Okushima Yoko, Fukaki Hidehiro, Onoda Makoto, Theologis Athanasios, Tasaka Masao
Nara Institute of Science and Technology, Graduate School of Biological Sciences, Takayama 8916-5, Ikoma, Nara 630-0101, Japan.
Plant Cell. 2007 Jan;19(1):118-30. doi: 10.1105/tpc.106.047761. Epub 2007 Jan 26.
Lateral root formation in Arabidopsis thaliana is regulated by two related AUXIN RESPONSE FACTORs, ARF7 and ARF19, which are transcriptional activators of early auxin response genes. The arf7 arf19 double knockout mutant is severely impaired in lateral root formation. Target-gene analysis in arf7 arf19 transgenic plants harboring inducible forms of ARF7 and ARF19 revealed that ARF7 and ARF19 directly regulate the auxin-mediated transcription of LATERAL ORGAN BOUNDARIES-DOMAIN16/ASYMMETRIC LEAVES2-LIKE18 (LBD16/ASL18) and/or LBD29/ASL16 in roots. Overexpression of LBD16/ASL18 and LBD29/ASL16 induces lateral root formation in the absence of ARF7 and ARF19. These LBD/ASL proteins are localized in the nucleus, and dominant repression of LBD16/ASL18 activity inhibits lateral root formation and auxin-mediated gene expression, strongly suggesting that these LBD/ASLs function downstream of ARF7- and ARF19-dependent auxin signaling in lateral root formation. Our results reveal that ARFs regulate lateral root formation via direct activation of LBD/ASLs in Arabidopsis.
拟南芥的侧根形成受两个相关的生长素响应因子ARF7和ARF19调控，它们是早期生长素响应基因的转录激活因子。arf7 arf19双敲除突变体在侧根形成方面严重受损。对携带可诱导形式的ARF7和ARF19的arf7 arf19转基因植物进行靶基因分析发现，ARF7和ARF19直接调控根中生长素介导的侧器官边界域16/不对称叶2样18（LBD16/ASL18）和/或LBD29/ASL16的转录。在没有ARF7和ARF19的情况下，LBD16/ASL18和LBD29/ASL16的过表达诱导侧根形成。这些LBD/ASL蛋白定位于细胞核，LBD16/ASL18活性的显性抑制抑制侧根形成和生长素介导的基因表达，这强烈表明这些LBD/ASL在侧根形成中在ARF7和ARF19依赖性生长素信号传导的下游发挥作用。我们的结果表明，在拟南芥中ARF通过直接激活LBD/ASL来调控侧根形成。
