title: The phytochelatin synthase gene in date palm (Phoenix dactylifera L.): Phylogeny, evolution and expression.
abstract: We studied date palm phytochelatin synthase type I (PdPCS1), which catalyzes the cytosolic synthesis of phytochelatins (PCs), a heavy metal binding protein, in plant cells. The gene encoding PdPCS1 (Pdpcs) consists of 8 exons and 7 introns and encodes a protein of 528 amino acids. PCs gene history was studied using Notung phylogeny. During evolution, gene loss from several lineages was predicted including Proteobacteria, Bilateria and Brassicaceae. In addition, eleven gene duplication events appeared toward interior nodes of the reconciled tree and four gene duplication events appeared toward the external nodes. These latter sequences belong to species with a second copy of PCs suggesting that this gene evolved through subfunctionalization. Pdpcs1 gene expression was measured in seedling hypocotyls exposed to Cd, Cu and Cr using quantitative real-time polymerase chain reaction (qPCR). A Pdpcs1 overexpression was evidenced in P. dactylifera seedlings exposed to metals suggesting that 1-the Pdpcs1 gene is functional, 2-there is an implication of the enzyme in metal detoxification mechanisms. Additionally, the structure of PdPCS1 was predicted using its homologue from Nostoc (cyanobacterium, NsPCS) as a template in Discovery studio and PyMol software. These analyses allowed us to identify the phytochelatin synthase type I enzyme in date palm (PdPCS1) via recognition of key consensus amino acids involved in the catalytic mechanism, and to propose a hypothetical binding and catalytic site for an additional substrate binding cavity.
authors.affiliation: Laboratory of Plant Biotechnology, Faculty of Sciences, University of Sfax, BP 1171, 3000 Sfax, Tunisia; Laboratoire de Génie Civil et géo-Environnement, Université de Lille 1, F-59655 Villeneuve d'Ascq, France.
authors.forename: Chaâbene
authors.initials: C
authors.lastname: Zayneb
authors.affiliation: Laboratory of Plant Biotechnology, Faculty of Sciences, University of Sfax, BP 1171, 3000 Sfax, Tunisia.
authors.forename: Rekik Hakim
authors.initials: RH
authors.lastname: Imen
authors.affiliation: Laboratory of Plant Biotechnology, Faculty of Sciences, University of Sfax, BP 1171, 3000 Sfax, Tunisia.
authors.forename: Kriaa
authors.initials: K
authors.lastname: Walid
authors.affiliation: Biorecycling Operations Research Laboratory, Des Moines, IA, USA.
authors.forename: C Douglas
authors.initials: CD
authors.lastname: Grubb
authors.affiliation: Laboratory of Plant Biotechnology, Faculty of Sciences, University of Sfax, BP 1171, 3000 Sfax, Tunisia.
authors.forename: Khemakhem
authors.initials: K
authors.lastname: Bassem
authors.affiliation: Laboratoire de Génie Civil et géo-Environnement, Université de Lille 1, F-59655 Villeneuve d'Ascq, France.
authors.forename: Vandenbulcke
authors.initials: V
authors.lastname: Franck
authors.affiliation: Laboratory of Plant Biotechnology, Faculty of Sciences, University of Sfax, BP 1171, 3000 Sfax, Tunisia.
authors.forename: Mejdoub
authors.initials: M
authors.lastname: Hafedh
authors.affiliation: Laboratory of Plant Biotechnology, Faculty of Sciences, University of Sfax, BP 1171, 3000 Sfax, Tunisia. Electronic address: amineelleuch@hotmail.com.
authors.forename: Elleuch
authors.initials: E
authors.lastname: Amine
mesh_terms: D000595:Amino Acid Sequence; D019881:Aminoacyltransferases / Q000235:genetics* / Q000378:metabolism; D020029:Base Pairing; D001483:Base Sequence; D030541:Databases, Genetic; D019143:Evolution, Molecular; D018506:Gene Expression Regulation, Plant; D005978:Glutathione / Q000378:metabolism; D018546:Hypocotyl / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D019216:Metals, Heavy / Q000633:toxicity*; D008958:Models, Molecular; D065749:Phoeniceae / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D010802:Phylogeny; D054811:Phytochelatins / Q000096:biosynthesis / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D012989:Soil Pollutants / Q000633:toxicity*
chemical_list: D019216:Metals, Heavy; D010940:Plant Proteins; D012989:Soil Pollutants; D054811:Phytochelatins; D019881:Aminoacyltransferases; C093784:glutathione gamma-glutamylcysteinyltransferase; D005978:Glutathione
keywords: Ancestral sequence; Duplication events; Gene loss; Pdpcs1 gene expression; Phylogenetic tree; Substrate binding site