显花植物自交不亲和S-位点重组抑制分子机理的研究

Homologous chromosomes of maternal and paternal origins recombine and exchange the genetic materials during the first meiotic division in the life cycle of sexually reproducing eukaryotes. The recombination frequency is not uniform along chromosomes with higher or lower rates of recombination associated with different chromosome regions. Recombination suppression occurs as a result of extremely lower rate of exchange between homologous chromosomes. The S-locus is a single multi-allelic locus that controls self-incompatibility in many flowering plants. The S-locus F-box (SLF), encoding the pollen determinant, has been postulated to specially detoxify its non-self S-ribonucleases (S-RNases) which is allelic products of the pistil determinant. S-RNase is tightly linked with SLFs to form a complex locus. It has been shown that the recombination rate within this complex locus is fully suppressed during meiosis. Recombination suppression within the S-locus is proposed to be a genetic mechanism that prevent self-fertilization and promote outcrossing to generate genetic diversity. However, the molecular mechanism for this recombination suppression remains elusive. Previously, we located the S-locus of Antirrhinum in a heterochromatic region on the chromosome 8 and found DNA and histone methylations were associated with this region. To address their roles in the S-locus suppression, in this study, we propose to perform a genetic linkage analysis for different S-haplotypes and detailed studies on their chromosome structure as well as their DNA and histone methylation status. We believe that the data obtained in this study will provide novel insights into the molecular mechanisms of the suppressed recombination around the S-locus in Antirrhinum and impact our further understanding of DNA recombination suppression and its potential application in crop breeding by enhancing recombination rate.

减数分裂同源重组过程中发生交换的频率并不是均一的，存在着较高和较低重组率的区域，重组抑制是交换率严重降低的一种现象。在S-核酸酶介导的植物自交不亲和系统中，花柱特异的S-核酸酶与花粉特异的SLF紧密连锁几乎不发生重组。若重组则会打破自交不亲和性的遗传传递，其重组后代不能再特异地识别自己与异己。人们对S-位点重组抑制的分子机理知之甚少。我们在前期工作中，定位了自交不亲和模式植物金鱼草的S-位点位于第8号染色体异染色质区，且该区域的DNA和组蛋白存在甲基化现象。为深入研究这些现象和重组抑制之间的关系，本项目拟通过对金鱼草不同单倍体型S-位点的连锁分析，绘制该区域的精细遗传和物理图谱，并结合染色体结构、基因组特征以及表观遗传学调控等来阐释S-位点的重组抑制现象。预期研究结果一方面对理解S-位点结构和功能有帮助，同时对了解DNA重组抑制的分子机制和如何在育种中提高重组频率增加遗传变异有指导意义。

自交不亲和性是显花植物的一个种内生殖隔离机制，本研究对自交不亲和模式植物金鱼草的自交不亲和S-位点---第8号染色体异染色质区以及全基因组进行了深度数据挖掘分析，绘制出该区域的精细遗传和物理图谱，通过对金鱼草不同单倍体型S-位点的连锁分析，并结合染色体结构、基因组特征阐释S-位点的重组抑制和进化现象，为进一步挖掘S-位点相关基因的功能研究提供了遗传基础，同时对了解DNA重组抑制的分子机制和如何在育种中提高重组频率增加遗传变异具有指导意义。