A ROP GTPase-dependent auxin signaling pathway regulates the subcellular distribution of PIN2 in Arabidopsis roots.
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, 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. SPK1 belongs to the conserved DHR2-Dock family of Rho guanine nucleotide exchange factors. 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.
State Key Laboratory of Plant Physiology and Biochemistry, Department of Plant Sciences, College of Biological Sciences, China Agricultural University, Beijing 100193, China.
Deshu
D
Lin
Shingo
S
Nagawa
Jisheng
J
Chen
Lingyan
L
Cao
Xu
X
Chen
Tongda
T
Xu
Hongjiang
H
Li
Pankaj
P
Dhonukshe
Chizuko
C
Yamamuro
Jiří
J
Friml
Ben
B
Scheres
Ying
Y
Fu
Zhenbiao
Z
Yang
D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D007210:Indoleacetic Acids / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D020559:Monomeric GTP-Binding Proteins / Q000378:metabolism*; D009024:Morphogenesis; D018517:Plant Roots / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D015398:Signal Transduction
D029681:Arabidopsis Proteins; D019204:GTP-Binding Proteins; D007210:Indoleacetic Acids; D008869:Microtubule-Associated Proteins; D020559:Monomeric GTP-Binding Proteins; C117013:AT5G57090 protein, Arabidopsis; C547530:RIC1 protein, Arabidopsis; C518506:ROP6 protein, Arabidopsis; C455512:SPIKE1 protein, Arabidopsis