• Adventitious root (AR) formation is critically important in vegetative propagation through cuttings in some plants, especially woody species. However, the underlying molecular mechanisms remain elusive.
• Here, we report the identification of a poplar homeobox gene, PuHox52, which was induced rapidly (within 15 min) at the basal ends of stems upon cutting and played a key regulatory role in adventitious rooting. We demonstrated that overexpression of PuHox52 significantly increased the number of ARs while suppression of PuHox52 had the opposite effect.
• A multilayered hierarchical gene regulatory network (ML‐hGRN) mediated by PuHox52 was reverse‐engineered and demonstrated to govern AR formation. PuHox52 regulated AR formation through upregulation of nine hub regulators, including a jasmonate signaling pathway gene, PuMYC2, and an auxin signaling pathway gene, PuAGL12. We also identified coherent type 4 feed‐forward loops within this ML‐hGRN; PuHox52 repressed PuHDA9, which encodes a histone deacetylase, and led to an increase in acetylation and presumably expression of three hub regulators, PuWRKY51, PuLBD21 and PuIAA7.
• Our results indicate that the ML‐hGRN mediated by PuHox52 governs AR formation at the basal ends of stem cuttings from poplar trees.

中文翻译：

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PuHox52介导的分层多层基因调控网络促进了毛白杨不定根的形成。

• 不定根（AR）的形成对于某些植物（尤其是木本植物）中插条的无性繁殖至关重要。但是，潜在的分子机制仍然难以捉摸。
• 在这里，我们报道了杨木同源盒基因PuHox52的鉴定，该基因在切割后迅速（在15分钟内）在茎的基端被诱导，并且在不定根中起着关键的调节作用。我们证明，PuHox52的过表达显着增加了AR的数量，而抑制PuHox52则具有相反的作用。
• 由PuHox52介导的多层层次基因调控网络（ML-hGRN）经过逆向工程并证明可控制AR的形成。PuHox52通过上调9个枢纽调节因子来调节AR的形成，包括茉莉酸酯信号通路基因PuMYC2和生长素信号通路基因PuAGL12。我们还在此ML-hGRN中确定了相干的4类前馈环路。PuHox52抑制了编码组蛋白脱乙酰基酶的PuHDA9，并导致乙酰化的增强和推测的三种枢纽调节子PuWRKY51，PuLBD21和PuIAA7的表达。
• 我们的结果表明，由PuHox52介导的ML-hGRN决定了杨树茎干基部基端的AR形成。