Asian Citrus Psyllid, Genetic Basis of Immunity

Authors: Hert, Mizuri; Hunter, Wayne; Shelby, Kent

Submitted to: International Research Conference on Huanglongbing
Publication Type: Proceedings
Publication Acceptance Date: 11/5/2008
Publication Date: 12/1/2008
Citation: Hert, M.M., Hunter, W.B., Shelby, K. 2008. Asian citrus psyllid, genetic basis of immunity. In: Proceedings of the International Research Conference on Huanglongbing. 6.9, p. 238-241, December 1-5, 2008, Orlando, Florida. Available: www.plantmanagementnetwork.org.

Interpretive Summary: We used a genomics approach to identify some of the genetic bases of immunity genes in the Asian citrus psyllid, identifying in particular genes associated with environmental and biological stresses. Only a few insecticides are being used to manage the Asian citrus psyllid (AsCP), Diaphorina citri (Hemiptera: Psyllidae), to reduce the spread of the phloem-inhabiting bacterium C. Liberibacter asiaticus, associated with huanglongbing (HLB) (also referred to as citrus greening disease). Imidacloprid is the most important systemic insecticide currently being used to control plant pests including psyllid, as either soil, seed or foliar treatments. Imidacloprid acts as an agonist at the nicotinic acetylcholine receptor and interferes with the transmission of stimuli in the insect nervous system. This blockage leads to the accumulation of acetylcholine, an important neurotransmitter, resulting in the insect’s paralysis and eventual death. In Drosophila melanogaster, the cytochrome P450 gene Cyp6g1 was shown to be capable of metabolizing Imidacloprid. Cytochrome P450 comprise a super family of enzymes that are involved in the biosynthesis of many biologically important compounds and metabolism of a variety of chemicals. Effective management of AsCP will be increased by advancing the understanding of the underlying genetic influences on AsCP responses to imidacloprid and other environmental stresses. In this study, we show psyllid immune gene responses against imidacloprid and other stress factors such as temperature to advance the understanding of insecticide resistance development and heat tolerance. All heat shock protein genes evaluated were induced by 1mL/3.84L admire treatment to citrus seedlings fed on by AsCP adults. This demonstrates some of the psyllid’s immune responses when stressed by pesticide and heat. Further experiments are under way to identify other genes which respond to biological and environmental stresses such as virus infection and cold. These insights provide genetic targets to effectively reducing the psyllid’s ability to respond, thus increasing AsCP susceptibility to low dosage insecticides and to Florida hot summer temperatures.

Technical Abstract: We used a genomics approach to identify some of the genetic bases of D. citri immunity, identifying in particular genes associated with environmental and biological stresses. Only a few insecticides are being used to manage the Asian citrus psyllid (AsCP), Diaphorina citri (Hemiptera: Psyllidae), to reduce the spread of the phloem-inhabiting bacterium C. Liberibacter asiaticus, associated with huanglongbing (HLB) (also referred to as citrus greening disease). Imidacloprid is the most important systemic insecticide currently being used to control plant pests including psyllid, as either soil, seed or foliar treatments. Imidacloprid acts as an agonist at the nicotinic acetylcholine receptor and interferes with the transmission of stimuli in the insect nervous system. This blockage leads to the accumulation of acetylcholine, an important neurotransmitter, resulting in the insect’s paralysis and eventual death. In Drosophila melanogaster, the cytochrome P450 gene Cyp6g1 was shown to be capable of metabolizing Imidacloprid. Cytochrome P450 comprise a super family of enzymes that are involved in the biosynthesis of many biologically important compounds and metabolism of a variety of chemicals. Effective management of AsCP will be increased by advancing the understanding of the underlying genetic influences on AsCP responses to imidacloprid and other environmental stresses. In this study, we show psyllid immune gene responses against imidacloprid and other stress factors such as temperature to advance the understanding of insecticide resistance development and heat tolerance. All heat shock protein genes evaluated were induced by 1mL/3.84L admire treatment to citrus seedlings fed on by AsCP adults. This demonstrates some of the psyllid’s immune responses when stressed by pesticide and heat. Further experiments are under way to identify other genes which respond to biological and environmental stresses such as virus infection and cold. These insights provide genetic targets to effectively reducing the psyllid’s ability to respond, thus increasing AsCP susceptibility to low dosage insecticides and to Florida hot summer temperatures.