CLas acquisition and transmission.