Impacts of temperature stress on gene expression of the insulin pathway in overwintering Megachile rotundata

Authors: CAMBRON, LIZZETTE - North Dakota State University; Yocum, George; GREENLEE, KENDRA - North Dakota State University

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/7/2019
Publication Date: 7/7/2019
Citation: Cambron, L.D., Yocum, G.D., Greenlee, K.J. 2019. Impacts of temperature stress on gene expression of the insulin pathway in overwintering Megachile rotundata [abstract]. Eighth International Symposium on Molecular Insect Science. July 7-10, 2019. Barcelona, Spain. Talk No. O16.

Interpretive Summary:

Technical Abstract: Diapause is a non-feeding stage that many insects go through to survive the winter months. Diapausing insects are exposed to environmental stressors including temperature stress but responding can be energetically costly. With fixed resources, overall metabolism and insulin signaling are maintained at low levels, but it is unclear if these change in response to temperature. This study focused on the impact of temperature on gene expression of the insulin pathway in overwintering alfalfa leafcutting bees, Megachile rotundata. Our hypothesis is that insulin signaling is responsible for allocating energy in response to temperature stress during overwintering. To test this hypothesis, M. rotundata were overwintered in either a lab setting at a constant 4°C or in the field in naturally fluctuating temperatures. Gene sequences were identified using a transcriptome dataset from a previous Illumina study. Expression levels of target genes in the insulin pathway were measured using quantitative PCR and normalized to reference genes. Expression levels of individual genes were analyzed by a two-way ANOVA, with time and location as factors. Principle components analysis (PCA) was performed to observe overall trends. We predicted that bees reared in the field would have more changes in gene expression throughout overwintering in response to naturally fluctuating temperatures. PCA showed that genes clustered not only by location but also by month, suggesting differences in gene expression patterns between bees in true diapause and those that are post-diapause quiescent. Our results showed that gene expression varied not as a whole pathway, but by individual genes instead. Bees overwintered in the field had more variation in individual genes compared to lab reared, suggesting the insulin pathway may be differentially regulated in response to temperature stress. Knowing how temperature impacts insulin signaling in overwintering bees can help researchers plan for climate-associated changes in pollinator health.