Khila Abderrahman, Abouheif Ehab
Department of Biology, McGill University, 1205 Avenue Docteur Penfield, Montréal, QC, Canada H3A 1B1.
Proc Natl Acad Sci U S A. 2008 Nov 18;105(46):17884-9. doi: 10.1073/pnas.0807351105. Epub 2008 Nov 12.
A hallmark of eusociality in ants is the reproductive division of labor between queens and workers. Yet, nothing is known about the molecular mechanisms underlying reproduction in this group. We therefore compared the developmental genetic capacity of queens and workers to reproduce in several eusocially advanced species from the two largest subfamilies of ants, the Myrmicinae and Formicinae. In flies, the asymmetric localization of maternally encoded determinants (mRNAs and proteins) during oogenesis establishes oocyte polarity and subsequently ensures proper embryonic development. Vasa and nanos, two key maternal determinants, are properly localized in the posterior of queen oocytes, but their localization is impaired in those of the workers. This mislocalization leads to severe embryonic defects in worker progeny, and therefore, represents a constraint on worker reproduction that we call 'reproductive constraint.' We show that reproductive constraint is phylogenetically widespread, and is at high levels in most species tested. Reproductive constraint can simultaneously reduce or eliminate the workers' ability to produce viable eggs for reproduction, while preserving their ability to produce trophic eggs for nutrition, and thus, may have been the basis for the evolutionary retention of worker ovaries in the majority of ants. We propose that high levels of reproductive constraint has most likely evolved as a consequence of selection at the colony level to reduce or eliminate any potential conflict over worker reproduction, therefore maintaining harmony and colony efficiency in advanced ant societies.
蚂蚁真社会性的一个标志是蚁后和工蚁之间的生殖分工。然而，对于该群体中生殖背后的分子机制却一无所知。因此，我们比较了蚁后和工蚁在繁殖方面的发育遗传能力，这些蚁后和工蚁来自蚂蚁两个最大亚科（切叶蚁亚科和蚁亚科）中一些真社会性高度发达的物种。在果蝇中，卵子发生过程中母源编码决定因子（mRNA和蛋白质）的不对称定位确立了卵母细胞极性，进而确保胚胎正常发育。Vasa和nanos这两个关键的母源决定因子在蚁后卵母细胞的后部正确定位，但在工蚁的卵母细胞中其定位受损。这种定位错误导致工蚁后代出现严重的胚胎缺陷，因此，这代表了对工蚁繁殖的一种限制，我们称之为“生殖限制”。我们表明，生殖限制在系统发育上广泛存在，并且在大多数测试物种中处于高水平。生殖限制可以同时降低或消除工蚁产生用于繁殖的可存活卵的能力，同时保留它们产生用于营养的营养卵的能力，因此，这可能是大多数蚂蚁中工蚁卵巢在进化过程中得以保留的基础。我们提出，高水平的生殖限制很可能是由于群体层面的选择而进化而来的，目的是减少或消除工蚁繁殖方面的任何潜在冲突，从而在高度发达的蚂蚁社会中维持和谐与群体效率。
