Baldwin James C, Karthikeyan Athikkattuvalasu S, Cao Aiqin, Raghothama Kashchandra G
Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN 47907, USA.
Planta. 2008 Jul;228(2):273-80. doi: 10.1007/s00425-008-0736-y. Epub 2008 May 6.
Adaptation of plants to phosphate (Pi) deficiency is a complex process involving host of biochemical changes. These changes are integrated at transcriptional level by Pi starvation mediated signal transduction pathway. Many of the signaling processes are regulated by reversible protein phosphorylation directed by protein kinases and protein phosphatases. In this study, we report the characterization of a protein phosphatase gene (LePS2;1) from tomato induced during phosphate starvation. The bacterially expressed recombinant LePS2;1 protein readily dephosphorylated a synthetic phospho-Ser/Thr peptide. Okadaic acid, an inhibitor of Ser/Thr protein phosphatases, suppressed the enzyme activity. Western blot analysis revealed the Pi starvation dependent accumulation of LePS2;1 protein. Over-expression of LePS2;1 in tomato plants resulted in increased anthocyanin accumulation and acid phosphatase activity under Pi sufficient condition. Transgenic plants exhibited distinct changes in morphology and delayed flower initiation. These results provide evidence that the protein phosphatase LePS2;1, plays an important role in phosphate starvation induced processes in tomato. To our knowledge this is the first comprehensive analysis of a protein phosphatase induced during phosphate starvation.
植物对磷缺乏的适应是一个复杂的过程，涉及许多生化变化。这些变化通过磷饥饿介导的信号转导途径在转录水平上整合。许多信号传导过程由蛋白激酶和蛋白磷酸酶指导的可逆蛋白磷酸化调节。在本研究中，我们报道了番茄中一个在磷饥饿期间诱导表达的蛋白磷酸酶基因（LePS2;1）的特性。细菌表达的重组LePS2;1蛋白能轻易地使合成的磷酸化丝氨酸/苏氨酸肽去磷酸化。冈田酸，一种丝氨酸/苏氨酸蛋白磷酸酶抑制剂，抑制了该酶的活性。蛋白质印迹分析显示LePS2;1蛋白的积累依赖于磷饥饿。在磷充足的条件下，LePS2;1在番茄植株中的过表达导致花青素积累增加和酸性磷酸酶活性增强。转基因植株在形态上表现出明显变化，且开花起始延迟。这些结果证明蛋白磷酸酶LePS2;1在番茄磷饥饿诱导的过程中起重要作用。据我们所知，这是对磷饥饿期间诱导的蛋白磷酸酶的首次全面分析。
