J Integr Plant Biol ›› 2017, Vol. 59 ›› Issue (1): 30-43.DOI: 10.1111/jipb.12506

Special Issue: Cell Biology and Functions

• Cell and Developmental Biology • Previous Articles     Next Articles

ARF2 coordinates with PLETHORAs and PINs to orchestrate ABA-mediated root meristem activity in Arabidopsis

Sujittra Promchuea1, Yujuan Zhu1, Zhizhong Chen1, Jing Zhang1 and Zhizhong Gong1,2*   

  1. 1State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
    2National Center for Plant Gene Research, Beijing 100193, China
  • Received:2016-10-07 Accepted:2016-11-01 Published:2016-11-07
  • About author:*Correspondence: E-mail: Zhizhong Gong (gongzz@cau.edu.cn)

Abstract:

Multiple hormones, including abscisic acid (ABA) and auxin, regulate cell division and differentiation of Arabidopsis root meristems. AUXIN RESPONSE FACTOR 2 (ARF2) functions as a negative regulator of ABA responses, as seed germination and primary root growth of arf2 mutants are hypersensitive to ABA. In this study, we found that ABA treatment reduced the expression levels of the PIN-FORMEDs (PIN) auxin efflux carriers, PIN1, PIN3, PIN4, and PIN7, to a greater extent in the root meristems of arf2-101 mutant than in the wild type. Also, arf2-101 pin1 and arf2-101 pin4 double mutants show less ABA-induced inhibition of root meristem activity than the arf2-101 mutants. Furthermore, ARF2 positively mediates the transcripts of transcription factor PLETHORA 1 (PLT1) gene but negatively mediates PLT2 at protein level in root meristems. Using a dexamethasone (DEX)-inducible transgenic line, Pro35S:PLT2-GR, we showed that PLT2 greatly promotes cell division and completely inhibits cell differentiation in root meristems of the arf2-101 mutant once PLT2 is induced by DEX, which can be partially reversed by ABA treatment, suggesting that ABA regulates root meristem activity in both ARF2-dependent and independent pathways. Our results uncover a complex regulatory architecture in which ARF2 coordinates with PLTs and PINs to orchestrate ABA-mediated regulation of root meristem activity in Arabidopsis.

PLETHORA 1 (PLT1) and PLT2 are two key transcription factors that regulate the root apical meristem. It is found that AUXIN RESPONSE FACTOR2 (ARF2) negatively mediates stability of PLT2 protein. Conditional overexpression of PLT2 largely promotes cell division and completely inhibits cell differentiation in root meristems of the arf2 mutant.

Key words: Abscisic acid, Arabidopsis, auxin, AUXIN RESPONSE FACTOR, PIN-FORMED, PLETHORA, root meristem

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