Abstract\n\n Trans-zeatin (tZ)-type cytokinins (CKs) are predominantly synthesized in roots, transported to shoot via xylem, and coordinate diverse physiological processes in aerial organs. Within this mechanism, the regulation of CK biosynthesis by nitrate signaling via NIN-like protein 7 as well as the loading of tZ-type CKs into xylem by ATP-binding cassette transporter G14 have been well studied. However, the roles of other components remain unclear. Here, we show that CK perception and degradation in roots, as mediated by Arabidopsis histidine kinase 3 (AHK3) and CK oxidase\/dehydrogenase 4 (CKX4), modulate root-to-shoot tZ-type cytokinin transport in response to nitrate. Grafting experiments demonstrated that root-specific AHK3 deficiency systemically increased leaf blade area through long-distance signals of root-derived tZ-type CK, perceived by shoot-expressed AHK3. Transcriptome and hormonome analyses revealed that root-specific AHK3 deficiency reduced CKX4 expression in roots, elevating tZ-type CK levels in roots and xylem sap and thereby enhancing leaf CK response. Transfer experiments manipulating root nitrate levels showed that root-specific AHK3 deficiency promoted leaf blade area in a manner dependent on both nitrate and root-derived tZ-type CK signaling. Moreover, both nitrate signals and root-expressed AHK3 are required for maximal CKX4 induction in roots, and root-specific CKX4 deficiency enhanced leaf blade area in a nitrate-dependent manner. These findings reveal a novel mechanism in which an AHK3\u2013CKX4 module governs xylem transport of tZ-type CKs, fine-tuning leaf size according to root nitrate status.<\/p>","protected":false},"excerpt":{"rendered":"Kota Monden, Takamasa Suzuki, Mikiko Kojima, Yumiko Takebayashi, Takehiro Kamiya, Takatoshi Kiba, Hitoshi Saka […]","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5],"tags":[],"class_list":["post-3538","post","type-post","status-publish","format-standard","hentry","category-article"],"_links":{"self":[{"href":"https:\/\/biochemistry.isc.chubu.ac.jp\/labo\/suzuki\/wp-json\/wp\/v2\/posts\/3538","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/biochemistry.isc.chubu.ac.jp\/labo\/suzuki\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/biochemistry.isc.chubu.ac.jp\/labo\/suzuki\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/biochemistry.isc.chubu.ac.jp\/labo\/suzuki\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/biochemistry.isc.chubu.ac.jp\/labo\/suzuki\/wp-json\/wp\/v2\/comments?post=3538"}],"version-history":[{"count":0,"href":"https:\/\/biochemistry.isc.chubu.ac.jp\/labo\/suzuki\/wp-json\/wp\/v2\/posts\/3538\/revisions"}],"wp:attachment":[{"href":"https:\/\/biochemistry.isc.chubu.ac.jp\/labo\/suzuki\/wp-json\/wp\/v2\/media?parent=3538"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/biochemistry.isc.chubu.ac.jp\/labo\/suzuki\/wp-json\/wp\/v2\/categories?post=3538"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/biochemistry.isc.chubu.ac.jp\/labo\/suzuki\/wp-json\/wp\/v2\/tags?post=3538"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}