Oral Annual Conference of the Genetics Society of Australasia with the NZ Society for Biochemistry & Molecular Biology

The genetic and mechanistic basis of worker sterility in the honey bee (737)

Isobel Ronai 1 , Benjamin P. Oldroyd 1 , Deborah A. Barton 1 , Vanina Vergoz 1
  1. The University of Sydney, Sydney, NSW, Australia

Worker sterility is a defining feature of social insects. To understand how worker sterility has evolved, it is important to identify both its genetic and mechanistic basis. We utilise an ‘evo-devo’ framework to propose that worker sterility can be conceptualised as ‘reproductive control points’ (specific mechanisms that reduce the reproductive capacity of workers). We provide empirical evidence for a control point in honey bee (Apis mellifera) workers: the environmental cue of the queen’s pheromone triggers the abortion of adult honey bee workers’ oocytes at mid-oogenesis. We show that when workers are exposed to the queen’s pheromone, their germ cells degenerate midway through development. Further, the degeneration of the germ cells has the morphological hallmarks of programmed cell death. We also find that the candidate gene, Anarchy, is the most promising gene identified so far for the mid-oogenesis control point in adult honey bee workers. Anarchy is associated with the termination of oogenesis and Anarchy’s expression is responsive to the presence of the queen in the colony. In addition, Anarchy’s transcripts localise to degenerating oocytes at the mid-oogenesis stage of development and when we knocked down the expression of Anarchy we found that this gene is associated with the programmed cell death pathway. We also establish that exposure to queen pheromone quantitatively increases programmed cell death activity (caspase activity) in the ovaries of workers. In summary, the mechanism underlying all the reproductive control points, and therefore worker sterility, is likely to be programmed cell death.