title: The plant-specific SR45 protein negatively regulates glucose and ABA signaling during early seedling development in Arabidopsis.
abstract: The plant-specific SR45 belongs to the highly conserved family of serine/arginine-rich (SR) proteins, which play key roles in precursor-mRNA splicing and other aspects of RNA metabolism. An Arabidopsis (Arabidopsis thaliana) loss-of-function mutant, sr45-1, displays pleiotropic phenotypes, such as defects in flower and leaf morphology, root growth, and flowering time. Here, we show that the sr45-1 mutation confers hypersensitivity to glucose (Glc) during early seedling growth in Arabidopsis. Unlike wild-type plants, the sr45-1 mutant displays impaired cotyledon greening and expansion as well as reduced hypocotyl elongation of dark-grown seedlings when grown in the presence of low (3%) Glc concentrations. In addition, SR45 is involved in the control of Glc-responsive gene expression, as the mutant displays enhanced repression of photosynthetic and nitrogen metabolism genes and overinduction of starch and anthocyanin biosynthesis genes. Like many other sugar response mutants, sr45-1 also shows hypersensitivity to abscisic acid (ABA) but appears to be unaffected in ethylene signaling. Importantly, the sr45-1 mutant shows enhanced ability to accumulate ABA in response to Glc, and the ABA biosynthesis inhibitor fluridone partially rescues the sugar-mediated growth arrest. Moreover, three ABA biosynthesis genes and two key ABA signaling genes, ABI3 and ABI5, are markedly overinduced by Glc in sr45-1. These results provide evidence that the SR45 protein defines a novel player in plant sugar response that negatively regulates Glc signaling during early seedling development by down-regulating both Glc-specific ABA accumulation and ABA biosynthesis and signaling gene expression.
authors.affiliation: Instituto Gulbenkian de Ciência, Oeiras, Portugal.
authors.forename: Raquel Fonseca
authors.initials: RF
authors.lastname: Carvalho
authors.forename: Sofia Domingues
authors.initials: SD
authors.lastname: Carvalho
authors.forename: Paula
authors.initials: P
authors.lastname: Duque
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D005030:Ethylenes / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D005816:Genetic Complementation Test; D005947:Glucose / Q000378:metabolism*; D016254:Mutagenesis, Insertional; D009154:Mutation; D010937:Plant Growth Regulators / Q000378:metabolism; D016601:RNA-Binding Proteins; D036226:Seedlings / Q000254:growth & development* / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D005030:Ethylenes; D010937:Plant Growth Regulators; D016601:RNA-Binding Proteins; C483303:SR45 protein, Arabidopsis; D000040:Abscisic Acid; C036216:ethylene; D005947:Glucose