Molecular characterization of plastidic phosphoserine aminotransferase in serine biosynthesis from Arabidopsis |
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Authors: | Chai-Ling Ho Masaaki Noji Maiko Saito Mami Yamazaki Kazuki Saito |
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Affiliation: | Laboratory of Molecular Biology and Biotechnology in Research Center of Medicinal Resources, Faculty of Pharmaceutical Sciences, Chiba University, Inage-ku, Yayoi-cho 1–33, Chiba 263–8522, Japan |
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Abstract: | Serine biosynthesis in plants proceeds by two pathways; a photorespiratory pathway which is associated with photorespiration and a pathway from phosphoglycerate. A cDNA encoding plastidic phosphoserine aminotransferase (PSAT) which catalyzes the formation of phosphoserine from phosphohydroxypyruvate has been isolated from Arabidopsis thaliana . Genomic DNA blot analysis indicated that this enzyme is most probably encoded by a single gene and is mapped on the lower arm of chromosome 4. The deduced protein contains an N-terminal extension exhibiting the general features of a plastidic transit peptide, which was confirmed by subcellular organelle localization using GFP (green flourescence protein). Northern analysis indicated preferential expression of PSAT in roots of light-grown plants, supporting the idea that the phosphorylated pathway may play an important role in supplying the serine requirement of plants in non-green tissues. In situ hybridization analysis of PSAT revealed that the gene is generally expressed in all types of cells with a significantly higher amount in the meristem tissue of root tips. |
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