Species and Population Level Molecular Profiling Reveals Cryptic Recombination and Emergent Asymmetry in the Dimorphic Mating Locus of C. reinhardtii
Species and Population Level Molecular Profiling Reveals Cryptic Recombination and Emergent Asymmetry in the Dimorphic Mating Locus of C. reinhardtii
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DOI：
10.1371/journal.pgen.1003724
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发表时间：
2013-08-01
期刊：
影响因子：
4.5
通讯作者：
Umen, James G.
中科院分区：
文献类型：
--
作者：
De Hoff, Peter L.;Ferris, Patrick;Umen, James G.
异型性性别决定区或交配型基因座可以包含大区域的非重组序列，其中选择在与自由重组的常染色体区域不同的约束下进行。对这些非重组区域的详细研究可以深入了解基因是如何获得和丢失的，以及交配单倍型或性染色体之间如何保持遗传隔离。莱茵衣藻交配型基因座（MT）是一个复杂的多基因区域，其特征在于其两个单倍型MT+和MT-之间的序列重排和抑制重组。我们使用新的序列信息来重新定义MT的遗传内容，并发现了几个新发现的基因的常染色体重复易位以及性控制的表达模式。我们检测了野生型C. reinhardtii进行研究重组抑制的影响。我们的人口数据揭示了两个以前未报道的类型的遗传交换衣原体MT基因转换重排的结构域，和交叉交换侧翼域，这两个有助于维护单倍型之间的遗传同质性。为了调查MT中重组受阻的原因，我们评估了亲本在MT纯合的杂交中的重组率。虽然在MT+ xMT+杂交中恢复了正常重组，但在MT-xMT-杂交中仍受到抑制。这些数据揭示了两个MT单倍型的潜在不对称性，并表明序列重排不足以完全解释重组抑制。我们的研究结果揭示了交配位点的新的进化动力学，并对异形性染色体和其他非重组基因组区域的进化产生了影响。
Heteromorphic sex-determining regions or mating-type loci can contain large regions of non-recombining sequence where selection operates under different constraints than in freely recombining autosomal regions. Detailed studies of these non-recombining regions can provide insights into how genes are gained and lost, and how genetic isolation is maintained between mating haplotypes or sex chromosomes. The Chlamydomonas reinhardtii mating-type locus (MT) is a complex polygenic region characterized by sequence rearrangements and suppressed recombination between its two haplotypes, MT+ and MT-. We used new sequence information to redefine the genetic contents of MT and found repeated translocations from autosomes as well as sexually controlled expression patterns for several newly identified genes. We examined sequence diversity of MT genes from wild isolates of C. reinhardtii to investigate the impacts of recombination suppression. Our population data revealed two previously unreported types of genetic exchange in Chlamydomonas MT-gene conversion in the rearranged domains, and crossover exchanges in flanking domains-both of which contribute to maintenance of genetic homogeneity between haplotypes. To investigate the cause of blocked recombination in MT we assessed recombination rates in crosses where the parents were homozygous at MT. While normal recombination was restored in MT+ xMT+ crosses, it was still suppressed in MT-xMT- crosses. These data revealed an underlying asymmetry in the two MT haplotypes and suggest that sequence rearrangements are insufficient to fully account for recombination suppression. Together our findings reveal new evolutionary dynamics for mating loci and have implications for the evolution of heteromorphic sex chromosomes and other non-recombining genomic regions.