Tissue-specific transcriptional patterns underlie seasonal phenotypes in
honey bees (Apis mellifera)
Abstract
Faced with adverse conditions, such as winter in temperate regions or
hot and dry conditions in tropical regions, many insect species enter a
state of diapause, a period of dormancy associated with a reduction or
arrest of physical activity, development, and reproduction. Changes in
common physiological pathways underlie diapause phenotypes in different
insect species. However, most transcriptomic studies of diapause have
not simultaneously evaluated and compared expression patterns in
different tissues. Honey bees (Apis mellifera) represent a unique model
system to study the mechanisms underpinning diapause. In winter, honey
bees exhibit a classic diapause phenotype, with reduced metabolic
activity, increased physiological nutritional resources, and altered
hormonal profiles. However, winter bees actively heat their colony by
vibrating their wing muscles; thus, this tissue is not quiescent. Here,
we evaluated the transcriptional profiles of flight muscle tissue and
fat body tissue (involved in nutrient storage, metabolism and immune
function) of winter bees. We also evaluated two behavioral phenotypes of
summer bees: nurses, which exhibit high nutritional stores and low
flight activity, and foragers, which exhibit low nutritional stores and
high flight activity. We found winter bees and nurses have similar fat
body transcriptional profiles compared to foragers, whereas winter bees
and foragers have similar flight muscle transcriptional profiles
compared to nurses. Additionally, differentially expressed genes were
enriched in diapause-related GO terms. Thus, honey bees exhibit
tissue-specific transcriptional profiles associated with diapause,
laying the groundwork for future studies evaluating the mechanisms,
evolution, and consequences of this tissue-specific regulation.