Differential expression of acetylcholinesterase 1 in response to various stress factors in honey bee workers

Sanghyeon Kim,Kyungmun Kim,Jae Ho Lee,Seung Hee Han,Si Hyeock Lee

doi:10.1038/s41598-019-46842-0

Abstract

The honey bee acetylcholinesterase 1 (AmAChE1) has been suggested to be related to stress response as judged from its elevated expression level under brood rearing-suppressed conditions. To further investigate the involvement of AmAChE1 expression in the stress response and its physiological functions, we analyzed altered expression profiles of AmAChE1 induced by diverse stress factors. In addition, transcription profiles of several heat shock protein (Hsp) genes (hsps) and the vitellogenin (Vg) gene (vg) known as general stress markers were investigated as positive references. Among the tested stress conditions, AmAChE1 expression was induced under the brood rearing-suppressed, crowding and heat shock conditions. The hsps, particularly hsp70 and hsp90, responded to seven of nine stress conditions tested, confirming that hsp expression profiles can serve as a general stress marker. Taken together, AmAChE1 expression is not suitable for using as a stress marker due to its limited response. Nevertheless, AmAChE1 expression appears to be connected, at least in part, to heat shock response and other pathways. Considering that AmAChE1 likely regulates the ACh titer particularly in non-neuronal tissues, thereby modulating the signal cascades mediated by mAChR, the AmAChE1 expression profile under different conditions likely provides important information on its physiological roles in honey bees.

Highlights

The western honey bee, Apis mellifera, plays a major role in the pollination of commercial crops and native plants[1]
Worker bees were treated with each stress factor and the protein expression levels of AmAChE1 were primarily evaluated and compared with those of control bees, along with transcription levels of AmAChE1 gene (Amace1) and several stress marker genes
In the quantitative real-time PCR results, the stress marker genes showed different expression patterns depending on tissues and age (Fig. 1B)

Summary

Introduction

The western honey bee, Apis mellifera, plays a major role in the pollination of commercial crops and native plants[1]. Some cellular stress responses such as the expression levels of heat shock proteins (Hsps) and cortico-releasing hormone-binding protein (CRH-BP) have been more recently used to evaluate stress in honey bees under a variety of stressors, including capture, transport, harnessing, cold, heat, and UV light[11]. It was reported that the pinewood nematode (Bursaphelenchus xylophilus) and fruit fly (Drosophila melanogaster) generate soluble AChE upon chemical stress[21,22] Taken together, these support the notion that AmAChE1 is likely an element of the stress regulation pathway in honey bees. To further investigate the involvement of AmAChE1 expression in the stress response and its physiological functions, we analyzed altered expression profiles of AmAChE1 induced by diverse factors, including chemicals (fluvalinate and neonicotinoid), temperature (heat and cold shock), UV-B irradiation, crowding, dehydration, starvation, Varroa mite infestation, bacterial challenge (Escherichia coli and Staphylococcus aureus) and brood-rearing suppression. The putative roles of AmAChE1 in stress regulation and other physiologies were further discussed

Methods

Results

Conclusion