LBD18 acts as a transcriptional activator that directly binds to the EXPANSIN14 promoter in promoting lateral root emergence of Arabidopsis
LBD18 acts as a transcriptional activator that directly binds to the EXPANSIN14 promoter in promoting lateral root emergence of Arabidopsis
复制标题
DOI：
10.1111/tpj.12013
复制
发表时间：
2013-01-01
期刊：
影响因子：
7.2
通讯作者：
Kim, Jungmook
中科院分区：
文献类型：
--
作者：
Lee, Han Woo;Kim, Min-Jung;Kim, Jungmook
侧根形成是植物激素生长素控制下的发育过程，是根构型的主要决定因素，并定义了植物获取营养和水分的能力。LBD/ASL蛋白在植物侧根形成过程中起重要作用。然而，其下游成分和信号传导机制在很大程度上是未知的。在这里，我们表明，生长素响应LBD 18/ASL 20作为一个特定的DNA结合转录激活因子，直接调节EXPANSIN 14（EXP 14），一个基因编码的细胞壁疏松因子，促进侧根出现在拟南芥。我们发现LBD 18在酵母和拟南芥原生质体中都具有转录激活功能。我们通过微阵列分析分离了推定的LBD 18靶基因，并将EXP 14鉴定为LBD 18的直接靶标。地塞米松诱导的表达LBD 18下的CaMV 35 S启动子在转基因拟南芥中的原基和覆盖组织中的GUS融合到EXP 14启动子的表达增强。相反，在lbd 18突变体背景中，在EXP 14启动子下的GUS表达在相同组织中显著降低。使用多种分子技术的实验表明，LBD 18通过在体外和体内直接结合到特异性启动子元件来激活EXP 14。EXP 14在拟南芥中的过表达导致出现侧根的刺激，但不是原基，而EXP 14功能丧失的植物减少了生长素刺激的侧根形成。这项研究揭示了LBD 18作为一种特异性DNA结合转录因子的分子功能，它通过直接结合其启动子来激活EXP 14的表达。
Lateral root formation, a developmental process under the control of the plant hormone auxin, is a major determinant of root architecture, and defines the ability of a plant to acquire nutrients and water. The LATERAL ORGAN BOUNDARIES DOMAIN/ASYMMETRIC LEAVES2-LIKE (LBD/ASL) proteins play an important role in the lateral organ development of plants, including lateral root formation. However, their downstream components and signalling mechanisms are largely unknown. Here, we show that auxin-responsive LBD18/ASL20 acts as a specific DNA-binding transcriptional activator that directly regulates EXPANSIN14 (EXP14), a gene encoding a cell wall-loosening factor that promotes lateral root emergence in Arabidopsis thaliana. We showed that LBD18 possesses transcription-activating function in both yeast and Arabidopsis protoplasts. We isolated putative LBD18 target genes by microarray analysis, and identified EXP14 as a direct target of LBD18. Dexamethasone-induced expression of LBD18 under the CaMV 35S promoter in transgenic Arabidopsis resulted in enhanced expression of GUS fused to the EXP14 promoter in primordium and overlaying tissues. In contrast, GUS expression under the EXP14 promoter in the lbd18 mutant background was significantly reduced in the same tissues. Experiments using a variety of molecular techniques demonstrated that LBD18 activates EXP14 by directly binding to a specific promoter element in vitro and in vivo. Overexpression of EXP14 in Arabidopsis resulted in the stimulation of emerged lateral roots, but not primordia, whereas EXP14 loss-of-function plants had reduced auxin-stimulated lateral root formation. This study revealed the molecular function of LBD18 as a specific DNA-binding transcription factor that activates EXP14 expression by directly binding to its promoter.