Department of Bioenergy Science and Technology, Chonnam National University, Gwangju 500-757, Korea.
Department of Biological Sciences, Sungkyunkwan University, Suwon, Korea.
Plant Cell Physiol. 2017 Dec 1;58(12):2190-2201. doi: 10.1093/pcp/pcx153.
The LATERAL ORGAN BOUNDARIES (LOB) DOMAIN/ASYMMETRIC LEAVES2-LIKE (LBD/ASL) gene family members play key roles in diverse aspects of plant development. Previous studies have shown that LBD16, 18, 29 and 33 are critical for integrating the plant hormone auxin to control lateral root development in Arabidopsis thaliana. In the present study, we show that LBD14 is expressed exclusively in the root where it promotes lateral root (LR) emergence. Repression of LBD14 expression by ABA correlates with the inhibitory effects of ABA on LR emergence. Transient gene expression assays with Arabidopsis protoplasts demonstrated that LBD14 is a nuclear-localized transcriptional activator. The knock-down of LBD14 expression by RNA interference (RNAi) resulted in reduced LR formation by delaying both LR primordium development and LR emergence, whereas overexpression of LBD14 in Arabidopsis enhances LR formation. We show that ABA (but not other plant hormones such as auxin, brassinosteroids and cytokinin) specifically down-regulated β-glucuronidase (GUS) expression under the control of the LBD14 promoter in transgenic Arabidopsis during LR development from initiation to emergence and endogenous LBD14 transcript levels in the root. Moreover, RNAi of LBD14 enhanced the LR suppression in response to ABA, whereas LBD14 overexpression did not alter the ABA-mediated suppression of LR formation. Taken together, these results suggest that LBD14 promoting LR formation is one of the critical factors regulated by ABA to inhibit LR growth, contributing to the regulation of the Arabidopsis root system architecture in response to ABA.
侧生器官边界（LOB）域/不对称叶 2 样（LBD/ASL）基因家族成员在植物发育的多个方面发挥着关键作用。先前的研究表明，LBD16、18、29 和 33 对于整合植物激素生长素以控制拟南芥侧根发育至关重要。在本研究中，我们表明 LBD14 仅在根中表达，在根中它促进侧根（LR）的出现。ABA 对 LBD14 表达的抑制与 ABA 对 LR 出现的抑制作用相关。用拟南芥原生质体进行的瞬时基因表达测定表明，LBD14 是一种核定位的转录激活剂。通过 RNA 干扰（RNAi）抑制 LBD14 表达会导致 LR 形成减少，从而延迟 LR 原基发育和 LR 出现，而在拟南芥中过表达 LBD14 则增强 LR 形成。我们表明，ABA（而不是其他植物激素，如生长素、油菜素内酯和细胞分裂素）在 LR 从起始到出现的发育过程中特异性下调 LBD14 启动子控制的转基因拟南芥中的β-葡萄糖醛酸酶（GUS）表达和根中的内源性 LBD14 转录本水平。此外，LBD14 的 RNAi 增强了对 ABA 的 LR 抑制反应，而 LBD14 的过表达并未改变 ABA 介导的 LR 形成抑制。综上所述，这些结果表明，LBD14 促进 LR 形成是 ABA 抑制 LR 生长的关键调节因子之一，有助于调节拟南芥根系结构对 ABA 的反应。
