GENE RESPONSE TO STRESS IN THE ASIAN CITRUS PSYLLID (HEMIPTERA: PSYLLIDAE)

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. Knowledge of the molecular genetics of D. citri and other insects provides insights into the basic biology of insects. For example, insects can be subjected to stressful conditions and then screened to determine if the conditions promote specific genetic responses. Such information, by identifying critical genetic responses linked to survival, can then be used in the development of genetic tools and in novel management strategies aimed at reducing psyllids populations. In this study, transcriptional responses of D. citri adults against 3 stress factors were investigated: physical wounding, heat stress, and exposure to low doses of the insecticide imidacloprid. 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 degrees C, although 6 h of exposure to this temperature was lethal to psyllids. These results suggest that hsp70 may play a role in response to heat stress of D. citri. Summer temperatures can exceed 37 degrees 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.