title: Abscisic acid causes changes in gene expression involved in the induction of the landform of the liverwort Riccia fluitans L.
abstract: The conversion of the submerged form of Riccia fluitans to the landform either by transfer to a moist solid surface or by treatment with abscisic acid (ABA), is accompanied by the formation of a set of new polypeptides and concomitant down-regulation of other polypeptides. Changes in gene expression were analyzed by two-dimensional separations of proteins and differential screening of a cDNA library. One of the landform-specific proteins might depend on the expression of the newly discovered Ric 1 gene. The deduced amino acid sequence of the isolated Ric 1 cDNA clone codes for a protein with a molecular mass of 30.1 kDa. This polypeptide possesses two amino acid sequences which are repeated five times each and it is largely hydrophilic with the exception of a hydrophobic carboxyl-terminal region. Under ABA treatment the expression of the Ric 1 mRNA had already reached its maximum after 1 h of incubation. Transferring submerged thalli onto an agar surface resulted in a slower induction. The Ric 1 gene product shows homology to an embryo-specific polypeptide of carrot seeds and to the group 3 of late-embryogenesis-abundant (LEA) proteins. Interestingly, ABA treatment improved the desiccation tolerance of the submerged thalli. Additionally, ABA stimulated the synthesis of a protein which is immunologically related to a tonoplast protein. This finding, together with the fact that the ABA-induced landform exhibits an increased activity of several vacuolar enzymes, may indicate a special role of the tonoplast and the vacuole during ABA-induced conversion of the thallus from the submerged to the terrestrial form.
authors.affiliation: Julius-von-Sachs-Institut für Biowissenschaften, Universität Würzburg, Germany.
authors.forename: E M
authors.initials: EM
authors.lastname: Hellwege
authors.forename: K J
authors.initials: KJ
authors.lastname: Dietz
authors.forename: W
authors.initials: W
authors.lastname: Hartung
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism*; D000222:Adaptation, Physiological; D000595:Amino Acid Sequence; D001483:Base Sequence; D018076:DNA, Complementary / Q000302:isolation & purification; D018744:DNA, Plant / Q000235:genetics*; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics*; D015870:Gene Expression; D017343:Genes, Plant; D007700:Kinetics; D008969:Molecular Sequence Data; D020559:Monomeric GTP-Binding Proteins; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics*; D010944:Plants / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D014617:Vacuoles
chemical_list: D018076:DNA, Complementary; D018744:DNA, Plant; D010940:Plant Proteins; D000040:Abscisic Acid; D019204:GTP-Binding Proteins; C083726:ric1 protein, Oryza sativa; D020559:Monomeric GTP-Binding Proteins