Arabidopsis ABCG14 forms a homodimeric transporter for multiple cytokinins and mediates long-distance transport of isopentenyladenine-type cytokinins

Jiangzhe Zhao; Xiaojuan Deng; Jiayun Qian; Ting Liu; Min Ju; Juan Li; Qin Yang; Xiaoxian Zhu; Weiqiang Li; Chang-Jun Liu; Zhigang Jin; Kewei Zhang

doi:10.1016/j.xplc.2022.100468

Arabidopsis ABCG14 forms a homodimeric transporter for multiple cytokinins and mediates long-distance transport of isopentenyladenine-type cytokinins

Plant Commun. 2023 Mar 13;4(2):100468. doi: 10.1016/j.xplc.2022.100468. Epub 2022 Oct 28.

Authors

Jiangzhe Zhao¹, Xiaojuan Deng¹, Jiayun Qian¹, Ting Liu¹, Min Ju¹, Juan Li¹, Qin Yang¹, Xiaoxian Zhu¹, Weiqiang Li², Chang-Jun Liu³, Zhigang Jin¹, Kewei Zhang⁴

Affiliations

¹ Institute of Plant Stress Adaptation and Genetic Enhancement, Zhejiang Provincial Key Laboratory of Biotechnology on Specialty Economic Plants, College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua, Zhejiang 321004, P.R. China.
² Key Laboratory of Mollisols Agroecology, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, No. 4888 Shengbei Street, Changchun 130102, China.
³ Biology Department, Brookhaven National Laboratory, Upton, NY 11973, USA.
⁴ Institute of Plant Stress Adaptation and Genetic Enhancement, Zhejiang Provincial Key Laboratory of Biotechnology on Specialty Economic Plants, College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua, Zhejiang 321004, P.R. China. Electronic address: kwzhang@zjnu.edu.cn.

Abstract

Cytokinins (CKs), primarily trans-zeatin (tZ) and isopentenyladenine (iP) types, play critical roles in plant growth, development, and various stress responses. Long-distance transport of tZ-type CKs meidated by Arabidopsis ATP-binding cassette transporter subfamily G14 (AtABCG14) has been well studied; however, less is known about the biochemical properties of AtABCG14 and its transporter activity toward iP-type CKs. Here we reveal the biochemical properties of AtABCG14 and provide evidence that it is also required for long-distance transport of iP-type CKs. AtABCG14 formed homodimers in human (Homo sapiens) HEK293T, tobacco (Nicotiana tabacum), and Arabidopsis cells. Transporter activity assays of AtABCG14 in Arabidopsis, tobacco, and yeast (Saccharomyces cerevisiae) showed that AtABCG14 may directly transport multiple CKs, including iP- and tZ-type species. AtABCG14 expression was induced by iP in a tZ-type CK-deficient double mutant (cypDM) of CYP735A1 and CYP735A2. The atabcg14 cypDM triple mutant exhibited stronger CK-deficiency phenotypes than cypDM. Hormone profiling, reciprocal grafting, and ²H₆-iP isotope tracer experiments showed that root-to-shoot and shoot-to-root long-distance transport of iP-type CKs were suppressed in atabcg14 cypDM and atabcg14. These results suggest that AtABCG14 participates in three steps of the circular long-distance transport of iP-type CKs: xylem loading in the root for shootward transport, phloem unloading in the shoot for shoot distribution, and phloem unloading in the root for root distribution. We found that AtABCG14 displays transporter activity toward multiple CK species and revealed its versatile roles in circular long-distance transport of iP-type CKs. These findings provide new insights into the transport mechanisms of CKs and other plant hormones.

Keywords: circular transport; half-size ABC transporter; homodimer; isopentenyladenine-type cytokinins; long-distance transport.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Arabidopsis Proteins* / genetics
Arabidopsis Proteins* / metabolism
Arabidopsis* / metabolism
Cytokinins
HEK293 Cells
Humans
Membrane Transport Proteins / metabolism

Substances

Arabidopsis Proteins
Cytokinins
Membrane Transport Proteins
N(6)-(delta(2)-isopentenyl)adenine
ABCG14 protein, Arabidopsis