Department of Biology, Graduate School of Science, Kobe University, 1-1 Rokkodai, Kobe, 657-8501, Japan.
Graduate School of Science and Technology, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, 630-0192, Japan.
New Phytol. 2019 Oct;224(2):749-760. doi: 10.1111/nph.16065. Epub 2019 Aug 10.
Lateral root (LR) formation in Arabidopsis thaliana is initiated by asymmetric division of founder cells, followed by coordinated cell proliferation and differentiation for patterning new primordia. The sequential developmental processes of LR formation are triggered by a localized auxin response. LATERAL ORGAN BOUNDARIES-DOMAIN 16 (LBD16), an auxin-inducible transcription factor, is one of the key regulators linking auxin response in LR founder cells to LR initiation. We identified key genes for LR formation that are activated by LBD16 in an auxin-dependent manner. LBD16 targets identified include the transcription factor gene PUCHI, which is required for LR primordium patterning. We demonstrate that LBD16 activity is required for the auxin-inducible expression of PUCHI. We show that PUCHI expression is initiated after the first round of asymmetric cell division of LR founder cells and that premature induction of PUCHI during the preinitiation phase disrupts LR primordium formation. Our results indicate that LR initiation requires the sequential induction of transcription factors LBD16 and PUCHI.
拟南芥侧根（LR）的形成是由起始细胞的不对称分裂启动的，随后通过协调细胞增殖和分化来形成新的原基。LR 形成的顺序发育过程是由局部生长素响应触发的。生长素诱导转录因子 LATERAL ORGAN BOUNDARIES-DOMAIN 16（LBD16）是将 LR 起始细胞中的生长素响应与 LR 起始联系起来的关键调节因子之一。我们确定了关键的 LR 形成基因，这些基因在生长素依赖性方式下被 LBD16 激活。鉴定出的 LBD16 靶标包括转录因子基因 PUCHI，该基因对于 LR 原基的模式形成是必需的。我们证明 LBD16 活性对于生长素诱导的 PUCHI 表达是必需的。我们表明，PUCHI 的表达是在 LR 起始细胞的第一轮不对称细胞分裂之后开始的，并且在起始前阶段过早诱导 PUCHI 会破坏 LR 原基的形成。我们的结果表明，LR 起始需要转录因子 LBD16 和 PUCHI 的顺序诱导。
