Karyotype Stability and Unbiased Fractionation in the Paleo-Allotetraploid Cucurbita Genomes
Karyotype Stability and Unbiased Fractionation in the Paleo-Allotetraploid Cucurbita Genomes
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DOI：
10.1016/j.molp.2017.09.003
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发表时间：
2017-10-09
期刊：
影响因子：
27.5
通讯作者：
Xu, Yong
中科院分区：
文献类型：
--
作者：
Sun, Honghe;Wu, Shan;Xu, Yong
葫芦属包含葫芦科中几个重要的经济物种。在这里，我们报告了 C. maxima 和 C. moschata 的高质量基因组序列，并提供了支持葫芦属异源四倍体化事件的证据。我们能够根据与Benincaseae部落中甜瓜、黄瓜和西瓜的不同遗传距离，将基因组划分为两个同源亚基因组。我们估计，这两个二倍体祖先分别在大约 31 和 2600 万年前 (Mya) 相继从 Benincaseae 中分化出来，异源四倍体化发生在 26 Mya 和 3 Mya 之间的某个时间点，即 C. maxima 和 C. moschata 分化的估计日期。亚基因组在很大程度上保持了其二倍体祖先的染色体结构。多倍体化后的这种长期核型稳定性在植物多倍体中尚未常见。这两个亚基因组保留了相似数量的基因，并且两个亚基因组在基因表达方面都不具有全局优势。 C. maxima x C. moschata 种间 F-1 杂种及其两个亲本中的等位基因特异性表达分析表明，亲本表达差异背后的反式调节效应占主导地位，并检测了与重要农艺性状中的杂种优势相关的杂种中的越行基因表达变化。我们的研究为多倍体基因组进化提供了见解，并为葫芦科作物的遗传改良提供了宝贵的资源。
The Cucurbita genus contains several economically important species in the Cucurbitaceae family. Here, we report high-quality genome sequences of C. maxima and C. moschata and provide evidence supporting an allotetraploidization event in Cucurbita. We are able to partition the genome into two homoeologous subgenomes based on different genetic distances to melon, cucumber, and watermelon in the Benincaseae tribe. We estimate that the two diploid progenitors successively diverged from Benincaseae around 31 and 26 million years ago (Mya), respectively, and the allotetraploidization happened at some point between 26 Mya and 3 Mya, the estimated date when C. maxima and C. moschata diverged. The subgenomes have largely maintained the chromosome structures of their diploid progenitors. Such long-term karyotype stability after polyploidization has not been commonly observed in plant polyploids. The two subgenomes have retained similar numbers of genes, and neither subgenome is globally dominant in gene expression. Allele-specific expression analysis in the C. maxima x C. moschata interspecific F-1 hybrid and their two parents indicates the predominance of trans-regulatory effects underlying expression divergence of the parents, and detects transgressive gene expression changes in the hybrid correlated with heterosis in important agronomic traits. Our study provides insights into polyploid genome evolution and valuable resources for genetic improvement of cucurbit crops.