Five Years of Access and Activism:
In April 2009, we marked the five year anniversary of PLoS Medicine's first call for papers with an editorial titled "A Medical Journal for the World's Health Priorities" [1]. The editorial was a renewed and revitalized call for papers, announcing a "refocusing of the journal's priorities." Going forward, we said, we would prioritize papers addressing those diseases with the greatest global burden. We would also aim to be as broad a journal as possible, publishing papers that explored not just biological causes of illness, but also social, environmental, and political determinants of health. Six months later, as we now mark the journal's official five-year anniversary (our launch issue was October 19, 2004), has our refocused scope had any impact on what we publish?
Male or Female? For Honeybees, a Single Gene Makes All the Difference:
Male or female? How genes send a developing embryo down one path or the other varies substantially among species. In honeybees, it boils down to whether a particular chromosomal location has the same version of a gene (called homozygous) or two different versions (heterozygous). Honeybees that have two different versions of the sex determination locus (SDL) develop female traits. Those that have two of the same version--or, more commonly, have only one version as a result of developing from an unfertilized egg--become male. This approach, known as complementary sex determination, is found in a number of social insects, yet is still poorly understood.
Sex Determination in Honeybees: Two Separate Mechanisms Induce and Maintain the Female Pathway:
Sexual differentiation is a fundamental process in the animal kingdom, and different species have evolved a bewildering diversity of mechanisms to generate the two sexes in the proper proportions. Sex determination in honeybees (Apis mellifera) provides an interesting and unusual system to study, as it is governed by heterozygosity of a single locus harbouring the complementary sex determiner gene (csd), in contrast to the well-studied sex chromosome system of Drosophila melanogaster. We show that the female sex determination pathway is exclusively induced by the csd gene in early embryogenesis. Later on and throughout development this inductive signal is maintained via a positive feedback loop of the feminizer (fem) gene, in which the Fem protein mediates its own synthesis. The findings reveal how the sex determination process in honeybees is realized by the regulation and function of two genes differing from Drosophila.
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