CEITEC - Central European Institute of Technology, Masaryk University, Brno, CZ-625 00, Czech Republic.
National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Brno, CZ-625 00, Czech Republic.
Plant Physiol. 2022 Aug 29;190(1):403-420. doi: 10.1093/plphys/kiac268.
Angiosperm genome evolution was marked by many clade-specific whole-genome duplication events. The Microlepidieae is one of the monophyletic clades in the mustard family (Brassicaceae) formed after an ancient allotetraploidization. Postpolyploid cladogenesis has resulted in the extant c. 17 genera and 60 species endemic to Australia and New Zealand (10 species). As postpolyploid genome diploidization is a trial-and-error process under natural selection, it may proceed with different intensity and be associated with speciation events. In Microlepidieae, different extents of homoeologous recombination between the two parental subgenomes generated clades marked by slow ("cold") versus fast ("hot") genome diploidization. To gain a deeper understanding of postpolyploid genome evolution in Microlepidieae, we analyzed phylogenetic relationships in this tribe using complete chloroplast sequences, entire 35S rDNA units, and abundant repetitive sequences. The four recovered intra-tribal clades mirror the varied diploidization of Microlepidieae genomes, suggesting that the intrinsic genomic features underlying the extent of diploidization are shared among genera and species within one clade. Nevertheless, even congeneric species may exert considerable morphological disparity (e.g. in fruit shape), whereas some species within different clades experience extensive morphological convergence despite the different pace of their genome diploidization. We showed that faster genome diploidization is positively associated with mean morphological disparity and evolution of chloroplast genes (plastid-nuclear genome coevolution). Higher speciation rates in perennials than in annual species were observed. Altogether, our results confirm the potential of Microlepidieae as a promising subject for the analysis of postpolyploid genome diploidization in Brassicaceae.
被子植物的基因组进化受到许多分支特异性全基因组复制事件的影响。Microlepidieae 是芥菜科（Brassicaceae）中的一个单系分支，是由古老的异源四倍化形成的。多倍体化后支序分化导致现存约 17 属和 60 种澳大利亚和新西兰特有种（10 种）。由于多倍体化后基因组二倍体化是自然选择下的试错过程，它可能以不同的强度进行，并与物种形成事件相关。在 Microlepidieae 中，两个亲本亚基因组之间同源重组的不同程度导致了以慢（冷）或快（热）基因组二倍体化为特征的支序。为了更深入地了解 Microlepidieae 多倍体化后基因组的进化，我们使用完整的叶绿体序列、整个 35S rDNA 单元和丰富的重复序列分析了该族的系统发育关系。四个恢复的族内支序反映了 Microlepidieae 基因组的不同二倍体化程度，表明在一个支序内，导致二倍体化程度的内在基因组特征在属和种间是共享的。然而，即使是同属的物种也可能表现出相当大的形态差异（例如果实形状），而不同支序内的一些物种尽管基因组二倍体化的速度不同，但却经历了广泛的形态趋同。我们表明，更快的基因组二倍体化与平均形态差异和叶绿体基因进化（质体-核基因组协同进化）呈正相关。在多年生植物中观察到的物种形成率高于一年生植物。总之，我们的结果证实了 Microlepidieae 作为分析 Brassicaceae 多倍体化后基因组二倍体化的一个有前途的课题的潜力。
