title: The Mobile bypass Signal Arrests Shoot Growth by Disrupting Shoot Apical Meristem Maintenance, Cytokinin Signaling, and WUS Transcription Factor Expression.
abstract: The bypass1 (bps1) mutant of Arabidopsis (Arabidopsis thaliana) produces a root-sourced compound (the bps signal) that moves to the shoot and is sufficient to arrest growth of a wild-type shoot; however, the mechanism of growth arrest is not understood. Here, we show that the earliest shoot defect arises during germination and is a failure of bps1 mutants to maintain their shoot apical meristem (SAM). This finding suggested that the bps signal might affect expression or function of SAM regulatory genes, and we found WUSCHEL (WUS) expression to be repressed in bps1 mutants. Repression appears to arise from the mobile bps signal, as the bps1 root was sufficient to rapidly down-regulate WUS expression in wild-type shoots. Normally, WUS is regulated by a balance between positive regulation by cytokinin (CK) and negative regulation by CLAVATA (CLV). In bps1, repression of WUS was independent of CLV, and, instead, the bps signal down-regulates CK responses. Cytokinin treatment of bps1 mutants restored both WUS expression and activity, but only in the rib meristem. How the bps signal down-regulates CK remains unknown, though the bps signal was sufficient to repress expression of one CK receptor (AHK4) and one response regulator (AHP6). Together, these data suggest that the bps signal pathway has the potential for long-distance regulation through modification of CK signaling and altering gene expression.
authors.affiliation: Department of Biology, University of Utah, Salt Lake City, Utah 84112.
authors.forename: Dong-Keun
authors.identifier: 0000-0002-4952-8004
authors.initials: DK
authors.lastname: Lee
authors.affiliation: Department of Biology, University of Utah, Salt Lake City, Utah 84112.
authors.forename: David L
authors.initials: DL
authors.lastname: Parrott
authors.affiliation: Department of Biology, University of Utah, Salt Lake City, Utah 84112.
authors.forename: Emma
authors.initials: E
authors.lastname: Adhikari
authors.affiliation: Department of Biology, University of Utah, Salt Lake City, Utah 84112.
authors.forename: Nisa
authors.initials: N
authors.lastname: Fraser
authors.affiliation: Department of Biology, University of Utah, Salt Lake City, Utah 84112 sieburth@biology.utah.edu.
authors.forename: Leslie E
authors.identifier: 0000-0001-6691-2000
authors.initials: LE
authors.lastname: Sieburth
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001593:Benzyl Compounds / Q000494:pharmacology; D003583:Cytokinins / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D018506:Gene Expression Regulation, Plant; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D018519:Meristem / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D018520:Plant Shoots / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D030821:Plants, Genetically Modified; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011687:Purines / Q000494:pharmacology; D015398:Signal Transduction / Q000235:genetics
chemical_list: D029681:Arabidopsis Proteins; C548135:BYPASS1 protein, Arabidopsis; D001593:Benzyl Compounds; D003583:Cytokinins; D018398:Homeodomain Proteins; D011687:Purines; C116421:WUSCHEL protein, Arabidopsis; C118166:CLV1 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases; C480551:benzylaminopurine