Parthenogenetic species of Caucasian rock lizards of the genus Darevksia are important evidence for reticulate evolution and speciation by hybridization in vertebrates. Female‐only lineages formed through interspecific hybridization have been discovered in many groups. Nevertheless, critical mechanisms of oogenesis and specifics of meiosis that provide long‐term stability of parthenogenetic species are still unknown. Here we report cytogenetic characteristics of somatic karyotypes and meiotic prophase I nuclei in the diploid parthenogenetic species Darevskia unisexualis from the new population “Keti” in Armenia which contains an odd number of chromosomes 2n = 37, instead of the usual 2n = 38. We revealed 36 acrocentric chromosomes and a single metacentric autosomal chromosome, resulting from Robertsonian translocation. Comparative genomic hybridization revealed that chromosome fusion occurred between two chromosomes inherited from the maternal species, similar to another parthenogenetic species D. rostombekowi. To trace the chromosome behaviour in meiosis, we performed an immunocytochemical study of primary oocytes' spread nuclei and studied chromosome synapsis during meiotic prophase I in D. unisexualis based on analysis of synaptonemal complexes (SCs). We found meiotic SC‐trivalent composed of one metacentric and two acrocentric chromosomes. We confirmed that the SC was assembled between homeologous chromosomes inherited from two parental species. Immunostaining of the pachytene and diplotene nuclei revealed a mismatch repair protein MLH1 loaded to all autosomal SC bivalents. Possible mechanisms of meiotic recombination between homeologous chromosomes are discussed.

中文翻译：

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孤雌生殖岩蜥Darevskia unisexualis同源染色体的减数分裂突触和错配修复蛋白检测

Darevksia属的高加索岩石蜥蜴的孤雌生殖物种是脊椎动物杂交的网状进化和物种形成的重要证据。在许多群体中都发现了通过种间杂交形成的仅雌性谱系。然而，提供孤雌生殖物种长期稳定性的卵子发生的关键机制和减数分裂的细节仍然未知。在这里，我们报告了二倍体孤雌生殖物种Darevskia unisexualis中体细胞核型和减数分裂前期 I 细胞核的细胞遗传学特征来自亚美尼亚的新种群“Keti”，其中包含奇数条染色体 2n = 37，而不是通常的 2n = 38。我们揭示了 36 条近着丝粒染色体和一条常染色体常染色体，这是由罗伯逊易位引起的。比较基因组杂交显示染色体融合发生在从母本物种遗传的两条染色体之间，类似于另一个孤雌生殖物种D. rostombekowi。为了追踪减数分裂中的染色体行为，我们对原代卵母细胞的扩散核进行了免疫细胞化学研究，并研究了D. unisexualis减数分裂前期 I 期间的染色体突触基于对联会复合物 (SC) 的分析。我们发现减数分裂 SC-三价体由一条中着丝粒染色体和两条近着丝粒染色体组成。我们证实 SC 是在从两个亲本物种继承的同源染色体之间组装的。粗线期和二线期细胞核的免疫染色显示错配修复蛋白 MLH1 加载到所有常染色体 SC 二价体上。讨论了同源染色体之间减数分裂重组的可能机制。