Identification of the sex-determining factor in the liverwort Marchantia polymorpha reveals unique evolution of sex chromosomes in a haploid system

半数体生物の性染色体上の性決定遺伝子を解明 --コケがもつ現生生物最古の起源の性染色体--. 京都大学プレスリリース. 2021-11-08.Sex determination is a central process for sexual reproduction and is often regulated by a sex determinant encoded on a sex chromosome. Rules that govern the evolution of sex chromosomes via specialization and degeneration following the evolution of a sex determinant have been well studied in diploid organisms. However, distinct predictions apply to sex chromosomes in organisms where sex is determined in the haploid phase of the life cycle: both sex chromosomes, female U and male V, are expected to maintain their gene functions, even though both are non-recombining. This is in contrast to the X-Y (or Z-W) asymmetry and Y (W) chromosome degeneration in XY (ZW) systems of diploids. Here, we provide evidence that sex chromosomes diverged early during the evolution of haploid liverworts and identify the sex determinant on the Marchantia polymorpha U chromosome. This gene, Feminizer, encodes a member of the plant-specific BASIC PENTACYSTEINE transcription factor family. It triggers female differentiation via regulation of the autosomal sex-determining locus of FEMALE GAMETOPHYTE MYB and SUPPRESSOR OF FEMINIZATION. Phylogenetic analyses of Feminizer and other sex chromosome genes indicate dimorphic sex chromosomes had already been established 430 mya in the ancestral liverwort. Feminizer also plays a role in reproductive induction that is shared with its gametolog on the V chromosome, suggesting an ancestral function, distinct from sex determination, was retained by the gametologs. This implies ancestral functions can be preserved after the acquisition of a sex determination mechanism during the evolution of a dominant haploid sex chromosome system

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“Romeo and Julietta” is the 25th novel of William Painter\u27s The Palace of Pleasure, Tome 2（1567）, and is one of the sources of William Shakespeare\u27s Romeo and Juliet（1595）. Painter\u27s “Romeo and Julietta” is a minor source compared to Arthur Brooke\u27s The Tragicall Historye of Romeus and Juliet（1562）, which Shakespeare mainly referred to, and therefore has not been paid much attention to so far. This essay first tries to evaluate Painter\u27s work as the second source of Shakespeare\u27s Romeo and Juliet by comparing it with Brooke\u27s and Shakespeare\u27s. Through the comparison of each work\u27s introduction of the story, handling of “Fortune”, characters of Romeo/Romeus and Juliet/Julietta, and the ending of the story, it is obvious how Shakespeare arranged his sources to make his dramatic version effective for the audience\u27s minds. It can also be seen that Shakespeare is not only under the influence of Brooke\u27s long poetic story, but also had the effects of Painter\u27s simple and compact story in mind. The latter part of this essay is a Japanese translation of Painter\u27s “Romeo and Julietta”, which will make it easier to compare Shakespeare\u27s two sources