Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, China.
State Key Laboratory of Grassland Agro-Ecosystem, Institute of Innovation Ecology and College of Life Sciences, Lanzhou University, Lanzhou, China.
Mol Biol Evol. 2021 Mar 9;38(3):968-980. doi: 10.1093/molbev/msaa261.
Dioecy, the presence of separate sexes on distinct individuals, has evolved repeatedly in multiple plant lineages. However, the specific mechanisms by which sex systems evolve and their commonalities among plant species remain poorly understood. With both XY and ZW sex systems, the family Salicaceae provides a system to uncover the evolutionary forces driving sex chromosome turnovers. In this study, we performed a genome-wide association study to characterize sex determination in two Populus species, P. euphratica and P. alba. Our results reveal an XY system of sex determination on chromosome 14 of P. euphratica, and a ZW system on chromosome 19 of P. alba. We further assembled the corresponding sex-determination regions, and found that their sex chromosome turnovers may be driven by the repeated translocations of a Helitron-like transposon. During the translocation, this factor may have captured partial or intact sequences that are orthologous to a type-A cytokinin response regulator gene. Based on results from this and other recently published studies, we hypothesize that this gene may act as a master regulator of sex determination for the entire family. We propose a general model to explain how the XY and ZW sex systems in this family can be determined by the same RR gene. Our study provides new insights into the diversification of incipient sex chromosomes in flowering plants by showing how transposition and rearrangement of a single gene can control sex in both XY and ZW systems.
雌雄异株，即不同个体具有明显的雌雄性别，在多个植物谱系中多次进化。然而，性系统进化的具体机制及其在植物物种中的共性仍知之甚少。杨柳科家族同时具有 XY 和 ZW 性系统，为揭示驱动性染色体倒位的进化力量提供了一个系统。在这项研究中，我们进行了全基因组关联研究，以描述两种杨属植物，胡杨和白杨的性别决定。我们的研究结果揭示了胡杨 14 号染色体上的 XY 性别决定系统，以及白杨 19 号染色体上的 ZW 性别决定系统。我们进一步组装了相应的性别决定区域，并发现它们的性染色体倒位可能是由一个类似 Helitron 的转座子的重复易位驱动的。在易位过程中，这个因子可能捕获了部分或完整的序列，这些序列与 A 型细胞分裂素反应调节基因同源。基于这项研究和其他最近发表的研究结果，我们假设这个基因可能作为整个家族性别决定的主调控因子。我们提出了一个一般模型，来解释为什么这个家族的 XY 和 ZW 性系统可以由同一个 RR 基因决定。我们的研究通过展示单个基因的转座和重排如何控制 XY 和 ZW 系统中的性别，为研究有花植物初生性染色体的多样化提供了新的见解。
