Identification and initial characterization of novel neural immediate early genes possibly differentially contributing to foraging‐related learning and memory processes in the honeybee

Abstract

Despite possessing a limited number of neurones compared to vertebrates, honeybees show remarkable learning and memory performance, an example being 'dance communication'. In this phenomenon, foraging honeybees learn the location of a newly discovered food source and transmit the information to nestmates by symbolic abdomen vibrating behaviour, leading to navigation of nestmates to the new food source. As an initial step toward understanding the detailed molecular mechanisms underlying the sophisticated learning and memory performance of the honeybee, we focused on the neural immediate early genes (IEGs), which are specific genes quickly transcribed after neural activity without de novo protein synthesis. Although these have been reported to play an essential role in learning and memory processes in vertebrates, far fewer studies have been performed in insects in this regard. From RNA-sequencing analysis and subsequent assays, we identified three genes, Src homology 3 (SH3) domain binding kinase, family with sequence similarity 46 and GB47136, as novel neural IEGs in the honeybee. Foragers and/or orientating bees, which fly around their hives to memorize the positional information, showed induced expression of these IEGs in the mushroom body, a higher-order centre essential for learning and memory, indicating a possible role for the novel IEGs in foraging-related learning and memory processes in the honeybee.

Immediate-Early Promoter-Driven Transgenic Reporter System for Neuroethological Research in a Hemimetabolous Insect

“…2 , 1-5 , and 2-1 ). This is consistent with previous studies in other insect species ( Kiya et al, 2007 ; Ugajin et al, 2012 , 2016 , 2018 ; Fujita et al, 2013 ). These data indicate that, in general, mRNAs of insect neuronal IEGs show slower expression kinetics than those in the vertebrate systems.…”

“…Although the activity-regulated genes or neuronal IEGs have not been identified in any hemimetabolous insects including the cricket, recent genome-wide analyses of activity-regulated genes in vertebrates ( Nedivi et al, 1993 ; Matsuo et al, 2000 ; Wada et al, 2006 ; Spiegel et al, 2014 ) and several insect species ( Guan et al, 2005 ; Chen et al, 2016 ; Ugajin et al, 2018 ) highlighted evolutionarily conserved transcription factor IEGs. On the basis of previous reports, we selected four transcription factor genes as our candidates for activity-regulated genes in the cricket as follows: fos-related antigen ( fra ; c-fos homolog), jun-related antigen ( jra ; c-jun homolog), early growth response ( egr ; egr-1/zif268/NGFI-A homolog), and hormone receptor 38 ( hr38 ; NGFI-B/nur77/NR4A1 homolog).…”

Kenyon Cell Subtypes/Populations in the Honeybee Mushroom Bodies: Possible Function Based on Their Gene Expression Profiles, Differentiation, Possible Evolution, and Application of Genome Editing

“…Recent studies, however, reported that, in the silk moth and fruit fly, HR38 is an immediate early gene, whose neuronal expression is activated by neuronal excitation (Fujita et al, 2013 ), and that HR38 expression in the honeybee brain is induced by foraging behavior (Ugajin et al, 2018 ). These results suggest an alternative possibility that HR38 expression in the sKCs of the honeybee brain is a consequence of the foraging behavior, and does not necessarily represent a gene expression profile specific to the forager brain.…”

“…Since detection of neural activity using immediate early genes revealed that MB KCs (Singh et al, 2018 ; Ugajin et al, 2018 ), especially sKCs and some mKCs (Kaneko et al, 2013 ), are active in the brains of foragers, it is plausible that these KC subtypes are related to sensory information processing during the foraging flights.…”

Immediate early genes in social insects: a tool to identify brain regions involved in complex behaviors and molecular processes underlying neuroplasticity

“…Activation of IEGs or genes regulated by them were compared between different pupal and adult stages [89, 90], and between individuals performing different tasks like nursing the brood, dancing to communicate a novel food source to nestmates, and foraging for nectar or pollen [91, 92]. Behavioral approaches aiming to stimulate IEG expression in honey bees included more general stimulation like seizures induced by awakening from anesthesia [92–95], exposure to light [96] or plant and pheromonal odors [96–98], and sucrose feeding (food reward stimulation; [99]). In addition, more specific behaviors were correlated with IEG expression, for example, feeding of sucrose or pollen of different qualities [100], as well as different aspects of orientation flights [92, 95, 101] and foraging activity [102, 103].…”