title: Protein phosphatase 2A holoenzyme and its subunits from Medicago sativa.
abstract: We detected an about 200 kDa holoenzyme of protein phosphatase 2A (PP2A) in the crude extract of Medicago sativa microcallus cells by gel permeation chromatography. By polymerase chain reaction (PCR) we isolated two M. sativa cDNA fragments corresponding to the catalytic (C) subunit, and one each coding for the A and the B regulatory subunits of PP2A. The C subunit sequences were different from that published previously, indicating the existence of at least three different isoforms in M. sativa. Using the PCR fragments as probes, we obtained two distinct full-length clones for both the A and B subunits from an alfalfa cDNA library. Our results demonstrate that the components of the PP2A holoenzyme, namely the catalytic and regulatory subunits, are present in alfalfa in several isoforms and that their sequences are highly similar to their plant, yeast and animal counterparts. The distinct regulatory subunit genes are constitutively expressed during the cell cycle. Interestingly, two A-B subunit pairs had parallel mRNA steady-state levels in different plant tissues suggesting that not all of the possible isoform combinations are present in all tissues. The expression of the MsPP2A Bbeta subunit form was induced by abscisic acid indicating a specific function for this protein in the stress response.
authors.affiliation: Institute of Plant Biology Biological Research Center of the Hungarian Academy of Sciences, Szeged.
authors.forename: E C
authors.initials: EC
authors.lastname: Tóth
authors.forename: E
authors.initials: E
authors.lastname: Vissi
authors.forename: I
authors.initials: I
authors.lastname: Kovács
authors.forename: A
authors.initials: A
authors.lastname: Szöke
authors.forename: J
authors.initials: J
authors.lastname: Ariño
authors.forename: P
authors.initials: P
authors.lastname: Gergely
authors.forename: D
authors.initials: D
authors.lastname: Dudits
authors.forename: V
authors.initials: V
authors.lastname: Dombrádi
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology; D000595:Amino Acid Sequence; D015152:Blotting, Northern; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D000455:Medicago sativa / Q000166:cytology / Q000201:enzymology / Q000235:genetics*; D008969:Molecular Sequence Data; D010749:Phosphoprotein Phosphatases / Q000235:genetics* / Q000378:metabolism; D010937:Plant Growth Regulators / Q000494:pharmacology; D054648:Protein Phosphatase 2; D021122:Protein Subunits; D018749:RNA, Plant / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution
chemical_list: D018076:DNA, Complementary; D007527:Isoenzymes; D010937:Plant Growth Regulators; D021122:Protein Subunits; D018749:RNA, Plant; D000040:Abscisic Acid; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2