Disease relevance of GAI

• The GA derepressible repressor model predicts that high-level expression of GAI should confer dwarfism, and these observations are consistent with this prediction [1].
• Constructs permitting the expression of the GAI and gai open reading frames (ORFs) at higher (driven by the cauliflower mosaic virus 35S promoter) and lower (driven by the original Arabidopsis GAI promoter) levels in tobacco were made [2].

High impact information on GAI

• The mutated gene associated with the phenotype is a homologue of the wheat 'green revolution' gene Reduced height-1 (ref. 6) and the Arabidopsis gene GA insensitive (GAI) [3].
• Here we report the molecular cloning of GAI and a closely related gene GRS [4].
• GIS mediates the induction of GL1 expression by GA in inflorescence organs and is antagonized in its action by the DELLA repressor GAI [5].
• 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 [6].
• Overexpression of SLY1 in sly1-2 and sly1-10 plants rescues the recessive GA-insensitive phenotype of these mutants [7].

Biological context of GAI

• The Arabidopsis genome contains genes encoding five different DELLA proteins, the best known of which are GAI and RGA [8].
• RGA was found to be a member of the VHIID regulatory family, which includes the radial root organizing gene SCARECROW and another GA signal transduction repressor, GAI [9].
• RGA1 and RGA2 have been mapped, respectively, to chromosome II and I, and their expression in plant is constitutive [10].
• The GA-insensitive mutant gai showed reduced cell elongation but normal ploidy levels [11].
• In the GA-insensitive mutant gai and the mutant spy-3, in which the basal level of GA signaling is activated, CSI did not increase cell number, although both CSI and AVG stimulated cell elongation in these mutants [12].

Associations of GAI with chemical compounds

• Recessive, presumed loss-of-function alleles of GAI confer normal height and resistance to the GA biosynthesis inhibitor paclobutrazol [13].

Other interactions of GAI

• RGA (repressor of ga1-3) and GAI (gibberellin insensitive) are negative regulators of plant hormone gibberellin (GA) signaling in Arabidopsis [14].
• Here, we describe a screen for suppressors of the ABA-insensitive mutant ABI1-1 that enriches for GA auxotrophs and GA-insensitive mutants [15].
• RGA1, RGA2 and SCR share several structural features and may define a new family of genes [10].

References