title: Hormone autotrophic growth and differentiation identifies mutant lines of Arabidopsis with altered cytokinin and auxin content or signaling.
abstract: We describe mutant tissue lines of Arabidopsis that are able to grow in vitro as callus on hormone-free medium. The 14 lines presented here show different hormone autotrophic differentiation behaviors that can be classified into three categories: (a) forming roots (rooty callus), (b) forming shoots or shoot-like structures (shooty callus), or (c) growing without organ formation (callus). Three fast-growing lines showed altered steady-state mRNA levels of the Cdc2 and CycD3 cell cycle genes. Three of the six rooty callus lines contained about 20- to 30-fold higher levels of auxins than wild-type callus. These and two other lines with normal auxin content showed an increased steady-state level of IAA1 and IAA2 transcripts in the absence of exogenous auxin. Five of the six shooty callus lines had increased steady-state mRNA levels of the CKI1 gene and/or of the homeobox genes KNAT1 and STM, suggesting that the phenotype is linked to altered cytokinin signaling. Also, one cytokinin-overproducing line with only 5% of wild-type cytokinin oxidase activity was identified. These results indicate that screening for hormone-autonomous growth identifies mutants with altered hormone content or signaling.
authors.affiliation: Universität Tübingen, Center for Plant Molecular Biology (ZMBP), Allgemeine Genetik, Auf der Morgenstelle 28, D-72076 Tübingen, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Frank
authors.forename: H M
authors.initials: HM
authors.lastname: Rupp
authors.forename: E
authors.initials: E
authors.lastname: Prinsen
authors.forename: V
authors.initials: V
authors.lastname: Motyka
authors.forename: H
authors.initials: H
authors.lastname: Van Onckelen
authors.forename: T
authors.initials: T
authors.lastname: Schmülling
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D002453:Cell Cycle / Q000235:genetics; D003583:Cytokinins / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism; D009154:Mutation; D010641:Phenotype; D010937:Plant Growth Regulators / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D003583:Cytokinins; D007210:Indoleacetic Acids; D010937:Plant Growth Regulators; D012333:RNA, Messenger; D018749:RNA, Plant