Biochemical and Hsp70 gene expression changes in Apis mellifera workers following water and food deprivation

Resource scarcity poses a real challenge to living organisms. The present study aimed to understand the implications of water and food lack on some biochemical markers. The study also aimed to investigate the expression of Hsp70 gene under the same stress conditions. The Hsp70 gene maintains cellular proteostasis. It is unique in its high sensitivity and rapid response to various stress factors compared to other Hsps.

Brood frames of Carniolan hybrid bees were incubated at 30 °C and 70% RH. Emerged bees were placed in plastic cages (30 individuals per cage) and received daily diets of pollen-sugar pastes and sugar solutions. After nine days, bees were independently subjected to dehydration and starvation experiments for 24 h. One group was deprived of only sugar solutions (Dehydrated DH), another group was denied both sugar solutions and pollen pastes, receiving only tap water (Starved ST), while a third group continued without water or food deprivation (Control C). Bee samples were collected at 12-hour intervals in each experiment for subsequent investigations. Biochemical measurements were performed on total protein, total antioxidant capacity, peroxidase, catalase, glutathione S-transferase, and acid phosphatase. Gene expression of Hsp70 gene was under observation. Bee weights were also considered.

Both dehydrated and starved bees showed notable changes in their examined biomarkers. Starvation had a more pronounced and rapid biochemical effect. The decreases in Hsp70 mRNA levels following water or food deprivation were surprising to us and reflect the severity of these two stressors. Other differences were also recorded in the weights of dehydrated and starved bees.

This study reveals honeybees' extreme sensitivity to nutritional stress and warns against depriving them of water or food for even a few hours.