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GAR1, a DNA Binding Gibberellin Receptor, Directly Activates Gene Expression to Regulate Rice Height and Fertility

ABSTRACT: Gibberellins (GAs) regulate multiple aspects of growth and development in flowering plants, primarily through the canonical GID1-DELLA signaling module. Contrary to the prevailing paradigm that all GA responses require GID1, we demonstrated that a rice GID1-like 2 protein (designated GA Receptor 1, GAR1) is a GA receptor that functions independently of GID1. Isothermal titration calorimetry revealed that GAR1 can bind bioactive GAs, and multiple assays confirmed that GAR1 physically interacts with the promoter of GAMYB, a central regulator of GA responses, whereas GID1 does not. Using a transgenic rice line containing the GA biosensor GIBBERELLIN PERCEPTION SENSOR 1 (GPS1), we demonstrated that the subcellular distributions of GAR1 and its homologs GAR3 and GAR4 overlapped with strong GA signals in specific cells of rice leaves, anthers, and filaments. gar1 gar2 double mutants exhibited a semi-dwarf phenotype with slightly shorter anthers, whereas gar3 gar4 mutants displayed normal plant height with elongated filaments; both double mutants showed slightly reduced male fertility. ChIP-seq analyses revealed enrichment of GAR1 at the promoters of MYBs and other GA-responsive genes associated with tiller height and anther development, and RT-qPCR confirmed that height-related genes were downregulated in gar1 gar2 double mutants. Our findings reveal a non-canonical GA signaling pathway mediated by GAR1, providing new mechanistic insights into GA perception and novel targets for biotechnological manipulation.

ORGANISM(S): Oryza sativa

PROVIDER: GSE331473 | GEO | 2026/08/07

REPOSITORIES: GEO

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Project description:This model is from the article: Mathematical modeling elucidates the role of transcriptional feedback in gibberellin signaling. Middleton AM , Úbeda-Tomás S , Griffiths J , Holman T , Hedden P , Thomas SG , Phillips AL , Holdsworth MJ , Bennett MJ , King JR, Owen MR Proc. Natl. Acad. Sci. U.S.A. 2012 May; 109(19): 7571-6 22523240 , Abstract: The hormone gibberellin (GA) is a key regulator of plant growth. Many of the components of the gibberellin signal transduction [e.g., GIBBERELLIN INSENSITIVE DWARF 1 (GID1) and DELLA], biosynthesis [e.g., GA 20-oxidase (GA20ox) and GA3ox], and deactivation pathways have been identified. Gibberellin binds its receptor, GID1, to form a complex that mediates the degradation of DELLA proteins. In this way, gibberellin relieves DELLA-dependent growth repression. However, gibberellin regulates expression of GID1, GA20ox, and GA3ox, and there is also evidence that it regulates DELLA expression. In this paper, we use integrated mathematical modeling and experiments to understand how these feedback loops interact to control gibberellin signaling. Model simulations are in good agreement with in vitro data on the signal transduction and biosynthesis pathways and in vivo data on the expression levels of gibberellin-responsive genes. We find that GA-GID1 interactions are characterized by two timescales (because of a lid on GID1 that can open and close slowly relative to GA-GID1 binding and dissociation). Furthermore, the model accurately predicts the response to exogenous gibberellin after a number of chemical and genetic perturbations. Finally, we investigate the role of the various feedback loops in gibberellin signaling. We find that regulation of GA20ox transcription plays a significant role in both modulating the level of endogenous gibberellin and generating overshoots after the removal of exogenous gibberellin. Moreover, although the contribution of other individual feedback loops seems relatively small, GID1 and DELLA transcriptional regulation acts synergistically with GA20ox feedback.

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GAR1, a DNA Binding Gibberellin Receptor, Directly Activates Gene Expression to Regulate Rice Height and Fertility

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