Arabidopsis RGL1 encodes a negative regulator of gibberellin responses.
In Arabidopsis, the DELLA subfamily of GRAS regulatory genes consists of GAI, RGA, RGA-LIKE1 (RGL1), RGL2, and RGL3. GAI and RGA are known to be negative regulators of gibberellin (GA) responses. We found that RGL1 is a similar repressor of GA responses, as revealed by RGL1 gain-of-function and loss-of-function phenotypes. Repression of GA responses in Arabidopsis was conferred by a dominant 35S-rgl1 transgene carrying a DELLA domain deletion analogous to the GA-insensitive gai-1 mutation. As in GA-deficient Arabidopsis, the transgenic plants were dark green dwarfs with underdeveloped trichomes and flowers. Expression levels of GA4, a feedback-regulated GA biosynthetic gene, were increased correspondingly. Conversely, a loss-of-function rgl1 line had reduced GA4 expression and exhibited GA-independent activation of seed germination, leaf expansion, flowering, stem elongation, and floral development, as detected by resistance to the GA biosynthesis inhibitor paclobutrazol. RGL1 plays a greater role in seed germination than do GAI and RGA. The expression profile of RGL1 differed from those of the four other DELLA homologs. RGL1 message levels were predominant in flowers, with transcripts detected in developing ovules and anthers. As with RGA, green fluorescent protein (GFP)-tagged RGL1 protein was localized to the nucleus, but unlike GFP-RGA, there was no degradation after GA treatment. These findings indicate that RGL1 is a partially redundant, but distinct, negative regulator of GA responses and suggest that all DELLA subfamily members might possess separate as well as overlapping roles in GA signaling.
Wen
Chi-Kuang
CK
Department of Cell Biology and Molecular Genetics, Maryland Agricultural Experiment Station, H.J. Patterson Hall, University of Maryland, College Park, MD 20742, USA.
Chang
Caren
C
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics*; D002467:Cell Nucleus / Q000235:genetics; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000032:analysis; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D020868:Gene Silencing; D005875:Gibberellins / Q000494:pharmacology*; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D005810:Multigene Family; D009154:Mutation; D019913:Nuclear Localization Signals / Q000235:genetics; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics; D018514:Plant Structures / Q000187:drug effects / Q000235:genetics / Q000254:growth & development; D030821:Plants, Genetically Modified; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics; D014230:Triazoles / Q000494:pharmacology; D020726:ral Guanine Nucleotide Exchange Factor / Q000235:genetics
D029681:Arabidopsis Proteins; D018076:DNA, Complementary; C109555:GAI protein, Arabidopsis; D005875:Gibberellins; D008164:Luminescent Proteins; D019913:Nuclear Localization Signals; D010940:Plant Proteins; C450824:RGL1 protein, Arabidopsis; C450823:RGL2 protein, Arabidopsis; C485889:RGL3 protein, Arabidopsis; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D014230:Triazoles; D020726:ral Guanine Nucleotide Exchange Factor; D049452:Green Fluorescent Proteins; C053370:paclobutrazol