Differentially expressed regulatory genes in honey bee caste development

Abstract

In the honey bee, an eminently fertile queen with up to 200 ovarioles per ovary monopolizes colony level reproduction. In contrast, worker bees have only few ovarioles and are essentially sterile. This phenotype divergence is a result of caste-specifically modulated juvenile hormone and ecdysteroid titers in larval development. In this study we employed a differential-display reverse transcription (DDRT)-PCR protocol to detect ecdysteroid-regulated gene expression during a critical phase of caste development. We identified a Ftz-F1 homolog and a Cut-like transcript. Ftz-F1 could be a putative element of the metamorphic ecdysone response cascade of bees, whereas Cut-like proteins are described as transcription factors involved in maintaining cellular differentiation states. The downregulation of both factors can be interpreted as steps in the metamorphic degradation of ovarioles in worker-bee ovaries.

Differential gene expression in queen–worker caste determination in bumble-bees

“…First, by investigating whether these genes are also differentially expressed between adult queens and workers and between reproductive and non-reproductive adult workers in B. terrestris, we tested whether the same genes underlie caste differences in larvae and adults. Second, by comparing the genes isolated in B. terrestris with those known to be associated with caste determination in A. mellifera larvae (Corona et al 1999;Evans & Wheeler 1999Hepperle & Hartfelder 2001), we tested whether the identity of relevant genes is conserved across these related taxa and whether any conserved genes share patterns of differential expression. Overall, we therefore sought to investigate whether, in the evolution of advanced sociality, genes that originally underlay reproductive differences between adults have been co-opted for use in caste determination during larval development.…”

A member of the short-chain dehydrogenase/reductase (SDR) superfamily is a target of the ecdysone response in honey bee (Apis mellifera) caste development

“…A detailed protocol for differential-display reverse-transcription PCR employed in the detection of ecdysone-responsive genes in the developing ovaries of last instar worker larvae of the honey bee (Apis mellifera L.) has previously been described (Hepperle and Hartfelder, 2001). In brief, ovaries were dissected from fifth-instar worker larvae and incubated for 3 h in honey beespecific medium in the presence or absence of makisterone A. RNA extracted from batches of 120 ovaries per experiment was used in permutational combinations of DDRT-PCR reactions (GeneExScreen primer kit, Biometra, Göttingen).…”

“…Sequences and putative regulatory properties of the transcription factors FTZ-F1-like and CUT-like have already been published (Hepperle and Hartfelder, 2001). A third honey bee EST, D5/U10-217, could be putatively assigned to the immunoglobulin superfamily of transmembrane proteins and growth factors (Tab.…”

“…Many of these exhibited sequence similarity with genes encoding metabolic enzymes and storage proteins, and for genes related to RNA processing and translation. It is interesting to note that no genes with regulatory functions were isolated in these screens, but were detected in a differential expression study on the response of larval ovaries to a caste-specific makisterone A pulse (Hepperle and Hartfelder, 2001). While providing insight into overall patterns of castespecific gene expression in vivo, such tissuespecific responses to metamorphic hormones were apparently diluted out in screens based on whole-body mRNA.…”

Screening of differentially expressed genes induced by water-soluble extracts from pollen during honeybee caste determination

“…This developmental switch depends not on genotypic differences but on the differential expression of entire suites of genes involved with larval fate (Jay et al, 2001). To date, the identity of differentially expressed genes associated with queenworker caste determination in larvae has been investigated in the honeybee, and groups of related genes have been identified (Evans et al, 2000;Hepperle et al, 2001;Piulachs et al, 2003;Guidugli et al, 2004;Grozinger et al, 2007). It is still not understood, however, how differential nutrition is linked to gene expression and how dietary changes alter pathways that modify the development of genetically identical female larvae.…”