title: High mature grain phytase activity in the Triticeae has evolved by duplication followed by neofunctionalization of the purple acid phosphatase phytase (PAPhy) gene.
abstract: The phytase activity in food and feedstuffs is an important nutritional parameter. Members of the Triticeae tribe accumulate purple acid phosphatase phytases (PAPhy) during grain filling. This accumulation elevates mature grain phytase activities (MGPA) up to levels between ~650 FTU/kg for barley and 6000 FTU/kg for rye. This is notably more than other cereals. For instance, rice, maize, and oat have MGPAs below 100 FTU/kg. The cloning and characterization of the PAPhy gene complement from wheat, barley, rye, einkorn, and Aegilops tauschii is reported here. The Triticeae PAPhy genes generally consist of a set of paralogues, PAPhy_a and PAPhy_b, and have been mapped to Triticeae chromosomes 5 and 3, respectively. The promoters share a conserved core but the PAPhy_a promoter have acquired a novel cis-acting regulatory element for expression during grain filling while the PAPhy_b promoter has maintained the archaic function and drives expression during germination. Brachypodium is the only sequenced Poaceae sharing the PAPhy duplication. As for the Triticeae, the duplication is reflected in a high MGPA of ~4200 FTU/kg in Brachypodium. The sequence conservation of the paralogous loci on Brachypodium chromosomes 1 and 2 does not extend beyond the PAPhy gene. The results indicate that a single-gene segmental duplication may have enabled the evolution of high MGPA by creating functional redundancy of the parent PAPhy gene. This implies that similar MGPA levels may be out of reach in breeding programs for some Poaceae, e.g. maize and rice, whereas Triticeae breeders should focus on PAPhy_a.
authors.affiliation: Aarhus University, Faculty of Science and Technology, Dept. of Molecular Biology and Genetics, Research Centre Flakkebjerg, DK-4200 Slagelse, Denmark.
authors.forename: Claus Krogh
authors.initials: CK
authors.lastname: Madsen
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Dionisio
authors.forename: Inger Bæksted
authors.initials: IB
authors.lastname: Holme
authors.forename: Preben Bach
authors.initials: PB
authors.lastname: Holm
authors.forename: Henrik
authors.initials: H
authors.lastname: Brinch-Pedersen
mesh_terms: D010832:6-Phytase / Q000378:metabolism*; D000135:Acid Phosphatase / Q000235:genetics / Q000378:metabolism*; D058431:Brachypodium / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D020440:Gene Duplication / Q000235:genetics; D006023:Glycoproteins / Q000235:genetics / Q000378:metabolism*; D001467:Hordeum / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D006109:Poaceae / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D014908:Triticum / Q000201:enzymology / Q000235:genetics / Q000378:metabolism
chemical_list: D006023:Glycoproteins; D010940:Plant Proteins; C091137:purple acid phosphatase; D000135:Acid Phosphatase; D010832:6-Phytase
keywords: Barley; Brachypodium; PAPhy; Triticeae; einkorn; gene duplication; phytase; purple acid phosphatase; wheat.
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