GENES OF SER THR PROTEIN PHOSPHATASES OF PLANTS - DETECTION OF SEQUENCES RELATED TO PPT/RDGC/

An unknown sequence that may encode a fragment of the Ser/Thr protein phosphatase (designated PP6Zm) related to PPT/rdgC phosphatases was id entified using PCR on maize genomic DNA. A dbEST search using a partia l amino acid sequence of PP6Zm revealed a putative homolog of PP6Zm ex pressed in Arabidopsis thaliana (EMBL AT6726). A search of the SwissPr ot database indicated that the partial amino acid sequence of AT6726 h as the highest identity (54.3%) to the rdgC phosphatase from Drosophil a melanogaster. The maize phosphatase PP1Zm6, described previously as a PP1 isoform (EMBO J., 1993, vol. 12, p. 3497), was found by us to be a plant homolog of mammalian PPT. In addition, six fragments of new ( pseudo)genes homologous to the phosphatase genes encoding PP1, PP2A, a nd PPX isoforms were detected in the maize genome. The existence in ma ize of a multigene PP2A family, reported only for dicotyledons, and of a PP1 multigene family, found earlier in both di- and monocotyledons, was shown.