Fig. 6

Models of the IIS-JH-Vg/YPs circuit showing the effect of a protein-enriched diet (without overfeeding) in (a) the solitary insect, D. melanogaster, and in (b) the termite C. secundus (current study), with key genes of the IIS pathway (including FOXO) depicted in the green and orange circles. Arrow: activation; stop bar: repression; dashed lines: potential re-wiring points; ?: connecting links unclear; red: up-regulation, blue: down-regulation, black: unaffected. In contrast to D. melanogaster, increased protein levels seem to lead to a downregulation of IIS in C. secundus, without effects on FOXO expression. Similarly, changes in IIS activity in the termite queen did not (strongly) impact JH biosynthesis (as indicated by the horizontal bar) unlike in D. melanogaster. Thus, fecundity is unaffected by protein enrichment in the termite, while it generally increases fecundity in solitary insects such as D. melanogaster. The negative linkage between IIS and longevity seems conserved as is the positive association between JH and fecundity, as reflected in the regulation of Vg and YP (the functional fly ‘equivalent’ of Vg) by JH. Figure (a) adapted from [61]