Verweij Walter, Spelt Cornelis, Di Sansebastiano Gian-Pietro, Vermeer Joop, Reale Lara, Ferranti Francesco, Koes Ronald, Quattrocchio Francesca
Institute for Molecular Cell Biology, Graduate School of Experimental Plant Sciences, Vrije Universiteit, de Boelelaan 1087, 1081HV Amsterdam, The Netherlands.
Nat Cell Biol. 2008 Dec;10(12):1456-62. doi: 10.1038/ncb1805. Epub 2008 Nov 9.
The regulation of pH in cellular compartments is crucial for intracellular trafficking of vesicles and proteins and the transport of small molecules, including hormones. In endomembrane compartments, pH is regulated by vacuolar H(+)-ATPase (V-ATPase), which, in plants, act together with H(+)-pyrophosphatases (PPase), whereas distinct P-type H(+)-ATPases in the cell membrane control the pH in the cytoplasm and energize the plasma membrane. Flower colour mutants have proved useful in identifying genes controlling the pH of vacuoles where anthocyanin pigments accumulate. Here we show that PH5 of petunia encodes a P(3A)-ATPase proton pump that, unlike other P-type H(+)-ATPases, resides in the vacuolar membrane. Mutation of PH5 reduces vacuolar acidification in petals, resulting in a blue flower colour and abolishes the accumulation of proanthocyanidins (condensed tannins) in seeds. Expression of PH5 is directly activated by transcription regulators of the anthocyanin pathway, in conjunction with PH3 and PH4. Thus, flower coloration, a key-factor in plant reproduction, involves the coordinated activation of pigment synthesis and a specific pathway for vacuolar acidification.
细胞区室中pH值的调节对于囊泡和蛋白质的细胞内运输以及包括激素在内的小分子运输至关重要。在内膜区室中，pH值由液泡H(+)-ATP酶（V-ATP酶）调节，在植物中，V-ATP酶与H(+)-焦磷酸酶（PP酶）共同发挥作用，而细胞膜中不同的P型H(+)-ATP酶控制细胞质中的pH值并为质膜提供能量。花色突变体已被证明有助于鉴定控制花青素色素积累的液泡pH值的基因。在这里，我们表明矮牵牛的PH5编码一种P(3A)-ATP酶质子泵，与其他P型H(+)-ATP酶不同，它位于液泡膜中。PH5的突变会降低花瓣中的液泡酸化，导致花色变蓝，并消除种子中原花青素（缩合单宁）的积累。PH5的表达由花青素途径的转录调节因子与PH3和PH4共同直接激活。因此，花色作为植物繁殖中的一个关键因素，涉及色素合成和液泡酸化特定途径的协同激活。
