Protein tyrosine phosphatases in higher plants

Reversible protein phosphorylation is the most common mechanism for cellula r regulation in eukaryotic systems. Indeed, approximately 5% of the Arabido psis genome encodes protein kinases and phosphatases. Among the thousands o f such enzymes, only a small fraction has been examined experimentally. Stu dies have demonstrated that Ser/Thr phosphorylation and dephosphorylation p lay a key role in the regulation of plant physiology acid development. Howe ver, function of tyrosine phosphorylation, despite the overwhelming importa nce in animals, has not been systematically studied in higher plants. As a result, it is still controversial whether tyrosine phosphorylation is impor tant in plant signal transduction. Recently, the first two protein tyrosine phosphatases (PTPs) from a higher plant were characterized. A diverse grou p of genes encoding putative PTPs have been identified from the Arabidopsis genome sequence databases. Genetic analyses of various PTPs are underway a nd preliminary results have provided evidence that these PTPs serve critica l functions in plant responses to stress signals and in plant development. (C) New Phytologist (2001) 151. 155-164.