Control of reproductive dominance by thethelytokygene in honeybees

Abstract

Differentiation into castes and reproductive division of labour are a characteristics of eusocial insects. Caste determination occurs at an early stage of larval development in social bees and is achieved via differential nutrition irrespective of the genotype. Workers are usually subordinate to the queen and altruistically refrain from reproduction. Workers of the Cape honeybee (Apis mellifera capensis) do not necessarily refrain from reproduction. They have the unique ability to produce female offspring parthenogenetically (thelytoky) and can develop into 'pseudoqueens'. Although these are morphologically workers, they develop a queen-like phenotype with respect to physiology and behaviour. Thelytoky is determined by a single gene (th) and we show that this gene also influences other traits related to the queen phenotype, including egg production and queen pheromone synthesis. Using 566 microsatellite markers, we mapped this gene to chromosome 13 and identified a candidate locus thelytoky, similar to grainy head (a transcription factor), which has been shown to be highly expressed in queens of eusocial insects. We therefore suggest that this gene is not only important for determining the pseudoqueen phenotype in A. m. capensis workers, but is also of general importance in regulating the gene cascades controlling reproduction and sterility in female social bees.

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

“…Some reports identified specific functional genes involved in caste development (Corona et al, 1999;Yamazaki et al, 2006;Lattorff et al, 2007;Aamodt 2008;de Azevedo et al, 2008). Others screened clusters of genes that belonged to distinctly different evolutionary and functional groups and pathways (Evans et al, 1999;Patel et al, 2007;Vieira et al, 2008).…”

Short-sighted evolution of virulence in parasitic honeybee workers (Apis mellifera capensis Esch.)

“…Moreover, the parasitic strain is unlikely to spread through sexual reproduction, because the highly virulent genotype depends on the thelytokous parthenogenesis of laying workers. Yet thelytoky is determined by homozygosity of the recessive th-allele (Lattorff et al 2007), and any sexual recombination with other alleles distorts this type of worker parthenogenesis. The specific highly virulent clonal parasitic genotype is maintained by the thelytokous parthenogenesis combined with a central fusion automixis and reduced recombination (Neumann and Moritz 2002).…”

Research strategies to improve honeybee health in Europe

“…This is greatly facilitated with the complete genome sequence for the honeybee at hand. For example the gene "thelytoky" (th) was mapped down to 20 cM within a few months and was recently identified as a transcription factor homologous to gemini in Drosophila (Lattorff et al, 2007). Two genes, th and csd (the sex locus), are currently the only two known honeybee specific genes.…”