Background

Parent-of-origin gene expression and its role in seed development have drown a great attention in recent years. Genome-wide analysis has identified hundreds of candidate imprinted genes, a major type of parent-of-origin genes, in rice hybrid endosperms at the stage of 5 days after pollination (dap). However, the expression of these genes in early endosperm have been never confirmed due to technique limitations and the behavior of the imprinted genes in different rice hybridizations are still largely unknown.

Results

Here, based on our elaborate technique established previously, the expression patterns of PcG genes in the early stages of endosperm development (within 3 dap), were comprehensively analyzed. We revealed that the free nucleus stage of endosperm development is critical for parent-of-origin gene analysis. The expression of the imprinted genes are highly dynamic, likely corresponding to the critical developmental events during this period. Hybridizations between Oryza sativa japonica and indica showed that the expression patterns of the same imprinted gene could be varied by crossing with different parental cultivars, indicative of their parent-dependent character. There are strong alleles that often showed predominant expression over other alleles regardless of the parental origin, which provides a possible explanation for the cultivar-dependent predominant phenotype in crop hybridizations. In addition, we found that the transcripts of the same gene behave differently, with imprinting or non-imprinting patterns, suggesting the existence of not only imprinted and non-imprinted genes but also imprinted or non-imprinted transcripts, which reveals new aspects of the genomic imprinting.

Conclusions

These findings on the characters of parent-of-origin genes shed light on the understanding the real role of gene imprinting in endosperm development.

中文翻译：

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对亚种杂交中水稻早期胚乳发育过程中Polycomb组基因表达动态的详细观察揭示了其起源母基因的特征。

背景

近年来，起源于母体的基因表达及其在种子发育中的作用备受关注。全基因组分析已在授粉（dap）后5天阶段鉴定了水稻杂种胚乳中数百个候选印迹基因，这是起源于父本的主要基因类型。然而，由于技术限制，从未确认这些基因在早期胚乳中的表达，而且在不同水稻杂交中印迹基因的行为仍是很大程度上未知的。

结果

在此，根据我们先前建立的精细技术，全面分析了胚乳发育早期（3 dap内）PcG基因的表达模式。我们揭示了胚乳发育的自由核阶段对于起源母体基因分析至关重要。印迹基因的表达是高度动态的，可能与这一时期的关键发育事件相对应。水稻之间的杂交粳稻和in稻显示，通过与不同的亲本品种杂交，可以改变同一印迹基因的表达方式，这表明它们具有亲本依赖性。不论亲本来源如何，都有强等位基因通常比其他等位基因表现出优势表达，这为作物杂交中依赖品种的优势表型提供了可能的解释。此外，我们发现同一基因的转录本表现不同，具有印迹或非印迹模式，这表明不仅存在印迹和非印迹基因，而且还存在印迹或非印迹基因，这揭示了该基因的新方面。基因组印记。

结论

这些关于起源基因特征的发现为理解基因印记在胚乳发育中的真正作用提供了启示。