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To bee inside or outside? Impacts of overwintering environment on gene expression of the alfalfa leafcutting bee, Megachile rotundata
Author(s) -
Cambron Liz D.,
Yocum George D.,
Greenlee Kendra J.
Publication year - 2020
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2020.34.s1.07281
Subject(s) - overwintering , diapause , biology , gene , insulin receptor , gene expression , ecology , insulin , genetics , endocrinology , insulin resistance , larva
Diapause is a non‐feeding stage that many insects go through to survive the winter months. How nutrition is regulated during these months of overwintering is still unclear. 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 those pathways change in response to seasonal temperature fluctuations. Our hypothesis is that insulin signaling is responsible for allocating energy in response to fluctuations in temperature during overwintering months. To test this hypothesis, we overwintered alfalfa leafcutting bees, Megachile rotundata, in either a lab setting at a constant 4°C or in the field in naturally fluctuating temperatures, collected samples monthly throughout the winter, and then measured expression of genes in the insulin pathway using nCounter analysis (NanoString Technologies Inc.). nCounter is a highly multiplexed single molecule counting technique. A Dunn’s test was performed to analyze the effects of time and location for all possible comparisons. Our results showed that several genes were differentially expressed over time and between locations. However, more changes were seen in field samples, possibly in response to environmental cues. With a hierarchical cluster, field samples showed three distinct month clades, possibly correlating with different developmental stages: diapause, post‐diapause quiescence, and direct development. Although several genes were differentially expressed, many of them were downstream of the insulin pathway (Foxo, MAPK, GSK3β). This could mean that components of the insulin pathway are being utilized to respond to temperature fluctuations in the field. Along with evidence from other studies, our results suggest that insects may use different mechanisms for diapause regulation in response to their environment. This plasticity in regulation may be achieved by using targets of other pathways such as that of the insulin pathway. There is no denying that pollinators are crucial for the health of our ecosystem, but before we can save the bees, we need a better understanding of how their overall physiology is impacted in a drastically changing environment. Support or Funding Information This research was funded, in part, by grants from the National Science Foundation Graduate Research Fellowship and an NSF Graduate Research Internship with the USDA‐ARS Fargo, ND, and NSF EPSCoR‐1826834 to KJG.