Aarhus University, Faculty of Science and Technology, Dept. of Molecular Biology and Genetics, Research Centre Flakkebjerg, DK-4200 Slagelse, Denmark.
J Exp Bot. 2013 Aug;64(11):3111-23. doi: 10.1093/jxb/ert116.
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.
植酸酶活性是食品和饲料的一个重要营养参数。在谷物灌浆过程中，小麦族成员积累紫色酸性磷酸酶植酸酶（PAPhy）。这种积累使成熟谷物植酸酶活性（MGPA）提高到大麦的 650 FTU/kg 左右，黑麦的 6000 FTU/kg 左右。这明显高于其他谷物。例如，水稻、玉米和燕麦的 MGPAs 低于 100 FTU/kg。本文报道了从小麦、大麦、黑麦、一粒小麦和节节麦中克隆和鉴定 PAPhy 基因的情况。小麦族 PAPhy 基因通常由一组同源基因 PAPhy_a 和 PAPhy_b 组成，分别定位在小麦族 5 号和 3 号染色体上。启动子具有保守核心，但 PAPhy_a 启动子获得了一个新的顺式作用调控元件，用于在灌浆期表达，而 PAPhy_b 启动子则保持了古老的功能，在萌发期驱动表达。拟南芥是唯一具有 PAPhy 重复序列的禾本科植物。与小麦族一样，这种重复反映在拟南芥 4200 FTU/kg 的高 MGPA 上。拟南芥 1 号和 2 号染色体上的同源基因座的序列保守性并未超出 PAPhy 基因。结果表明，单个基因片段的重复可能通过为亲本 PAPhy 基因创造功能冗余，从而促进了高 MGPA 的进化。这意味着在一些禾本科植物（如玉米和水稻）的育种计划中，可能无法达到类似的 MGPA 水平，而小麦族的育种者应重点关注 PAPhy_a。
