University of Sciences and Technology Houari Boumedienne USTHB, Faculty of Biological Sciences FSB, Laboratory of Biology and Physiology of Organisms LBPO, Bab-Ezzouar, El-Alia, BP 32, 16111, Algiers, Algeria.
INRAE, Agrocampus Ouest, Université de Rennes, UMR IGEPP, 35650, Le Rheu, France.
Plant Reprod. 2020 Mar;33(1):43-58. doi: 10.1007/s00497-020-00385-x. Epub 2020 Feb 20.
Polyploidy or whole genome duplication is a frequent and recurrent phenomenon in flowering plants that has played a major role in their diversification, adaptation and speciation. The adaptive success of polyploids relates to the different evolutionary fates of duplicated genes. In this study, we explored the impact of the whole genome triplication (WGT) event in the Brassiceae tribe on the genes involved in the self-incompatibility (SI) signalling pathway, a mechanism allowing recognition and rejection of self-pollen in hermaphrodite plants. By taking advantage of the knowledge acquired on this pathway as well as of several reference genomes in Brassicaceae species, we determined copy number of the different genes involved in this pathway and investigated their structural and functional evolutionary dynamics. We could infer that whereas most genes involved in the SI signalling returned to single copies after the WGT event (i.e. ARC1, JDP1, THL1, THL2, Exo70A01) in diploid Brassica species, a few were retained in duplicated (GLO1 and PLDα) or triplicated copies (MLPK). We also carefully studied the gene structure of these latter duplicated genes (including the conservation of functional domains and active sites) and tested their transcription in the stigma to identify which copies seem to be involved in the SI signalling pathway. By taking advantage of these analyses, we then explored the putative origin of a contrasted SI phenotype between two Brassica rapa varieties that have been fully sequenced and shared the same S-allele (S60).
多倍体或全基因组加倍是开花植物中频繁发生的现象，它在植物的多样化、适应和物种形成中发挥了重要作用。多倍体的适应性成功与重复基因的不同进化命运有关。在这项研究中，我们探讨了 Brassiceae 族的全基因组三倍化（WGT）事件对涉及自交不亲和（SI）信号通路的基因的影响，这是一种允许雌雄同体植物识别和排斥自身花粉的机制。利用我们在该途径上获得的知识以及几种 Brassicaceae 物种的参考基因组，我们确定了参与该途径的不同基因的拷贝数，并研究了它们的结构和功能进化动态。我们可以推断，尽管大多数参与 SI 信号通路的基因在 WGT 事件后（即 ARC1、JDP1、THL1、THL2、Exo70A01）回到了二倍体 Brassica 物种的单拷贝，但少数基因保留了重复（GLO1 和 PLDα）或三倍拷贝（MLPK）。我们还仔细研究了这些重复基因的基因结构（包括功能域和活性位点的保守性），并测试了它们在柱头中的转录，以确定哪些拷贝似乎参与了 SI 信号通路。通过利用这些分析，我们探讨了两个已完全测序且具有相同 S 等位基因（S60）的 Brassica rapa 品种之间具有对比性 SI 表型的可能起源。
