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The HDZip class I genes ATHB5, -6 and -16 act redundantly to mediate light effects on hypocotyl elongation
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Physiological Botany.
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(English)Manuscript (Other (popular science, discussion, etc.))
Identifiers
URN: urn:nbn:se:uu:diva-92030OAI: oai:DiVA.org:uu-92030DiVA: diva2:164970
Available from: 2004-09-02 Created: 2004-09-02 Last updated: 2010-01-14Bibliographically approved
In thesis
1. The HDZip Class I Transcription Factors in Arabidopsis thaliana: Characterisation of HDZip Genes Involved in the Mediation of Environmental Signals
Open this publication in new window or tab >>The HDZip Class I Transcription Factors in Arabidopsis thaliana: Characterisation of HDZip Genes Involved in the Mediation of Environmental Signals
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Homeodomain leucine zipper (HDZip) proteins constitute a large family of transcription factors characterised by the presence of a DNA-binding homeodomain and an adjacent leucine zipper motif, which mediates protein-dimer formation. The HDZip genes of Arabidopsis have been divided into four classes, HDZip I-IV. This thesis describes the characterisation and phylogeny of the class I HDZip genes and focuses on the expression and function of four HDZip I genes, ATHB5, -6, -7 and -16.

The phylogenetic analyses of the 17 HDZip I sequences defined six subclasses, supported by the intron patterning and the traced duplication history of the genes. The members within each subclass showed diversification in expression, suggesting that the cis regulatory regions of the closely related genes have undergone evolutionary changes. However, similarities in the gene expression patterns between genes also exist and external factors like the availability of water and quality of light directs the expression of a subset of HDZip I genes. Expression analyses revealed that the plant hormone abscisic acid (ABA) is involved as a systemic signal for the salt or osmoticum induced ATHB7 expression, whereas light signals mediated through the blue light photoreceptors was found to direct the expression of ATHB6.

Phenotypic analyses of plants with altered levels of ATHB6 or ATHB16 suggested that these paralogous genes encode proteins with very similar functions. ATHB16 was shown to act as a negative regulator of leaf cell expansion, as a suppressor of the flowering time sensitivity to photoperiod and as a positive regulator of blue light dependent inhibition of hypocotyl growth. A similar role for ATHB6 in the regulation of hypocotyl elongation was recorded. Further, analyses of multiple loss-of-function plants demonstrated that ATHB5, -6 and -16 function at least in part redundantly in mediating light effects on hypocotyl elongation.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2004. 53 p.
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 1003
Keyword
Plant physiology, Växtfysiologi
National Category
Botany
Identifiers
urn:nbn:se:uu:diva-4507 (URN)91-554-6018-6 (ISBN)
Public defence
2004-09-24, Lecture hall, room 3041, Department of Physiological Botany, Villavägen 6, Uppsala, 13:00 (English)
Opponent
Supervisors
Available from: 2004-09-02 Created: 2004-09-02 Last updated: 2009-04-02Bibliographically approved

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