背景回顾：Polyploidy is a major evolutionary force that has shaped plant diversity. 

提出问题：However, the various pathways toward polyploid formation and interploidy gene flow remain poorly understood. 

主要发现：Here, we demonstrated that the immediate progeny of allotriploid AAC Brassica (obtained by crossing allotetraploid Brassica napus and diploid Brassica rapa) was predominantly aneuploids with ploidal levels ranging from near-triploidy to near-hexaploidy, and their chromosome numbers deviated from the theoretical distribution toward increasing chromosome numbers, suggesting that they underwent selection. 

结果1-染色体平衡与育性：Karyotype and phenotype analyses showed that aneuploid individuals containing fewer imbalanced chromosomes had higher viability and fertility. 

结果2-异源三倍体的“桥梁”作用：Within three generations of self-fertilization, allotriploids mainly developed into near or complete allotetraploids similar to B. napus via gradually increasing chromosome numbers and fertility, suggesting that allotriploids could act as a bridge in polyploid formation, with aneuploids as intermediates. 

结果3-二倍体向异源四倍体的基因流：Self-fertilized interploidy hybrids ultimately generated new allopolyploids carrying different chromosome combinations, which may create a reproductive barrier preventing allotetraploidy back to diploidy and promote gene flow from diploids to allotetraploids. 

结论：These results suggest that the maintenance of a proper genome balance and dosage drove the recurrent conversion of allotriploids to allotetraploids, which may contribute to the formation and evolution of polyploids.

多倍体是一种驱动植物多样性的主要演化动力。但是，作用于多倍体形成的途径多种多样，目前对于不同倍体之间的基因流理解较少。本文中，作者发现在异源四倍体欧洲油菜和二倍体芜菁杂交形成的异源三倍体物种（AAC）中，其直系子代以非整倍体为主，倍性水平从近三倍体到近六倍体不等，并且其染色体数目明显较预期分布有所增加，表明其经历了选择。核型和表型分析显示，具有更少不平衡染色体的非整倍体的个体，具有更高的活力和育性。在自交三代内，异源三倍体通过增加染色体数据和育性，大多形成了类似于欧洲油菜的近乎或者完全的异源四倍体，说明异源三倍体可能在多倍体形成过程中发挥着“桥梁”作用，而非整倍体则作为中间体发挥作用。倍体间杂种的自交会产生新的含有不同染色体组合的异源多倍体，这可能创造了一个生殖障碍以阻止异源四倍体回到二倍体，并促进二倍体向异源四倍体的基因流。这些结果表明，一个恰当的基因组平衡和剂量的维持驱动了异源三倍体向异源四倍体的反复转变，这可能作用于多倍体的形成和演化。

** 熊志勇 **