669 / 2019-04-30 15:38:46

AtABCG14 synchronizes the xylem loading and unloading of the root-derived cytokinins in their acropetal translocation

ABC transporter; cytokinin; long-distance transport;

全体主题 > Hormones

The root-to-shoot translocation of a substance via the xylem system in planta includes the xylem loading in the root, transport in the vessels and unloading in the shoot. Cytokinins（CKs）are one kind of the most important phytohormones essential for plant growth, development and stress responses. The root-derived CKs are transported to the root via a long-distance translocation in the xylem system thus are moved from the source cells in the root to the sink cells in the shoot. Arabidopsis ATP binding cassette G14 (AtABCG14) was previously proven to be the transporter responsible for xylem loading of trans-zeatin type CKs in the root. However, the unloading process of the root-derived CKs in the aerial tissue of the plants remains unknown. In the present study, we found the AtABCG14 expressed in the parenchyma cells in the midribs of the aerial tissues despite its expression in the root stele of Arabidopsis. The grafted plants of atabcg14 as scion and WT as the root-stock successfully restored the xylem loading of 14C or 13C labeled trans-zeatin but did not recover the CK deficient phenotype of atabcg14 to WT. The disruption of AtABCG14 in the aerial tissue represses the release of the root-synthesized CKs from the leaf midrib. Our finding provides a model how plant synchronizes the CK acrepedal transport, the xylem loading in the root and unloading in the shoot, using the same transporter AtABCG14.