Spring-type canola produces significantly smaller and less vigorous roots than winter type at later growth stages. To identify the gene-regulatory networks and cross talks among phytohormones that may be responsible for the difference between the root system of the two growth types, we analyzed transcriptomes from the root samples collected at two time points, 30 and 60 days. Out of 169,646 transcripts that were analyzed, 582 and 555 transcripts were found to be significantly differentially expressed between spring and winter types at 30 and 60 days, respectively. Several auxin-responsive genes were significantly differentially expressed between spring and winter types at both time points, but no distinct pattern of differential regulation was observed in either of the growth types. Type-A and type-B ARABIDOPSIS RESPONSE REGULATOR (ARR) genes, and gene sets involved in cytokinin signaling pathway, were upregulated in the spring types at 60 days. This would be consistent with higher cytokinin activity, which is known to inhibit root growth, in spring type root system at the later growth stage. In addition, several gibberellin-responsive and gibberellin-signaling gene sets were also upregulated only in spring types at 60 days. We observed an elongated root system with fewer root branches in spring type compared to winter type at 60 days in this study, which is consistent with a role of gibberellin in root growth and development. Extensive gene expression data generated in this research will further assist in understanding the natural variation of root system in canola growth habits.

在生长后期，春季型油菜产生的根比冬季类型的油菜要小得多，并且活力较小。为了确定可能导致两种生长类型根系差异的植物激素之间的基因调控网络和串扰，我们分析了在30天和60天两个时间点收集的根样品的转录组。在分析的169,646个笔录中，分别在30天和60天的春季和冬季类型之间分别有582和555个笔录显着差异表达。在两个时间点上，春季和冬季类型之间的几个生长素应答基因均显着差异表达，但在两种生长类型中均未观察到明显的差异调节模式。A型和B型春季类型中，第60天，拟南芥反应调节因子（ARR）基因和涉及细胞分裂素信号传导途径的基因集被上调。这与较高的细胞分裂素活性相一致，后者在春季的根部生长阶段，可抑制根的生长。此外，仅在春季类型的第60天，一些赤霉素反应和赤霉素信号转导的基因组也被上调。在这项研究中，我们观察到60天春季类型的根系比冬季类型的根系细长，而冬季类型较少，这与赤霉素在根系生长和发育中的作用是一致的。这项研究中产生的大量基因表达数据将进一步帮助理解油菜生长习惯中根系的自然变异。