Overexpression of a protein phosphatase 2C from beech seeds in Arabidopsis shows phenotypes related to abscisic acid responses and gibberellin biosynthesis.
A functional abscisic acid (ABA)-induced protein phosphatase type 2C (PP2C) was previously isolated from beech (Fagus sylvatica) seeds (FsPP2C2). Because transgenic work is not possible in beech, in this study we overexpressed this gene in Arabidopsis (Arabidopsis thaliana) to provide genetic evidence on FsPP2C2 function in seed dormancy and other plant responses. In contrast with other PP2Cs described so far, constitutive expression of FsPP2C2 in Arabidopsis, under the cauliflower mosaic virus 35S promoter, produced enhanced sensitivity to ABA and abiotic stress in seeds and vegetative tissues, dwarf phenotype, and delayed flowering, and all these effects were reversed by gibberellic acid application. The levels of active gibberellins (GAs) were reduced in 35S:FsPP2C2 plants, although transcript levels of AtGA20ox1 and AtGA3ox1 increased, probably as a result of negative feedback regulation, whereas the expression of GASA1 was induced by GAs. Additionally, FsPP2C2-overexpressing plants showed a strong induction of the Responsive to ABA 18 (RAB18) gene. Interestingly, FsPP2C2 contains two nuclear targeting sequences, and transient expression assays revealed that ABA directed this protein to the nucleus. Whereas other plant PP2Cs have been shown to act as negative regulators, our results support the hypothesis that FsPP2C2 is a positive regulator of ABA. Moreover, our results indicate the existence of potential cross-talk between ABA signaling and GA biosynthesis.
Reyes
David
D
Departamento de Fisiología Vegetal, Centro Hispano-Luso de Investigaciones Agrarias, Facultad de Biología, Universidad de Salamanca, 37007 Salamanca, Spain.
Rodríguez
Dolores
D
González-García
Mary Paz
MP
Lorenzo
Oscar
O
Nicolás
Gregorio
G
García-Martínez
José Luis
JL
Nicolás
Carlos
C
D000040:Abscisic Acid / Q000378:metabolism* / Q000494:pharmacology; D017360:Arabidopsis / Q000033:anatomy & histology / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D029964:Fagus / Q000196:embryology / Q000201:enzymology*; D005875:Gibberellins / Q000096:biosynthesis*; D049452:Green Fluorescent Proteins / Q000032:analysis; D008954:Models, Biological; D008969:Molecular Sequence Data; D009997:Osmotic Pressure; D010641:Phenotype; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D030821:Plants, Genetically Modified / Q000033:anatomy & histology / Q000187:drug effects / Q000201:enzymology; D000071636:Protein Phosphatase 2C; D011993:Recombinant Fusion Proteins / Q000032:analysis; D012639:Seeds / Q000235:genetics / Q000378:metabolism; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism
D029681:Arabidopsis Proteins; D005875:Gibberellins; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; C078703:rab18 protein, Arabidopsis; D049452:Green Fluorescent Proteins; D000040:Abscisic Acid; D010749:Phosphoprotein Phosphatases; D000071636:Protein Phosphatase 2C; D020691:rab GTP-Binding Proteins