title: Functional and evolutionary analysis of DXL1, a non-essential gene encoding a 1-deoxy-D-xylulose 5-phosphate synthase like protein in Arabidopsis thaliana.
abstract: The synthesis of 1-deoxy-D-xylulose 5-phosphate (DXP), catalyzed by the enzyme DXP synthase (DXS), represents a key regulatory step of the 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway for isoprenoid biosynthesis. In plants DXS is encoded by small multigene families that can be classified into, at least, three specialized subfamilies. Arabidopsis thaliana contains three genes encoding proteins with similarity to DXS, including the well-known DXS1/CLA1 gene, which clusters within subfamily I. The remaining proteins, initially named DXS2 and DXS3, have not yet been characterized. Here we report the expression and functional analysis of A. thaliana DXS2. Unexpectedly, the expression of DXS2 failed to rescue Escherichia coli and A. thaliana mutants defective in DXS activity. Coherently, we found that DXS activity was negligible in vitro, being renamed as DXL1 following recent nomenclature recommendation. DXL1 is targeted to plastids as DXS1, but shows a distinct expression pattern. The phenotypic analysis of a DXL1 defective mutant revealed that the function of the encoded protein is not essential for growth and development. Evolutionary analyses indicated that DXL1 emerged from DXS1 through a recent duplication apparently specific of the Brassicaceae lineage. Divergent selective constraints would have affected a significant fraction of sites after diversification of the paralogues. Furthermore, amino acids subjected to divergent selection and likely critical for functional divergence through the acquisition of a novel, although not yet known, biochemical function, were identified. Our results provide with the first evidences of functional specialization at both the regulatory and biochemical level within the plant DXS family.
authors.affiliation: Departament de Bioquímica i Biologia Molecular, Facultat de Biologia, Universitat de Barcelona, Avda. Diagonal 643, 08028 Barcelona, Spain. lorenzoc@buffalo.edu
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Carretero-Paulet
authors.forename: Albert
authors.initials: A
authors.lastname: Cairó
authors.forename: David
authors.initials: D
authors.lastname: Talavera
authors.forename: Andreu
authors.initials: A
authors.lastname: Saura
authors.forename: Santiago
authors.initials: S
authors.lastname: Imperial
authors.forename: Manuel
authors.initials: M
authors.lastname: Rodríguez-Concepción
authors.forename: Narciso
authors.initials: N
authors.lastname: Campos
authors.forename: Albert
authors.initials: A
authors.lastname: Boronat
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D018076:DNA, Complementary / Q000235:genetics / Q000378:metabolism; D004789:Enzyme Activation; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D019143:Evolution, Molecular; D020440:Gene Duplication; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D005816:Genetic Complementation Test; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010428:Pentosephosphates / Q000378:metabolism; D010641:Phenotype; D010802:Phylogeny; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D018087:Plastids / Q000201:enzymology / Q000235:genetics; D014166:Transferases / Q000235:genetics* / Q000378:metabolism; D014170:Transformation, Genetic
chemical_list: C109460:1-deoxylulose 5-phosphate; D029681:Arabidopsis Proteins; D018076:DNA, Complementary; D010428:Pentosephosphates; D014166:Transferases; C109461:deoxyxylulose-5-phosphate synthase