NBS-Encoding Genes in Brassica napus Evolved Rapidly After Allopolyploidization and Co-localize With Known Disease Resistance Loci
NBS-Encoding Genes in Brassica napus Evolved Rapidly After Allopolyploidization and Co-localize With Known Disease Resistance Loci
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DOI：
10.3389/fpls.2019.00026
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发表时间：
2019-01-30
影响因子：
5.6
通讯作者：
Fu, Donghui
中科院分区：
文献类型：
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作者：
Fu, Ying;Zhang, Yaofeng;Fu, Donghui
含有核苷酸结合位点（NBS）的基因在植物抗病性中起着重要作用。然而，异源四倍体油菜（A（n）A（n）C（n）C（n），2n = 38）形成后NBS编码基因的进化命运仍然未知。我们对B中的puerectin功能性NBS编码基因进行了全基因组比较。napus及其祖先种芜菁（Brassica rapa，A（r）A（r），2n = 20）和甘蓝（Brassica oleracea，CoCo，2n = 18），分别鉴定出464、202和146个具有puestrophic功能的NBS编码基因，基因不均匀地分布在几个簇中。B的An亚基因组。napus与B的A（r）基因组具有相似数量的NBS编码基因（191个基因）。rapa（202个基因）和类似的聚类模式。然而，B的C-n基因组。napus比B多273个基因。甘蓝C-o基因组（146个），具有不同的聚类趋势。在B中只有97个编码NBS的基因（66.4%）。与B中的NBS编码基因同源。napus之间有176个NBS编码基因（87.1%）具有同源性，其中B. rapa和B.油菜。这些结果表明，在C基因组中编码NBS的基因可能在B形成后发生了更大的多样性。油菜。虽然大多数编码NBS的基因在B. napus似乎起源于祖先，一些NBS编码基因的出生和死亡也是由非同源重组介导的。B. napus和祖先种的遗传多样性小于1，说明在B阶段进行了纯化选择。油菜进化大多数NBS编码基因（60%）在根组织（根、叶、茎、种子和花组织类型）中表现出较高的表达水平。B 3种主要病害抗性QTL定位NBS编码基因的比较分析。油菜（黑胫病、根肿病和核盘菌茎腐病）在B中发现了204个NBS编码基因。在71个抗病QTL区间内定位到了甘蓝型油菜的抗病QTL。大部分NBS编码基因与抗单种病害的QTL共定位，47个基因与抗两种病害的QTL共定位，3个基因与抗三种病害的QTL共定位。研究结果表明，油菜NBS编码基因在不同的芸苔属亚基因组中存在显著的变异和有趣的进化轨迹，NBS编码基因和抗性QTL的共定位可能有助于油菜的抗病育种。
Genes containing nucleotide-binding sites (NBS) play an important role in pathogen resistance in plants. However, the evolutionary fate of NBS-encoding genes after formation of allotetraploid Brassica napus (A(n)A(n)C(n)C(n), 2n = 38) is still unknown. We performed a genome-wide comparison of putatively functional NBS-encoding genes in B. napus and its progenitor species Brassica rapa (A(r)A(r), 2n = 20) and Brassica oleracea (CoCo, 2n = 18), identifying 464, 202, and 146 putatively functional NBS-encoding genes respectively, with genes unevenly distributed in several clusters. The An-subgenome of B. napus possessed similar numbers of NBS-encoding genes (191 genes) to the A(r) genome of B. rapa (202 genes) and similar clustering patterns. However, the C-n genome of B. napus had many more genes (273) than the B. oleracea C-o genome (146), with different clustering trends. Only 97 NBS-encoding genes (66.4%) in B. oleracea were homologous with NBS-encoding genes in B. napus, while 176 NBS-encoding genes (87.1%) were homologous between B. rapa and B. napus. These results suggest a greater diversification of NBS-encoding genes in the C genome may have occurred after formation of B. napus. Although most NBS-encoding genes in B. napus appeared to derive from the progenitors, the birth and death of several NBS-encoding genes was also putatively mediated by non-homologous recombination. The Ka/Ks values of most homologous pairs between B. napus and the progenitor species were less than 1, suggesting purifying selection during B. napus evolution. The majority of NBS-encoding genes (60% in all species) showed higher expression levels in root tissue (out of root, leaf, stem, seed and flower tissue types). Comparative analysis of NBS-encoding genes with mapped resistance QTL against three major diseases of B. napus (blackleg, clubroot and Sclerotinia stem rot) found 204 NBS-encoding genes in B. napus located within 71 resistance QTL intervals. The majority of NBS-encoding genes were co-located with resistance QTLs against a single disease, while 47 genes were co-located with QTLs against two diseases and 3 genes were co-located with QTLs against all three. Our results revealed significant variation as well as interesting evolutionary trajectories of NBS-encoding genes in the different Brassica subgenomes, while co-localization of NBS-encoding genes and resistance QTL may facilitate resistance breeding in oilseed rape.