A ROP GTPase-Dependent Auxin Signaling Pathway Regulates the Subcellular Distribution of PIN2 in Arabidopsis Roots

• Published in: Current biology 2012-07, Vol.22 (14), p.1319-1325
• Main Authors: Lin, Deshu, Nagawa, Shingo, Chen, Jisheng, Cao, Lingyan, Chen, Xu, Xu, Tongda, Li, Hongjiang, Dhonukshe, Pankaj, Yamamuro, Chizuko, Friml, Jiří, Scheres, Ben, Fu, Ying, Yang, Zhenbiao
• Format: Article
• Language: English
• Subjects: Arabidopsis; Arabidopsis - genetics; Arabidopsis - growth & development; Arabidopsis - metabolism; Arabidopsis Proteins - metabolism; auxins; endocytosis; genes; gravitropism; GTP-Binding Proteins - metabolism; guanine nucleotides; guanosinetriphosphatase; Indoleacetic Acids - metabolism; Microtubule-Associated Proteins - metabolism; Monomeric GTP-Binding Proteins - metabolism; Morphogenesis; mutagenesis; Plant Roots - genetics; Plant Roots - growth & development; Plant Roots - metabolism; plasma membrane; roots; Signal Transduction
• ISSN: 0960-9822; 1879-0445
• DOI: 10.1016/j.cub.2012.05.019

PIN-FORMED (PIN) protein-mediated auxin polar transport is critically important for development, pattern formation, and morphogenesis in plants. Auxin has been implicated in the regulation of polar auxin transport by inhibiting PIN endocytosis [1, 2], but how auxin regulates this process is poorly understood. Our genetic screen identified the Arabidopsis SPIKE1 (SPK1) gene whose loss-of-function mutations increased lateral root density and retarded gravitropic responses, as do pin2 knockout mutations [3]. SPK1 belongs to the conserved DHR2-Dock family of Rho guanine nucleotide exchange factors [4–6]. The spk1 mutations induced PIN2 internalization that was not suppressed by auxin, as did the loss-of-function mutations for Rho-like GTPase from Plants 6 (ROP6)-GTPase or its effector RIC1. Furthermore, SPK1 was required for auxin induction of ROP6 activation. Our results have established a Rho GTPase-based auxin signaling pathway that maintains PIN2 polar distribution to the plasma membrane via inhibition of its internalization in Arabidopsis roots. Our findings provide new insights into signaling mechanisms that underlie the regulation of the dynamic trafficking of PINs required for long-distance auxin transport and that link auxin signaling to PIN-mediated pattern formation and morphogenesis. ► The SPK1 RopGEF promotes PIN2 polar distribution to the plasma membrane ► SPK1 acts upstream of ROP6/RIC1 pathway in the regulation of PIN2 internalization ► SPK1 is required for auxin-mediated ROP6 activation ► ROP6/RIC1-mediated inhibition of PIN2 internalization involves actin