Inger Holme

The endogenous phytase activity present in mature cereal grain is preformed during grain development and constitutes an important quality parameter for the utilization of phosphorus and minerals in food and feed. Cereals belonging to the Triticeae tribe are known to possess a significant preformed phytase activity in the mature grains, however varying significantly between the individual species. After multiple steps of chromatography, the phytase activity elutes as one peak, indicating that it consists of either one enzyme or more than one very similar enzymes. Recent work in our group** has demonstrated that these enzymes are purple acid phosphatase phytases (PAPhy’s) encoded by a few highly conserved mRNA’s expressed either during grain filling (PAPhy_a’s) or germination (PAPhy_b’s).
In the present study, 15 genomic PAPhy sequences from wheat, barley, rye, einkorn and Aegilops taushii were isolated and analyzed. Gene phylogeny and chromosomal mapping using aneuploid wheat and barley lines unravelled that the PAPhy_a and b’s constituted a set of paralogues located on the Triticeae chromosome 5 and 3, respectively. Cross-reference with sequenced and assembled grass genomes showed that this PAPhy duplication was shared only by the Triticeae sister tribe Brachypodium. In silico analysis of the Triticeae PAPhy promoters revealed a conserved 150 bp core promoter with two TATA-boxes. Upstream of this, the PAPhy_a and b promoters are without significant similarities. In this diverged section, PAPhy_b promoters contain elements typical of gibberellic acid induced germination related hydrolases. PAPhy_a promoters in contrast possess elements known from storage protein promoters.
**Dionisio G, Madsen CK, Holm PB, Welinder KG, Jørgensen M, Stoger E, Arcalis E, Brinch-Pedersen H. Cloning and Characterization of Purple Acid Phosphatase Phytases from Wheat (Triticum aestivum L.), Barley (Hordeum vulgare L.), Maize (Zea maize L.) and Rice (Oryza sativa L.). Plant Physiol. 2011a, Jan 10.[Epub ahead of print]