Species with separate sexes (dioecy) are a minority among flowering plants, but dioecy has evolved multiple times independently in their history. The sex‐determination system and sex‐linked genomic regions are currently identified in a limited number of dioecious plants only. Here, we study the sex‐determination system in a genus of dioecious plants that lack heteromorphic sex chromosomes and are not amenable to controlled breeding: Nepenthes pitcher plants. We genotyped wild populations of flowering males and females of three Nepenthes taxa using ddRAD‐seq and sequenced a male inflorescence transcriptome. We developed a statistical tool (privacy rarefaction) to distinguish true sex specificity from stochastic noise in read coverage of sequencing data from wild populations and identified male‐specific loci and XY‐patterned single nucleotide polymorphsims (SNPs) in all three Nepenthes taxa, suggesting the presence of homomorphic XY sex chromosomes. The male‐specific region of the Y chromosome showed little conservation among the three taxa, except for the essential pollen development gene DYT1 that was confirmed as male specific by PCR in additional Nepenthes taxa. Hence, dioecy and part of the male‐specific region of the Nepenthes Y‐chromosomes likely have a single evolutionary origin.

中文翻译：

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性别由雌雄异体猪笼草的放射状的XY染色体决定

在开花植物中，具有不同性别（雌雄异株）的物种很少，但雌雄异株在其历史上已经独立进化了多次。目前仅在数量有限的雌雄异株植物中鉴定出性别决定系统和与性别相关的基因组区域。在这里，我们研究了一种雌雄异株植物的性别决定系统，这些植物缺乏异型性染色体并且不适合控制繁殖：猪笼草。我们对三个猪笼草的开花雄性和雌性野生种群进行基因分型使用ddRAD-seq进行分类，并对雄性花序转录组测序。我们开发了一种统计工具（隐私稀有度），可从野生种群的测序数据的读取覆盖率中区分出真正的性别特异性和随机噪声，并在所有三个猪笼草类群中鉴定出了雄性特异性基因座和XY模式的单核苷酸多态性（SNP）。同态XY性染色体的存在。Y染色体的雄性特异性区域在这三个类群中几乎没有保留，除了必需的花粉发育基因DYT1被其他猪笼草类群中的PCR证实为雄性。因此，雌雄同体和猪笼草的男性特定区域的一部分 Y染色体可能具有单一的进化起源。