Lateral root (LR) initiation is controlled by the pericycle and the neighboring endodermis in Arabidopsis. Here, we demonstrate that UBIQUITIN-SPECIFIC PROTEASE14/DA3 regulates LR initiation by modulating auxin signaling in the pericycle and endodermis. DA3 negatively affects the mRNA and protein levels of AUXIN RESPONSE FACTOR7 (ARF7) and ARF19 in the pericycle and endodermis but positively regulates the protein stability of SHORT HYPOCOTYL 2 (SHY2/IAA3), an auxin signaling repressor, in the endodermis. We show that DA3 interacts with ARF7 and ARF19, inhibiting their binding to the locus of LATERAL ORGAN BOUNDARY DOMAIN16 (LBD16) to repress its expression in the pericycle. SHY2 also interacts with ARF7 and ARF19 in the endodermis and enhances the DA3 repressive effect on ARF7 and ARF19, thus modulating LBD16 expression in the pericycle. Overall, our findings show that DA3 acts with SHY2, ARF7, and ARF19 to coordinate auxin signaling in the pericycle and endodermis to control LR initiation in Arabidopsis.

拟南芥中的侧根 (LR) 起始由中柱鞘和邻近的内皮控制。在这里，我们证明泛素特异性蛋白酶 14/DA3 通过调节中柱周和内皮中的生长素信号来调节 LR 启动。DA3 对中柱周和内皮层中 AUXIN RESPONSE FACTOR7 (ARF7) 和 ARF19 的 mRNA 和蛋白水平产生负面影响，但对内皮层中生长素信号转导抑制因子 SHORT HYPOCOTYL 2 (SHY2/IAA3) 的蛋白稳定性产生正向调节。我们显示 DA3 与 ARF7 和 ARF19 相互作用，抑制它们与LATERAL ORGAN BOUNDARY DOMAIN16 ( LBD16)位点的结合) 抑制其在中柱中柱中的表达。SHY2 还与内皮层中的 ARF7 和 ARF19 相互作用，增强 DA3 对 ARF7 和 ARF19 的抑制作用，从而调节中柱鞘中的LBD16表达。总的来说，我们的研究结果表明，DA3 与 SHY2、ARF7 和 ARF19 协同作用，协调中柱周和内皮中的生长素信号，从而控制拟南芥中 LR 的启动。