In C 4 plants, phosphoenolpyruvate carboxylase (PEPC; EC 4.1.1.31), a key enzyme in C 4 photosynthesis, is controlled by reversible phosphorylation of a conserved Ser residue near the N-terminus. We now report the first cloning of a cDNA from a C 4 plant, Flaveria trinervia, which encodes the specific protein kinase (FtPEPC-PK) involved in the phosphorylation of C 4 -form PEPC. Several lines of supportive evidence are: strict substrate specificity of the recombinant enzyme, prominent light/dark response of the transcript level and abundant expression in leaves of C 4 plant (F. trinervia) but very low expression in a C 3 plant of the same genus (Flaveria pringlei). We also discuss the possibility that the FtPEPC-PK gene has co-evolved with the PEPC gene to participate in C 4 photosynthesis. ß 2001 Published by Elsevier Science B.V. on behalf of the Federation of European Biochemical Societies.
TAF10 is one of the TATA box-binding protein-associated factors (TAFs), which constitute the TFIID complex. We isolated a plant TAF10 ortholog from a Flaveria trinervia cDNA library, and named it ftTAF10. The ftTAF10 polypeptide contains a histone-fold motif, which is highly conserved among the TAF10s of other organisms. A transiently expressed green fluorescent protein (GFP) fusion protein was translocated into the nuclei of onion epidermal cells, suggesting that the ftTAF10 functions in nuclei. The transcript level was higher in stems and roots than in leaves, and in situ hybridization of F. trinervia seedlings revealed that the ftTAF10 transcript is accumulated abundantly in vascular tissues of hypocotyls, in the central cylinder of roots, and slightly in bundle sheath cells of leaves. Overexpression of ftTAF10 in Arabidopsis under the cauliflower mosaic virus 35S promoter caused two kinds of abnormal morphology, limitation of the indeterminate inflorescence and production of deformed leaves. These results indicate the possibility that ftTAF10 is a plant 'selective TAF' involved in the expression of a subset of vascular abundant genes, and that its appropriate gene expression is necessary for normal development.
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