Immediate early genes Egr-1, Hr-38 and Kakusei function throughout the entire foraging period: An update study on honeybees

Honeybee foraging is a well-organized behavior that has been explored extensively. During foraging, bees search for food, taste quality, memorize the source, interact and communicate with other members of the colony, and collect food and stores it for the colony. This level of intelligence and typically well discipline behavior of these tiny insects can be easily observed during the foraging and thereby has attracted several researchers to uncover the mysterious behavior of honeybees and underlying regulatory mechanisms. Notably, a piece of study that interpreted honeybee dance language, a behavior used by honeybees used for communication among other members of the colony, during foraging, was Nobel prize winning research. However, only a little knowledge has been accumulated at the molecular and cellular levels toward understanding the mechanisms underlying of these sophistically regulated behaviors. Towards this approach, immediate early genes (IEGs) have been repeatedly shown to be promising tools in the cellular and molecular studies for understanding the regulatory mechanisms. Many studies have revealed that IEGs are genetic markers in honeybee brain functions and behaviors. Our recent studies have shown that three IEGs Egr-1, Hr38 and Kakusei have potential roles in honeybee foraging as well as learning and memory (Singh et al., 2018; Singh & Takhellambam, 2021; Singh et al., 2020). Further understanding, how long these genes remain upregulated during foraging, can reveal us the period of these genes’ participation during foraging. This piece of work is an extension of the earlier study to investigate whether gene expression continue to increase for longer time during the food reward foraging. Our study showed Egr-1 (09:00 - 14:00 hr./ 14:00 - 14:15 hr./ 14:15 - 14:30 hr./ 14:30 - 14:45 hr./ 14:45 -15:00 hr./ 15:00 - 15:15 hr./ 15:00 - 15:30 hr.: P=<0.0001) and Hr-38 (09:00 - 14:00 hr./ 14:15 - 14:30 hr./ 14:30 - 14:45 hr./ 14:45 - 15:00 hr.: p=<0.0001; 15:00 - 15:15 hr.: p=0.0003; 15:15 - 15:30 hr.: p=0.0008) expression continue to increase up to 15:30 hr., while Kakusei continue to increase up to 14:45 hr. (09:00 - 14:00 hr./ 14:00 - 14:15 hr./ 14:15 - 14:30 hr./ 14:30 - 14:45 hr./ 14:45 - 15:00 hr.: p=<0.0001), from the start of foraging or before foraging. The expression levels of all the three genes at 17:00 hr. is significantly higher than the 18:00 hr. (p=<0.0001) which is after foraging. We found that the gene expression level continued to remain upregulated throughout the entire 3 hours of foraging. This reveals that all the three genes Egr-1, Hr38, Kakusei, have a role to play from the beginning until the end of food reward foraging.