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The RY/Sph element mediates transcriptional repression of MAT genes from late maturation to early seedling growth
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
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2009 (English)In: New Phytologist, ISSN 0028-646X, E-ISSN 1469-8137, Vol. 184, no 3, 552-565 p.Article in journal (Refereed) Published
Abstract [en]

P>In orthodox seeds, the transcriptional activator ABI3 regulates two   major stages in embryo maturation: a mid-maturation (MAT) stage leading   to accumulation of storage compounds, and a late maturation (LEA) stage   leading to quiescence and desiccation tolerance. Our aim was to   elucidate mechanisms for transcriptional shutdown of MAT genes during   late maturation, to better understand phase transition between MAT and   LEA stages.   Using transgenic and transient approaches in Nicotiana, we examined   activities of two ABI3-dependent reporter genes driven by multimeric RY   and abscisic acid response elements (ABREs) from a Brassica napus napin   gene, termed RY and ABRE, where the RY reporter requires ABI3 DNA   binding.   Expression of RY peaks during mid-maturation and drops during late   maturation, mimicking the MAT gene program, and in Arabidopsis thaliana   RY elements are over-represented in MAT, but not in LEA, genes. The   ABI3 transactivation of RY is inhibited by staurosporine, by a PP2C   phosphatase, and by a repressor of maturation genes, VAL1/HSI2.   The RY element mediates repression of MAT genes, and we propose that   transcriptional shutdown of the MAT program during late maturation   involves inhibition of ABI3 DNA binding by dephosphorylation. Later,   during seedling growth, VAL1/HSI2 family repressors silence MAT genes by binding RY elements.

Place, publisher, year, edition, pages
2009. Vol. 184, no 3, 552-565 p.
Keyword [en]
ABI3, embryo maturation, gene expression, repression, RY element, storage proteins
National Category
Biological Sciences
URN: urn:nbn:se:uu:diva-97159DOI: 10.1111/j.1469-8137.2009.02977.xISI: 000270902200006PubMedID: 19659659OAI: oai:DiVA.org:uu-97159DiVA: diva2:171977
Available from: 2008-04-28 Created: 2008-04-28 Last updated: 2010-07-01Bibliographically approved
In thesis
1. Studies on the regulation of the Napin napA promoter by ABI3, bZIP and bHLH transcription factors
Open this publication in new window or tab >>Studies on the regulation of the Napin napA promoter by ABI3, bZIP and bHLH transcription factors
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The B3-domain transcription factor ABI3 is a major regulator of gene expression of seed maturation during Arabidopsis embryogenesis. The napA gene encodes for a Brassica napus 2S storage protein specifically expressed in the embryo during the early and mid-maturation phase (MAT program).The napA promoter contains two essential cis-sequences; the B-box, which functions as an Abscisic acid-responsive element (ABRE) and the RY/G cluster. ABI3 is known to target both these cis-sequences. Several bZIP factors expressed during seed maturation, bZIP12, bZIP38 and bZIP66, as well as a heterodimer of ABI5 and bZIP67, can bind the B-box ABRE in a yeast one-hybrid assay. Amongst them ABI3 and bZIP67 are able to activate synergistically the two cis-elements in a transient protoplast assay. We also show that bZIP67 interacts directly with ABI3 in a yeast two-hybrid assay. Therefore, we hypothesize that i)ABI3 is recruited indirectly to napA through molecular interaction with bZIP67 bound to the B-box ABRE, ii) ABI3 binds directly to the RY-element and interacts with bZIP67 targeted to the adjacent G-box found in the napA RY/G-cluster.

We also show that the RY/G cluster is responsible for repression of napA expression during the late maturation LEA program, and for repression of ABI3-mediated transactivation during germination. ABI3 from which the A1 activation domain had been removed, can bind to the napA RY-element in a yeast one-hybrid assay, in contrast to full-length ABI3, suggesting that ABI3 DNA-binding abilities are regulated by auto-inhibition. We propose that during late maturation ABI3 loses ability to bind RY, which results in repression of MAT genes but not of LEA genes that contain fewer RY-elements. In parallel, we show that the B3-domain VAL proteins bind to RY-elements and decrease ABI3-mediated transactivation of the napA RY/G and therefore act as active repressors maintaining silencing of MAT genes during vegetative growth.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2008. 43 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 347
Molecular biology, transcription gene regulation, plant seed maturation, seed storage protein, ABA, ABI3, bZIP, bHLH, Brassica napus, Molekylärbiologi
urn:nbn:se:uu:diva-8713 (URN)978-91-554-7189-7 (ISBN)
Public defence
2008-05-20, C10:301, BMC, Uppsala, 09:15
Available from: 2008-04-28 Created: 2008-04-28Bibliographically approved

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