Vitellogenin gene expression in stingless bee workers differing in egg-laying behavior

In stingless bee species, workers regularly lay eggs even in queenright colonies, but a variety of patterns ranging from a high frequency to a complete absence of laying workers has been recognized. We investigated whether these differences could be linked to alternative expression patterns of vitellogenin (Vg), the major component of egg yolk. In Frieseomelitta varia workers, which never lay eggs, and in Melipona scutellaris and Scaptotrigona postica that frequently participates in egglaying activity, we found discrepant developmental patterns of Vg transcript and of the corresponding protein. Interestingly, only in the permanently sterile F. varia workers, Vg protein was found to be constitutively present throughout pupal and adult stages. In workers as well as in males of this species, the quality of the alimentary diet shaped the levels of Vg transcript. In conjunct, our data suggest differences in the regulatory mechanisms underlying vg gene expression in these stingless bee species, and point to alternative roles for Vg, in addition to its essential function in vitellogenesis.