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Gene regulation by low level UV-B radiation: identification by DNA array analysis
Örebro University, Department of Natural Sciences. (Molekylär biokemi)
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2002 (English)In: Photochemical and Photobiological Sciences, ISSN 1474-905X, E-ISSN 1474-9092, Vol. 1, no 9, p. 656-664Article in journal (Refereed) Published
Abstract [en]

UV-B radiation alters transcript levels of various defence genes and photosynthetic genes in plants. Utilising a DNA array with 5000 ESTs and cDNAs from Arabidopsis thaliana, 70 genes were found to show a greater than two-fold induction or repression of transcript levels. Six genes (MEB5.2, PyroA, Ubq3, Lhcb6, F5D21.10 and the gene for an RNA polymerase II subunit) were tested for stress specific gene regulation on northern blots with RNA from plants exposed to low dose UV-B radiation, ozone or wounding. Transcript levels for PyroA, Uhq3 and the gene for a RNA polymerase II subunit were all specifically increased by UV-B. MEB5.2 mRNA levels also rose, whereas Lhcb6 and FSD21.10 transcript levels decreased under all stresses. The PyroA gene product in fungi is needed for biosynthesis of pyridoxine, and might have a role in protection against singlet oxygen. The Ubq3 gene encodes the ubiquitin protein that is attached to proteins destined for degradation. MEB5.2 and F5D21.10 represent novel gene products whose function have not yet been identified. Pairwise comparisons between the UV-B inducible promoters have identified a series of elements present in the MEB5.2 and PyroA promoters, absent from promoters of genes for early phenylpropanoid metabolism and that may be responsible for modulating their UV-B responses.

Place, publisher, year, edition, pages
2002. Vol. 1, no 9, p. 656-664
Keyword [en]
Arabidopsis/genetics/radiation effects, Base Sequence, DNA; Plant/genetics, Expressed Sequence Tags, Gene Expression Regulation; Enzymologic/radiation effects, Gene Expression Regulation; Plant/*radiation effects, Molecular Sequence Data, Oligonucleotide Array Sequence Analysis, Plant Proteins/genetics, Promoter Regions (Genetics), RNA Polymerase II/genetics, Ultraviolet Rays
National Category
Biochemistry and Molecular Biology
Research subject
Biochemistry
Identifiers
URN: urn:nbn:se:oru:diva-2879DOI: 10.1039/B202659GPubMedID: 12665302OAI: oai:DiVA.org:oru-2879DiVA, id: diva2:135398
Available from: 2005-09-14 Created: 2005-09-14 Last updated: 2017-12-14Bibliographically approved
In thesis
1. The molecular mechanisms behind perception and signal transduction of UV-B irradiation in Arabidopsis thaliana
Open this publication in new window or tab >>The molecular mechanisms behind perception and signal transduction of UV-B irradiation in Arabidopsis thaliana
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Elevation of UV-B radiation (280-315 nm), occurring as a result of depletion of the stratospheric ozone, causes a number of physiological and biochemical changes in plants. Damage to the photosynthetic apparatus (including the bleaching of the pigments which trap the sun's energy), to the processes of cell division and growth regulation, and to the composition and replication of genetic material are just some of these changes. The consequences include reduction in growth yield, changes in levels and effects of plant hormones and secondary metabolites, and alteration of interactions between plants and other organisms.

This thesis deals with several mechanistic questions related to regulation of responses during UV-B stress in plants. Our results show significant ecotype-specific variability in UV-B response in the model plant Arabidopsis thaliana. Differences at the molecular level (expression of PR-5 and steady-state concentration of H2O2) resulted in statistically significant differences in biomass, rosette size and leaf area. Therefore, it is of great importance to pay attention to the responses of the background ecotypes when for instance studying mechanisms of responses toward ultraviolet-B radiation in mutants.

Using a DNA microarray approach, we found a number of novel genes to be differentially expressed under UV-B radiation. Two of the genes (PYROA and MEB5.2) were later used as molecular markers for monitoring of UV-B stress. Promoters of PYROA and MEB5.2 were compared with promoters of genes for the phenylpropanoid pathway. The comparisons indicated only few common elements with the UV-B-regulated promoters of CHS, PAL and CHI. In contrast, the genes identified as being UV-B regulated in this study (MEB5.2, PYROA and UBQ3), completely lacked elements required for the UV-B induction of CHS, indicating that these genes are regulated by different transcription factors. In addition, novel unidentified cis-elements are probably also present upstream of the transcription start.

Reverse and forward genetics were used for searching novel genes responsive to UV-B and for examination of proposed candidates of the UV-B signal transduction chain. Screening of more than 2000 T-DNA mutants for differential response to UV-B resulted in the identification of a mutant displaying insensitivity to UV-B induced inhibition of hypocotyl growth. By using the corresponding knock-out mutants, the involvement of NADPH oxidase and MAPK phosphatase 1 in UV-B signalling was demonstrated.

For the plant to be able to respond appropriately to UV-B irradiation, UV-B quanta have to be absorbed. There are indirect evidences for the existence of specific UV-B receptor(s), whereas the receptor itself still remains unknown. By the classical approach of action spectroscopy, we undertook an attempt to identify the absorption spectra of the chromophore(s) sensing UV-B radiation in plants. The investigated molecular markers revealed the presence of two potential chromophores absorbing in the UV-B region and peaking at 280-290 and 300 nm, respectively.

Place, publisher, year, edition, pages
Örebro: Örebro universitetsbibliotek, 2005. p. 52
Series
Örebro Studies in Life Science ; 1
Keyword
Action spectroscopy, Arabidopsis, gene expression, reverse genetics, signal transduction, UV-B irradiation.
National Category
Medical Biotechnology (with a focus on Cell Biology (including Stem Cell Biology), Molecular Biology, Microbiology, Biochemistry or Biopharmacy)
Research subject
Biochemistry
Identifiers
urn:nbn:se:oru:diva-174 (URN)91-7668-450-4 (ISBN)
Public defence
2005-10-05, Hörsal F1, Forumhuset, Fakultetsgatan 1, Örebro, 10:00 (English)
Opponent
Supervisors
Available from: 2005-09-14 Created: 2005-09-13 Last updated: 2017-10-18Bibliographically approved

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Kalbina, IrinaStrid, Åke

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