Hormone Autotrophic Growth and Differentiation Identifies Mutant Lines of Arabidopsis with Altered Cytokinin and Auxin Content or Signaling

• Published in: Plant physiology (Bethesda) 2000-03, Vol.122 (3), p.721-729
• Main Authors: Frank, Markus, Hans-Michael Rupp, Prinsen, Els, Motyka, Václav, Van Onckelen, Harry, Schmülling, Thomas
• Format: Article
• Language: English
• Subjects: Arabidopsis; Arabidopsis - genetics; Arabidopsis - growth & development; Arabidopsis - metabolism; Auxins; Biological and medical sciences; Callus; cdc2 gene; Cell Cycle - genetics; Cell differentiation; Cell physiology; CKI1 gene; cycD3 gene; Cytokinins; Cytokinins - metabolism; Fundamental and applied biological sciences. Psychology; Genes; Growth and Development; Hormones; IAA1 gene; IAA2 gene; Indoleacetic Acids - metabolism; KNAT1 gene; Messenger RNA; Mutation; Oxidases; Phenotype; Plant Growth Regulators - metabolism; Plant physiology and development; Plants; RNA, Messenger - genetics; RNA, Messenger - metabolism; RNA, Plant - genetics; RNA, Plant - metabolism; Seedlings; Signal Transduction; Space life sciences; STM gene; Tumors
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.122.3.721

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.