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Title: Gene response to stress in the Asian citrus psyllid (Hemiptera: Psyllidae)

Author
item MARUTANI-HERT, MIZURI - Former ARS Employee
item Hunter, Wayne
item Hall, David

Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/28/2010
Publication Date: 12/8/2010
Citation: Marutani-Hert, M., Hunter, W.B., Hall, D.G. 2010. Gene response to stress in the Asian citrus psyllid (Hemiptera: Psyllidae). Florida Entomologist. 93:519-525.

Interpretive Summary: Gene expression by the Asian citrus psyllid, Diaphorina citri, under three stress factors were investigated: physical wounding, heat stress, and exposure to low doses of the insecticide imidacloprid. The psyllid is a vector of the plant-infecting bacterium Candidatus Liberibacter asiaticus, a pathogen which causes a disease known as huanglongbing, (citrus greening disease). Genetic studies provide insights into the genetic basis of psyllid biology. Identification of the critical genetic responses linked to survival can be used in the development of novel management strategies aimed at reducing psyllids populations, like Ribonucleic acid interference, RNAi. Of the six genes measured only heat stress showed an increased transcriptional activity of the heat-shock gene, hsp70, in adult psyllids exposed to 42°C. Exposure of six hours at this temperature was lethal to psyllids. These results suggest that hsp70 plays a critical role in surviving heat stress. Summer temperatures often exceed 37°C in Florida, Texas and California areas where the psyllids now occurs. Natural temperature fluctuations and gradual increases provide enough time for psyllids to acclimate to hot summer temperatures. We propose that the development of a method to disrupt gene expression, such as hsp70, may be applicable for future strategies to suppress psyllids populations.

Technical Abstract: Transcriptional responses of the Asian citrus psyllid, Diaphorina citri, under three stress factors were investigated: physical wounding, heat stress, and exposure to low doses of the insecticide imidacloprid. The Asian citrus psyllid, Diaphorina citri, is a vector of the phloem-inhabiting bacterium Candidatus Liberibacter asiaticus, a pathogen associated with the economically important citrus disease known as huanglongbing. Molecular genetics of D. citri provides insights into the basic biology of psyllid. Identification of these critical genetic responses are linked to survival which can then be used in the development of genetic tools and in novel management strategies aimed at reducing psyllids populations. No measureable transcriptional activity was observed for genes (cyp, gst, CuZn-SOD, hsc70, or hsp90), which, in other insects, have been shown to respond to either physical wounding, heat stress, or exposure to insecticides. However, increased transcriptional activity of a heat-shock gene, hsp70, was found in adult psyllids exposed to 42°C, and an exposure of six hours at this temperature was lethal to psyllids. These results suggest that hsp70 plays a role in response to heat stress of D. citri. Summer temperatures can exceed 37°C in Florida, Texas and California areas where the psyllids now occurs. Natural temperature fluctuations and gradual increases provide enough time for psyllids to acclimate to hot summer temperatures. We propose that the development of a method to disrupt gene expression, such as hsp70, may be applicable for future strategies to suppress psyllids populations.