Figure 1

Model depicting the major findings from this study. In this study we have identified substantial differences in gene expression that can be detected as early as 6 hours after exposure to RJ. As indicated by the arrows, a small number of these genes maintain higher expression throughout larval development in either the queen caste (red arrow, mitochondrial cytochrome C, phosphoenolpyruvate carboxykinase (PEPCK), phytanoyl-CoA dioxygenase domain-containing protein 1 homolog and glycine N-methyltransferase-like (GNMT)) or worker caste (blue arrow, Bcl-2). The differences in gene expression occur earlier in larval development than previously reported [8, 15] and before the point at which we know larvae become committed to a particular caste [6]. These early, and sustained, differences in gene expression have led us to propose that this phase of early development represents a biased developmental trajectory. During this phase of early larval development gene expression is altered in response to RJ, biasing towards queen development (red line), or worker development (blue line) but not irreversibly so. Following this period, corresponding with peak JH levels in queens, we observe unique sets of genes induced in queen (red arrow, juvenile hormone-inducible (Jhl-26)) and worker castes (blue arrow, translocator protein, shep-like, lethal(2) essential for life and LOC10058039) that remain stably more highly expressed throughout the remainder of larval development. We propose that these changes in gene expression at 84 hours of larval development are associated with the induction of a committed developmental trajectory.