Expression patterns of the NPP1 protein phosphatase gene and biochemical activity of its encoded protein

Abstract

TheNPP1 cDNA encoding the catalytic subunit of a type 1 serine/threonine protein phosphatase (PP1) was previously cloned and characterized inNicotiana tabacum (Plant Mol Biol 36, 315？322,1998). In this study, the expression patterns ofNPP1 mRNA in response to various stimuli were examined to gain insight on the cellular function of the NPP1 protein.NPP1 mRNA accumulation was stimulated by Ca++, wounding, fungal elkitiors, and chitosan in leaves. However, with abscisic acid treatment, no change in transcript levels was observed. The recombinant NPP1 protein was catalytically active and could dephosphorylate the autophosphorylated recombinant NtCDPK1, a calcium-dependent protein kinase from tobacco.