Heterosis or hybrid vigor has been used widely for more than a decade in Canola (Brassica napus) production. Canola hybrids show heterosis in a variety of traits compared to parents, including increased biomass at the early stages of seedling establishment, which is a critical developmental step that impacts future plant growth and seed yield. In this study, we examined transcriptomes of two parental lines, Garnet (Gar) and NX0052 (0052), and their reciprocal hybrids, Gar/0052, at 4 and 8 days after sowing (DAS). In hybrids, early seedling biomass heterosis is correlated with earlier expression of genes in photosynthesis pathways relative to parents. The hybrids also showed early expression of genes in the auxin biosynthesis pathway, consistent with the higher auxin concentrations detected in hybrid seedlings at 4 DAS. Auxin is a key phytohormone that regulates plant development promoting cell expansion and cell proliferation. Consistent with the increased levels of auxin, hybrids have larger and more palisade cells than the parents at the same time point. We propose a possible mechanism of early biomass heterosis through the early establishment of photosynthesis and auxin biosynthesis, providing insights into how transcriptional changes in hybrids are translated into phenotypical heterosis. This finding could be utilized in future Canola breeding to identify hybrid combinations with the superior early seedling establishment and strong levels of hybrid vigor in later plant development.

中文翻译：

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早期建立的光合作用和生长素的生物合成在甘蓝型油菜（Canola）杂种的早期生物量杂种优势中起关键作用。

杂种优势或杂种优势已在油菜中广泛应用了十多年（甘蓝型油菜）） 生产。与亲本相比，低芥酸菜子杂种表现出多种性状杂种优势，包括在幼苗建立初期生物量增加，这是影响未来植物生长和种子产量的关键发展步骤。在这项研究中，我们检查了两个亲本系石榴石（Garnet）和NX0052（0052）的转录组，以及它们的倒交杂种Gar / 0052，分别在播种后4和8天（DAS）进行了检查。在杂种中，相对于亲本，早期幼苗生物量杂种优势与光合作用途径中基因的早期表达相关。杂种还显示了生长素生物合成途径中的基因早期表达，这与在4 DAS下在杂种幼苗中检测到的较高的生长素浓度一致。生长素是调节植物发育，促进细胞扩增和细胞增殖的关键植物激素。与生长素水平的增加一致，杂种在同一时间点具有比亲本更大和更多的栅栏细胞。我们提出了通过早期建立光合作用和生长素生物合成来实现早期生物量杂种优势的可能机制，从而提供了有关杂种中转录变化如何转化为表型杂种优势的见解。这一发现可用于将来的卡诺拉油菜育种中，以鉴定具有较早的幼苗建立和较强的杂种活力水平的杂种组合，以促进后期植物的发育。提供有关如何将杂种中的转录变化转化为表型杂种优势的见解。这一发现可用于将来的卡诺拉油菜育种中，以鉴定具有较早的幼苗建立和较强的杂种活力水平的杂种组合，以促进后期植物的发育。提供有关如何将杂种中的转录变化转化为表型杂种优势的见解。这一发现可用于将来的卡诺拉油菜育种中，以鉴定具有较早的幼苗建立和较强的杂种活力水平的杂种组合，以促进后期植物的发育。