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- Olsson, Anna S. B., 1976-
(författare)
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HDZip I Transcription Factors in Arabidopsis thaliana : Expression and Function in Relation to Environmental Stress Conditions
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The homeodomain leucine zipper (HDZip) proteins constitute a plant-specific family of transcription factors, that based on sequence criteria have been grouped into four classes, HDZip I-IV. This thesis describes the phylogeny, function, expression patterns and regulation of the HDZip class I genes in the model species Arabidopsis thaliana. The phylogenetic analyses, traced duplication history and exon/intron organisation of the 17 class I genes in Arabidopsis show that the genes form six monophyletic groups, clades, with an origin in early plant evolution. All genes are expressed in broad tissue distribution patterns and the majority are responsive to water availability and/or light conditions. The expression of the genes show different patterns and dependence on environmental stress conditions, indicating evolutionary changes within and between clades. Ectopic expression of the genes suggest that they regulate genes in part by conserved mechanisms. Therefore, different functional roles seem to have evolved by a divergence mainly in the regulatory properties of the genes. Detailed expression analyses of the paralogous HDZip I genes ATHB7 and ATHB12 show that they have essentially overlapping patterns of activity in response to abscisic acid, ABA, or water deficit in leaves, stems and roots. The water deficit response of ATHB7 and -12 is mediated by ABA and depends on the protein phosphateses ABI1 and ABI2. Transgenic plants with ectopic expression of ATHB7 and/or -12, and athb7 and athb12 mutants, reveal that the genes in roots mediate the growth inhibitory effects of ABA. In this aspect of their function they do not overlap. In leaves and stems, the genes might act as growth regulators redundantly with other factors. Taken together these data suggest that ATHB7 and -12 regulate growth in response water deficit and that other HDZip I genes have related functions in response to environmental stress conditions.
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| 2. |
- Agalou, Adamantia, et al.
(författare)
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A genome-wide survey of HD-Zip genes in rice and analysis of drought-responsive family members
- 2008
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Ingår i: Plant Molecular Biology. - : Springer Science and Business Media LLC. - 0167-4412 .- 1573-5028. ; 66:1-2, s. 87-103
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Tidskriftsartikel (refereegranskat)abstract
- The homeodomain leucine zipper (HD-Zip) genes encode transcription factors that have diverse functions in plant development and have often been implicated in stress adaptation. The HD-Zip genes are the most abundant group of homeobox (HB) genes in plants and do not occur in other eukaryotes. This paper describes the complete annotation of the HD-Zip families I, II and III from rice and compares these gene families with Arabidopsis in a phylogeny reconstruction. Orthologous pairs of rice and Arabidopsis HD-Zip genes were predicted based on neighbour joining and maximum parsimony (MP) trees with support of conserved intron-exon organization. Additionally, a number of HD-Zip genes appeared to be unique to rice. Searching of EST and cDNA databases and expression analysis using RT-PCR showed that 30 out of 31 predicted rice HD-Zip genes are expressed. Most HD-Zip genes were broadly expressed in mature plants and seedlings, but others showed more organ specific patterns. Like in Arabidopsis and other dicots, a subset of the rice HD-Zip I and II genes was found to be regulated by drought stress. We identified both drought-induced and drought-repressed HD-Zip genes and demonstrate that these genes are differentially regulated in drought-sensitive versus drought-tolerant rice cultivars. The drought-repressed HD-Zip family I gene, Oshox4, was selected for promoter-GUS analysis, showing that drought-responsiveness of Oshox4 is controlled by the promoter and that Oshox4 expression is predominantly vascular-specific. Loss-of-function analysis of Oshox4 revealed no specific phenotype, but overexpression analysis suggested a role for Oshox4 in elongation and maturation processes.
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| 3. |
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| 4. |
- Kuijt, Suzanne J. H., et al.
(författare)
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Interaction between the GROWTH-REGULATING FACTOR and KNOTTED1-LIKE HOMEOBOX Families of Transcription Factors1[W]
- 2014
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Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 0032-0889 .- 1532-2548. ; 164:4, s. 1952-1966
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Tidskriftsartikel (refereegranskat)abstract
- KNOTTED1-LIKE HOMEOBOX (KNOX) genes are important regulators of meristem function, and a complex network of transcription factors ensures tight control of their expression. Here, we show that members of the GROWTH-REGULATING FACTOR (GRF) family act as players in this network. A yeast (Saccharomyces cerevisiae) one-hybrid screen with the upstream sequence of the KNOX gene Oskn2 from rice (Oryza sativa) resulted in isolation of OsGRF3 and OsGRF10. Specific binding to a region in the untranslated leader sequence of Oskn2 was confirmed by yeast and in vitro binding assays. ProOskn2: beta-glucuronidase reporter expression was down-regulated by OsGRF3 and OsGRF10 in vivo, suggesting that these proteins function as transcriptional repressors. Likewise, we found that the GRF protein BGRF1 from barley (Hordeum vulgare) could act as a repressor on an intron sequence in the KNOX gene Hooded/Barley Knotted3 (Bkn3) and that AtGRF4, AtGRF5, and AtGRF6 from Arabidopsis (Arabidopsis thaliana) could repress KNOTTED-LIKE FROM ARABIDOPSIS THALIANA2 (KNAT2) promoter activity. OsGRF overexpression phenotypes in rice were consistent with aberrant meristematic activity, showing reduced formation of tillers and internodes and extensive adventitious root/shoot formation on nodes. These effects were associated with down-regulation of endogenous Oskn2 expression by OsGRF3. Conversely, RNA interference silencing of OsGRF3, OsGRF4, and OsGRF5 resulted in dwarfism, delayed growth and inflorescence formation, and up-regulation of Oskn2. These data demonstrate conserved interactions between the GRF and KNOX families of transcription factors in both monocot and dicot plants.
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| 5. |
- Shao, Jingxia, et al.
(författare)
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Functional analysis of the HD-Zip transcription factor genes Oshox12 and Oshox14 in rice
- 2018
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Ingår i: PLOS ONE. - : PUBLIC LIBRARY SCIENCE. - 1932-6203. ; 13:7
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Tidskriftsartikel (refereegranskat)abstract
- The homeodomain-leucine zipper (HD-Zip) transcription factor family plays vital roles in plant development and morphogenesis as well as responses to biotic and abiotic stresses. In barley, a recessive mutation in Vrs1 (HvHox1) changes two-rowed barley to six-rowed barley, which improves yield considerably. The Vrs1 gene encodes an HD-Zip subfamily I transcription factor. Phylogenetic analysis has shown that the rice HD-Zip I genes Oshox12 and Oshox14 are the closest homologues of Vrs1. Here, we show that Oshox12 and Oshox14 are ubiquitously expressed with higher levels in developing panicles. Trans-activation assays in yeast and rice protoplasts demonstrated that Oshox12 and Oshox14 can bind to a specific DNA sequence, AH1 (CAAT(A/T)ATTG), and activate reporter gene expression. Overexpression of Oshox12 and Oshox14 in rice resulted in reduced panicle length and a dwarf phenotype. In addition, Oshox14 overexpression lines showed a deficiency in panicle exsertion. Our findings suggest that Oshox12 and Oshox14 may be involved in the regulation of panicle development. This study provides a significant advancement in understanding the functions of HD-Zip transcription factors in rice.
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