Stages of aestivation as a physiological state and the related biochemical composition in the grain chinch bug (Macchiademus diplopterus)

Authors: SMIT, RENATE - Stellenbosch University; Neven, Lisa; JOHNSON, SHELLEY - Stellenbosch University

Submitted to: Physiological Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/24/2023
Publication Date: 10/18/2023
Citation: Smit, R., Neven, L.G., Johnson, S.A. 2023. Stages of aestivation as a physiological state and the related biochemical composition in the grain chinch bug (Macchiademus diplopterus). Physiological Entomology. 49(1):1-13. https://doi.org/10.1111/phen.12420.
DOI: https://doi.org/10.1111/phen.12420

Interpretive Summary: The grain chinch bug is an endemic to the Western Cape in South Africa, and a pest of quarantine concern in pome and stone fruits. Researchers at the USDA-ARS laboratory in Wapato, WA and Stellenbosch University in South Africa collaborated to better understand the basic physiological and biochemical components of aestivation in this species. The focus of the investigation was to examine the influence of heat shock proteins and proteins involved in energy production and metabolism throughout the aestivation period. They found that there was a significant decrease in the number of individual proteins identified in samples before aestivation compared to early aestivation indicated the insects’ progression into a hypometabolic state. An increase in abundance of heat shock proteins occurred during the mid/mid-late aestivation period compared to the early period. This indicated the potential role of heat shock proteins in the insect’s ability to increase its thermo-tolerance at a later stage within the aestivation cycle. The results could provide insight into thermo-tolerance capabilities or mechanisms of the grain chinch bug. that could be exploited to develop postharvest quarantine treatments or disinfestation protocols.

Technical Abstract: The grain chinch bug (Macchiademus diplopterus Distant) is a critical phytosanitary pest, endemic to the Western Cape in South Africa. Once the insect has moved from its host wheat fields to the aestivation sites, which may potentially contain fruit orchards, where they display hitchhiker characteristics by seeking shelter . These areas could potentially contain fruit in orchards destined for export. Previous studies have indicated that the grain chinch bug has the ability to become more tolerant of thermal stresses as they progress through their aestivation cycle. To examine the potential physiological changes that occur during aestivation, molecular (soluble protein identification) and biochemical (macromolecules) analyses were performed on the insects before entering aestivation as well as early, mid, mid-late and late aestivation periods. These techniques provide useful information on the abundance and identity of individual soluble proteins and concentration of macromolecules, indicating whether compounds are up or down regulated throughout the aestivation cycle. The focus of this investigation was to examine the influence of heat shock proteins and proteins involved in energy production and metabolism throughout the aestivation period. Results could provide insight into thermo-tolerance capabilities or mechanisms of the grain chinch bug. The significant decrease in the number of individual proteins identified in samples before aestivation compared to early aestivation indicated the insects’ progression into a hypometabolic state. During the early, mid to mid-late aestivation period (Dec to May), large volumes of fruit are exported from South Africa. An increase in abundance of proteins, such as smHsp20, Hsp10, 70, 80 and 90, occurred during the mid/mid-late aestivation period compared to the early period. This indicated the potential role of heat shock proteins in the insect’s ability to increase its thermo-tolerance at a later stage within the aestivation cycle.