Bacterial elicitation of transcriptional response of female squash bug, Anasa tristis (De Geer)

Authors: Shelby, Kent; Coudron, Thomas

Submitted to: Southwestern Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/5/2017
Publication Date: 3/1/2017
Citation: Shelby, K., Coudron, T.A. 2017. Bacterial elicitation of transcriptional response of female squash bug, Anasa tristis (De Geer). Southwestern Entomologist. https://doi.org/10.3958/059.042.0104.
DOI: https://doi.org/10.3958/059.042.0104

Interpretive Summary: Cucurbits are major horticultural cash crops in the United States. In 2011 cash revenue for squash and pumpkin totaled $396 million, plus $350 million for cantaloupe, and $543 million for watermelon. Squash bug feeding damages fruit and vines, reducing yield and consumer appeal. Squash bugs also transmit a bacterial infection, cucurbit yellow vine disease, between infected plants resulting in significant losses. Very few control measures such as insecticides, phytosanitary or bio-based methods provide effective controls for this pest, thus novel approaches are needed. We identified possible new squash bug control target genes within their immune and energy generating systems. Characterization of these new target squash bug genes shows that all are switched on by an infection. Among these was a key enzyme of energy metabolism. The data from this study will be useful primarily to the horticultural research community for the design of control measures based on suppression of gene expression. Additionally, integrated pest management professionals will use the database for more effective pest insect population monitoring, biological control, and resistance management.

Technical Abstract: The Squash bug, Anasa tristis (De Geer), is a major pest of squash, pumpkin, and other cucurbits throughout North America. A. tristis is a piercing/sucking feeder which causes extensive foliar wilting, fruit scarring, and in addition transmits plant pathogens. Current biological control agents available for control of A. tristis infestations are extremely limited in efficacy, thus newer control methods must be developed. Here we present studies of the immune system transcripts as the initial step in identifying potential vulnerable targets for control of gene expression. Following immune stimulation with bacteria the transcript levels of six components of the inducible innate system in adult female A. tristis were measured using quantitative PCR. An antibacterial peptide encoding transcript, anacin, an enzyme central to melanization, prophenoloxidase, and three sentinel proteins, scavenger receptor, ß-1,3, glucan binding protein, and peptidoglycan binding protein were all upregulated by bacterial elicitation. Additionally expression of a putative immunoregulatory cytokine, astakine, was identified. Expression of this cytokine was increased by septic puncture. Finally we found the novel up-regulation of an enzyme of central energy metabolism, arginine kinase, in response to a septic puncture of A. tristis adults.