Tribolium castaneum zen paralogue function (Tc-zen1, Tc-zen2) and embryonic staged transcriptomes

"Unexpected mutual regulation underlies paralogue functional diversification and promotes epithelial tissue maturation in Tribolium". Insect Hox3/zen genes represent an evolutionary hotspot for changes in function and copy number. Single orthologues are required either for early specification or late morphogenesis of the extraembryonic tissues, which protect the embryo. The tandemly duplicated zen paralogues of the beetle Tribolium castaneum present a unique opportunity to investigate both functions in a single species. We dissect the paralogues' expression dynamics (transcript and protein) and transcriptional targets (RNA-seq after RNAi) throughout embryogenesis. We identify an unexpected role of Tc-Zen2 in repression of Tc-zen1, generating a negative feedback loop that promotes developmental progression. Tc-Zen2 regulation is dynamic, including within co-expressed multigene loci. We also show that extraembryonic development is the major event within the transcriptional landscape of late embryogenesis and provide a global molecular characterization of the extraembryonic serosal tissue. Altogether, we propose that paralogue mutual regulation arose progressively and drove multiple instances of zen subfunctionalization, leading to complementary extant roles. [RNA-seq data overview: PE 100 bp or PE 75 bp; 3-4 biological replicates/sample; for Tc-zen1 RNAi, Tc-zen2 RNAi, and age-matched wild type controls at the embryonic stages of peak expression and function: 6-10, 10-14, 48-52, and 52-56 hours after egg lay (hAEL) at 30 degrees Celsius; via parental RNAi (pupal injection) in the San Bernardino strain.]