Yin Tongming, Difazio Stephen P, Gunter Lee E, Zhang Xinye, Sewell Michell M, Woolbright Scott A, Allan Gery J, Kelleher Collin T, Douglas Carl J, Wang Mingxiu, Tuskan Gerald A
Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
Genome Res. 2008 Mar;18(3):422-30. doi: 10.1101/gr.7076308. Epub 2008 Feb 6.
The genus Populus consists of dioecious woody species with largely unknown genetic mechanisms for gender determination. We have discovered genetic and genomic features in the peritelomeric region of chromosome XIX that suggest this region of the Populus genome is in the process of developing characteristics of a sex chromosome. We have identified a gender-associated locus that consistently maps to this region. Furthermore, comparison of genetic maps across multiple Populus families reveals consistently distorted segregation within this region. We have intensively characterized this region using an F(1) interspecific cross involving the female genotype that was used for genome sequencing. This region shows suppressed recombination and high divergence between the alternate haplotypes, as revealed by dense map-based genome assembly using microsatellite markers. The suppressed recombination, distorted segregation, and haplotype divergence were observed only for the maternal parent in this cross. Furthermore, the progeny of this cross showed a strongly male-biased sex ratio, in agreement with Haldane's rule that postulates that the heterogametic sex is more likely to be absent, rare, or sterile in interspecific crosses. Together, these results support the role of chromosome XIX in sex determination and suggest that sex determination in Populus occurs through a ZW system in which the female is the heterogametic gender.
杨属由雌雄异株的木本物种组成，其性别决定的遗传机制很大程度上未知。我们在第十九号染色体的近着丝粒区域发现了遗传和基因组特征，这表明杨树基因组的该区域正处于发育成性染色体特征的过程中。我们鉴定出了一个始终定位于该区域的性别相关位点。此外，对多个杨树家族遗传图谱的比较揭示了该区域内始终存在的分离扭曲现象。我们使用涉及用于基因组测序的雌性基因型的F(1)种间杂交对该区域进行了深入表征。如使用微卫星标记基于图谱的密集基因组组装所揭示的，该区域显示出重组抑制以及交替单倍型之间的高度差异。在这个杂交中，仅在母本中观察到了重组抑制、分离扭曲和单倍型差异。此外，该杂交的后代显示出强烈的雄性偏向性性别比，这与霍尔丹法则一致，该法则假定在种间杂交中异配性别更有可能缺失、稀少或不育。总之，这些结果支持了第十九号染色体在性别决定中的作用，并表明杨树的性别决定是通过ZW系统发生的，其中雌性是异配性别。
