Species-specific genomic imprinting is an epigenetic phenomenon leading to parent-of-origin-specific differential expression of maternally and paternally inherited alleles. To date, no studies of imprinting have been reported in rapeseed, a tetraploid species. Here, we analysed global patterns of allelic gene expression in developing rapeseed endosperms from reciprocal crosses between inbred lines YN171 and 93275. A total of 183 imprinted genes, consisting of 167 maternal expressed genes (MEGs) and 16 paternal expressed genes (PEGs), were identified from 14,394 genes found to harbour diagnostic SNPs between the parental lines. Some imprinted genes were validated in different endosperm stages and other parental combinations by RT-PCR analysis. A clear clustering of imprinted genes throughout the rapeseed genome was identified, which was different from most other plants. Methylation analysis of 104 out of the 183 imprinted genes showed that 11 genes (7 MEGs and 4 PEGs) harboured differentially methylated regions (DMRs). Unexpectedly, only 1 MEG out of these 11 genes had a DMR that exhibited high CG methylation rate in paternal allele and had big difference between parent alleles. These results extend our understanding of gene imprinting in plants and provide potential avenues for further research in imprinted genes.

中文翻译：

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全基因组范围内油菜籽（甘蓝型油菜）胚乳中印迹基因的筛选和分析。

物种特有的基因组印迹是一种表观遗传现象，可导致母本和父本遗传的等位基因的原产地特异性差异表达。迄今为止，还没有关于四倍体油菜籽的印迹研究的报道。在这里，我们分析了自交系YN171和93275之间相互杂交的油菜胚乳发育过程中等位基因基因表达的总体模式。共有183个印迹基因，包括167个母体表达基因（MEG）和16个父本表达基因（PEG）。从发现的14394个基因中鉴定出这些基因，这些基因在亲本系之间具有诊断性SNP。通过RT-PCR分析，在不同的胚乳阶段和其他亲本组合中验证了某些印迹基因。确定了整个油菜基因组中印迹基因的清晰簇，与大多数其他植物不同。183个印迹基因中的104个进行了甲基化分析，结果显示11个基因（7个MEG和4个PEG）具有差异甲基化区域（DMR）。出乎意料的是，这11个基因中只有1个MEG具有DMR，该DMR在父本等位基因中表现出高的CG甲基化率，并且在亲本等位基因之间具有很大的差异。这些结果扩展了我们对植物基因印迹的理解，并为印迹基因的进一步研究提供了潜在的途径。