Genetic Characterization and Functional Analysis of the GID1 Gibberellin Receptors inArabidopsis 

Abstract

We investigated the physiological function of three Arabidopsis thaliana homologs of the gibberellin (GA) receptor GIBBERELLIN-INSENSITIVE DWARF1 (GID1) by determining the developmental consequences of GID1 inactivation in insertion mutants. Although single mutants developed normally, gid1a gid1c and gid1a gid1b displayed reduced stem height and lower male fertility, respectively, indicating some functional specificity. The triple mutant displayed a dwarf phenotype more severe than that of the extreme GA-deficient mutant ga1-3. Flower formation occurred in long days but was delayed, with severe defects in floral organ development. The triple mutant did not respond to applied GA. All three GID1 homologs were expressed in most tissues throughout development but differed in expression level. GA treatment reduced transcript abundance for all three GID1 genes, suggesting feedback regulation. The DELLA protein REPRESSOR OF ga1-3 (RGA) accumulated in the triple mutant, whose phenotype could be partially rescued by loss of RGA function. Yeast two-hybrid and in vitro pull-down assays confirmed that GA enhances the interaction between GID1 and DELLA proteins. In addition, the N-terminal sequence containing the DELLA domain is necessary for GID1 binding. Furthermore, yeast three-hybrid assays showed that the GA-GID1 complex promotes the interaction between RGA and the F-box protein SLY1, a component of the SCF SLY1 E3 ubiquitin ligase that targets the DELLA protein for degradation.

NO FLOWERING IN SHORT DAY (NFL) is a bHLH transcription factor that promotes flowering specifically under short-day in Arabidopsis

“…GID1A, GIF1B and GID1C) at the apical tissue of nfl mutants compared with wt plants support this perturbation of the GA biosynthetic or catabolic pathway. Because the GA pathway has strong feedback regulation, as previously shown (Griffiths et al, 2006), these data strongly suggest that nfl is defective in the GA pathway. This behavior is similar to the svp mutant, although svp flowers late under both LD and SD conditions (Andres et al, 2014).…”

Gibberellin homeostasis and plant height control by EUI and a role for gibberellin in root gravity responses in rice

“…We propose that EUI influences the GA signaling network due to altered GA levels according to a feedback mechanism that is similar to that operating in GA biosynthesis. It is possible that the eui mutant plants accumulate high levels of bioactive GAs, and that the overproduction of bioactive GAs could feedback regulate GA signaling by decreasing the production of GID1 and GID2, since GA treatment reduced transcript abundance for all three GID1 genes of Arabidopsis [13]. Such high GA levels could also repress SLR1 expression as SLR1 protein accumulation was decreased or eliminated by GA treatment [5].…”

“…Many GA mutants show dramatically reduced plant height and hence increased yield potential and lodging resistance of modern cereal varieties, thus greatly contributing to the success of the 'green revolution' [8][9][10]. Recently, GID1 (GIBBERELLIN INSENSITIVE DWARF 1) was identified as a soluble GA receptor in rice and Arabidopsis [11][12][13].…”

Abscisic acid levels in tomato ovaries are regulated by LeNCED1 and SlCYP707A1

“…Abscisic acid was quantiWed in triplicates by GC-MS as described for GA analysis (GriYths et al 2006), but with modiWcations. Freeze-dried samples were homogenized in 50 mL 80% (v/v) methanol/water in 100 mL Xasks after which 300 ng 3-methyl-[ 2 H 3 ]ABA was added as internal standard.…”