title: Della proteins and gibberellin-regulated seed germination and floral development in Arabidopsis.
abstract: RGA (repressor of ga1-3) and GAI (gibberellin insensitive) are negative regulators of plant hormone gibberellin (GA) signaling in Arabidopsis. The GA-deficient mutant ga1-3 is a nongerminating, extreme dwarf that flowers late and produces male-sterile flowers. The rga and gai null alleles interact synergistically to rescue vegetative growth and floral initiation in ga1-3, indicating that RGA and GAI are major repressors for these processes. However, rga and gai in combination cannot rescue seed germination or floral development in ga1-3. RGA and GAI belong to the DELLA subfamily within the GRAS family of plant regulatory proteins. Three additional DELLA proteins RGL1, RGL2, and RGL3 are present in Arabidopsis. Previous studies provided evidence that RGL2 and possibly RGL1 control seed germination. To investigate further the function of the RGL genes, we examined the expression profiles of all 5 DELLA protein genes by real-time PCR. RGA and, to a lesser extent, GAI mRNAs were expressed ubiquitously in all tissues, whereas RGL1, 2, and 3 transcripts were present at high levels only in germinating seeds and/or flowers and siliques. Using the newly isolated rgl1, rgl2, and rgl3 T-DNA insertion mutants, we demonstrated that RGL2 is the major repressor in seed germination. We further provided evidence that RGA, RGL1, and RGL2 are all involved in modulating floral development. Interestingly, RGL2 expression is regulated not only at the transcript level. We showed that RGL2 protein in imbibed seeds is rapidly degraded by GA treatment and that the F-box protein SLY1 is required for RGL2 degradation to occur.
authors.affiliation: Department of Biology, Duke University, Durham, North Carolina 27708, USA.
authors.forename: Ludmila
authors.initials: L
authors.lastname: Tyler
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Thomas
authors.forename: Jianhong
authors.initials: J
authors.lastname: Hu
authors.forename: Alyssa
authors.initials: A
authors.lastname: Dill
authors.forename: Jose M
authors.initials: JM
authors.lastname: Alonso
authors.forename: Joseph R
authors.initials: JR
authors.lastname: Ecker
authors.forename: Tai-Ping
authors.initials: TP
authors.lastname: Sun
mesh_terms: D019883:Alkyl and Aryl Transferases; D000483:Alleles; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000254:growth & development*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D005298:Fertility / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D035264:Flowers / Q000187:drug effects / Q000235:genetics / Q000254:growth & development*; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D018525:Germination / Q000187:drug effects / Q000502:physiology*; D005875:Gibberellins / Q000378:metabolism* / Q000494:pharmacology; D009154:Mutation; D010937:Plant Growth Regulators / Q000378:metabolism / Q000494:pharmacology; D010940:Plant Proteins; D012639:Seeds / Q000187:drug effects / Q000235:genetics / Q000254:growth & development*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D020798:Two-Hybrid System Techniques; D020726:ral Guanine Nucleotide Exchange Factor / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D004269:DNA, Bacterial; D005875:Gibberellins; D010937:Plant Growth Regulators; D010940:Plant Proteins; C450824:RGL1 protein, Arabidopsis; C450823:RGL2 protein, Arabidopsis; C485889:RGL3 protein, Arabidopsis; C036483:T-DNA; D014157:Transcription Factors; D020726:ral Guanine Nucleotide Exchange Factor; D019883:Alkyl and Aryl Transferases; C476121:SLY1 protein, Arabidopsis