1. Phloem unloading via the apoplastic pathway is essential for shoot distribution of root-synthesized cytokinins
- Author
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Xiaojuan Deng, Dai Yangshuo, Engao Zhu, Bingli Ding, Shi Xiao, Lu Wang, Jiangzhe Zhao, Penghong Zhang, Kewei Zhang, Cankui Zhang, Chang-Jun Liu, and Mengyuan Zhang
- Subjects
0106 biological sciences ,Cytokinins ,Physiology ,Arabidopsis ,Plant Science ,Phloem ,Plant Roots ,01 natural sciences ,03 medical and health sciences ,chemistry.chemical_compound ,Genetics ,Arabidopsis thaliana ,heterocyclic compounds ,Research Articles ,030304 developmental biology ,0303 health sciences ,biology ,fungi ,food and beverages ,Xylem ,Biological Transport ,biology.organism_classification ,Apoplast ,Cell biology ,chemistry ,Cytokinin ,Shoot ,Rootstock ,Plant Shoots ,Signal Transduction ,010606 plant biology & botany - Abstract
Root-synthesized cytokinins are transported to the shoot and regulate the growth, development, and stress responses of aerial tissues. Previous studies have demonstrated that Arabidopsis (Arabidopsis thaliana) ATP binding cassette (ABC) transporter G family member 14 (AtABCG14) participates in xylem loading of root-synthesized cytokinins. However, the mechanism by which these root-derived cytokinins are distributed in the shoot remains unclear. Here, we revealed that AtABCG14-mediated phloem unloading through the apoplastic pathway is required for the appropriate shoot distribution of root-synthesized cytokinins in Arabidopsis. Wild-type rootstocks grafted to atabcg14 scions successfully restored trans-zeatin xylem loading. However, only low levels of root-synthesized cytokinins and induced shoot signaling were rescued. Reciprocal grafting and tissue-specific genetic complementation demonstrated that AtABCG14 disruption in the shoot considerably increased the retention of root-synthesized cytokinins in the phloem and substantially impaired their distribution in the leaf apoplast. The translocation of root-synthesized cytokinins from the xylem to the phloem and the subsequent unloading from the phloem is required for the shoot distribution and long-distance shootward transport of root-synthesized cytokinins. This study revealed a mechanism by which the phloem regulates systemic signaling of xylem-mediated transport of root-synthesized cytokinins from the root to the shoot.
- Published
- 2021