Nuclear Localization of the Plant Protein Ser/Thr Phosphatase PP7

Abstract

Recently we identified novel plant Ser/Thr phosphatases, termed PP7, which belong to the PPP family and have no known close homologs in other kingdoms. We now addressed the intracellular location of Arabidopsis thaliana PP7 using GFP fusions and confocal laser scanning microscopy. PP7 · GFP fusion was expressed transiently or stably in Nicotiana benthamiana. PP7 · GFP was found to be a predominantly nuclear protein. Effects of cytoskeleton-disrupting drugs indicate that cytoskeleton may be required for efficient PP7 · GFP delivery to the nucleus. Deletion of a potential nuclear localization signal in the first insert in the catalytic domain, as well as exposure to the dark, cold, high salinity and abscisic acid failed to prevent nuclear localization of PP7 · GFP. Deletion of the 44 C-terminal amino acids resulted in a fusion protein located exclusively in the cytoplasm. The results suggest a possible similarity of the nuclear targeting signals in PP7 and the PP5/PPT subfamily.