title: Evolution of Social Insect Polyphenism Facilitated by the Sex Differentiation Cascade.
abstract: The major transition to eusociality required the evolution of a switch to canalize development into either a reproductive or a helper, the nature of which is currently unknown. Following predictions from the 'theory of facilitated variation', we identify sex differentiation pathways as promising candidates because of their pre-adaptation to regulating development of complex phenotypes. We show that conserved core genes, including the juvenile hormone-sensitive master sex differentiation gene doublesex (dsx) and a krüppel homolog 2 (kr-h2) with putative regulatory function, exhibit both sex and morph-specific expression across life stages in the ant Cardiocondyla obscurior. We hypothesize that genes in the sex differentiation cascade evolved perception of alternative input signals for caste differentiation (i.e. environmental or genetic cues), and that their inherent switch-like and epistatic behavior facilitated signal transfer to downstream targets, thus allowing them to control differential development into morphological castes.
authors.affiliation: Institut für Zoologie, Universität Regensburg, Regensburg, Germany.
authors.forename: Antonia
authors.initials: A
authors.lastname: Klein
authors.affiliation: Centre of Excellence in Biological Interactions, Department of Biosciences, University of Helsinki, Helsinki, Finland.
authors.forename: Eva
authors.initials: E
authors.lastname: Schultner
authors.affiliation: Institut für Zoologie, Universität Regensburg, Regensburg, Germany.
authors.forename: Helena
authors.initials: H
authors.lastname: Lowak
authors.affiliation: Institut für Zoologie, Universität Regensburg, Regensburg, Germany.
authors.forename: Lukas
authors.initials: L
authors.lastname: Schrader
authors.affiliation: Institut für Zoologie, Universität Regensburg, Regensburg, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Heinze
authors.affiliation: Research School of Biology, Australian National University, Canberra, Australian Capital Territory, Australia.
authors.forename: Luke
authors.initials: L
authors.lastname: Holman
authors.affiliation: Institut für Zoologie, Universität Regensburg, Regensburg, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Oettler
mesh_terms: D000818:Animals; D001000:Ants / Q000235:genetics* / Q000502:physiology; D005075:Biological Evolution; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics; D029721:Drosophila Proteins / Q000096:biosynthesis / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D019476:Insect Proteins / Q000096:biosynthesis* / Q000235:genetics; D051741:Kruppel-Like Transcription Factors / Q000096:biosynthesis / Q000235:genetics; D010641:Phenotype; D012733:Sex Differentiation / Q000235:genetics*; D012919:Social Behavior
chemical_list: D004268:DNA-Binding Proteins; C070369:DSX protein, Drosophila; D029721:Drosophila Proteins; D019476:Insect Proteins; C497243:Kr-h2 protein, Drosophila; D051741:Kruppel-Like Transcription Factors