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- Karpinska, B., et al.
(författare)
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MYB transcription factors are differentially expressed and regulated during secondary vascular tissue development in hybrid aspen
- 2004
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Ingår i: Plant Molecular Biology. - : Springer Science and Business Media LLC. - 0167-4412 .- 1573-5028. ; 56:2, s. 255-270
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Tidskriftsartikel (refereegranskat)abstract
- More than 120,000 poplar ESTs have been sequenced from 20 different cDNA libraries by the Swedish Centre for Tree Functional Genomics. We screened this EST collection for MYB transcription factors involved in secondary vascular tissue formation, and genes assigned as PttMYB3Ra, PttMYB4a and PttMYB21a were selected for further characterisation. Three MYB genes showed different expression patterns in various organs, tissues and stem sub-sections representing different developmental stages of vascular tissue formation. Furthermore, the analysis showed that PttMYB21a expression was much higher in secondary cell wall formation zone of xylem and phloem fibers than in other developmental zones. Transgenic hybrid aspen plants, expressing the 3'-part of the PttMYB21a gene in antisense orientation were generated to assess the function of PttMYB21a gene in vascular tissue formation and lignification. All transgenic lines showed reduced growth and had fewer internodes compared to the wild-type. The analysis of selected lines showed that acid soluble lignin present in the bark was higher in transgenic lines as compared to wild-type plants. Moreover a higher transcript level of caffeoyl-CoA 3-O-methyltransferase [CCoAOMT];EC2.1.1.104) was found in the phloem of the transgenic plants, suggesting that PttMYB21a might function as a transcriptional repressor.
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- Srivastava, A, et al.
(författare)
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Localization of phosphatidylserine binding sites to structural domains of factor X-a
- 2002
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 277:3, s. 1855-1863
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Tidskriftsartikel (refereegranskat)abstract
- Binding of short chain phosphatidylserine (C6PS) enhances the proteolytic activity of factor X-a by 60-fold (Koppaka, V., Wang, J., Banerjee, M., and Lentz, B. R. (1996) Biochemistry 35, 7482-7491). In the present study, we locate three C6PS binding sites to different domains of factor X-a using a combination of activity, circular dichroism, fluorescence, and equilibrium dialysis measurements on proteolytic and biosynthetic fragments of factor X-a. Our results demonstrate that the structural responses of human and bovine factor X. to C6PS binding are somewhat different. Despite this difference, data obtained with fragments from both human and bovine factor X-a are consistent with a common hypothesis for the location of C6PS binding sites to different structural domains. First, the gamma-carboxyglutamic acid (Gla) domain binds C6PS only in the absence of Ca2+ (k(d) similar to 1 mm), although this PS site does not influence the functional response of factor X-a. Second, a Ca2+-dependent binding site is in the epidermal growth factor domains (EGF(NC)) that are linked by Ca2+ and C6PS binding to the Gla domain. This site appears to be the lipid regulatory site of factor X-a. Third, a Ca2+-requiring site seems to be in the EGF(C)-catalytic domain. This site appears not to be a lipid regulatory site but rather to share residues with the substrate recognition site. Finally, the full functional response to C6PS requires linkage of the Gla, EGF(NC), and catalytic domains in the presence of Ca2+, meaning that PS regulation of factor X-a involves linkage between widely separated parts of the protein.
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