College of Life Sciences and Technology, Tarim University/Key Laboratory of Protection and Utilization of Biological Resources in Tarim Basin, Xinjiang Production & Construction Corps/Research Center of Populus Euphratica, Aral, 843300, China.
College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua, 321004, China.
Commun Biol. 2022 Nov 4;5(1):1186. doi: 10.1038/s42003-022-04145-7.
Reference-quality genomes of both sexes are essential for studying sex determination and sex-chromosome evolution, as their gene contents and expression profiles differ. Here, we present independent chromosome-level genome assemblies for the female (XX) and male (XY) genomes of desert poplar (Populus euphratica), resolving a 22.7-Mb X and 24.8-Mb Y chromosome. We also identified a relatively complete 761-kb sex-linked region (SLR) in the peritelomeric region on chromosome 14 (Y). Within the SLR, recombination around the partial repeats for the feminizing factor ARR17 (ARABIDOPSIS RESPONSE REGULATOR 17) was potentially suppressed by flanking palindromic arms and the dense accumulation of retrotransposons. The inverted small segments S1 and S2 of ARR17 exhibited relaxed selective pressure and triggered sex determination by generating 24-nt small interfering RNAs that induce male-specific hyper-methylation at the promoter of the autosomal targeted ARR17. We also detected two male-specific fusion genes encoding proteins with NB-ARC domains at the breakpoint region of an inversion in the SLR that may be responsible for the observed sexual dimorphism in immune responses. Our results show that the SLR appears to follow proposed evolutionary dynamics for sex chromosomes and advance our understanding of sex determination and the evolution of sex chromosomes in Populus.
对于研究性别决定和性染色体进化，雌雄两性的参考质量基因组都是必不可少的，因为它们的基因含量和表达谱存在差异。在这里，我们为沙漠白杨（Populus euphratica）的雌性（XX）和雄性（XY）基因组提供了独立的染色体水平基因组组装，解决了 22.7Mb 的 X 染色体和 24.8Mb 的 Y 染色体。我们还在染色体 14（Y）的端粒区域鉴定出了一个相对完整的 761kb 的性连锁区（SLR）。在 SLR 内，围绕 feminizing factor ARR17（ARABIDOPSIS RESPONSE REGULATOR 17）的部分重复的重组可能被侧翼的回文臂和大量逆转座子的积累所抑制。ARR17 的倒置小片段 S1 和 S2 表现出松弛的选择压力，并通过产生 24nt 的小干扰 RNA 来引发性别决定，该 RNA 诱导常染色体靶向 ARR17 启动子的雄性特异性超甲基化。我们还在 SLR 中反转的小片段内的断裂点区域检测到两个雄性特异性融合基因，该基因编码具有 NB-ARC 结构域的蛋白质，可能是导致观察到的免疫反应性别二态性的原因。我们的研究结果表明，SLR 似乎遵循性染色体的进化动力学，并加深了我们对杨树性别决定和性染色体进化的理解。
