Gibberellins Promote Trichome Formation by Up-RegulatingGLABROUS1in Arabidopsis1

Abstract

Trichome development is dependent on gibberellin (GA) signaling in Arabidopsis thaliana. Using the GA-deficient mutant ga1-3, the GA-response mutant spy-5, and uniconazol (a GA-biosynthesis inhibitor), we show that the GA level response correlates positively with both trichome number and trichome branch number. Two genes, GL1 and TTG, are required for trichome initiation. In ga1-3, coexpression of GL1 and R, the maize TTG functional homolog, under control of the constitutive 35S promoter, restored trichome development, whereas overexpression of neither GL1 nor R alone was sufficient to significantly suppress the glabrous phenotype. We next focused on GL1 regulation by GAs. In the double mutant the gl1-1 glabrous phenotype is epistatic to the spy-5 phenotype, suggesting that GL1 acts downstream of the GA signal transduction pathway. The activity of a ␤-glucuronidase reporter gene driven by the GL1 promoter was decreased in the wild type grown on uniconazol and showed a clear GA-dependent activation in ga1-3. Finally, quantification of GL1 transcript levels by reverse transcriptase-polymerase chain reaction demonstrated that relative to wild type, ga1-3 plants contained less transcript. These data support the hypothesis that GAs induce trichome development through up-regulation of GL1 and possibly TTG genes.

Disruption of the 1-deoxy-D-xylulose-5-phosphate reductoisomerase (DXR) gene results in albino, dwarf and defects in trichome initiation and stomata closure in Arabidopsis

“…When 10 µM GA 3 was applied, the transcript levels of GL1, TTG1, and SPY significantly increased or decreased, in a tendency opposite to that in dxr mutant (Figure 7). This result is consistent with the important role of GAs in trichome formation and development [43][44][45].…”

“…In addition to the albino phenotype, we also found trichome initiation and stomata closure defects as a result of DXR disruption. It was previously reported that GAs play important roles in trichome development by regulating trichome-associated genes including GL1, GL3, and SPY [41][42][43][44][45]. As GAs are a class of important products derived from MEP-related isoprenoid biosynthetic pathways, it is reasonable to link DXR disruption to the observed trichome developmental defects.…”

Jasmonic acid control of GLABRA3 links inducible defense and trichome patterning inArabidopsis

“…S4B in the supplementary material) (Larkin et al, 1994). Gibberellins are proposed to activate trichome formation by upregulating GL1 expression (Perazza et al, 1998). Our results, however, suggest that JA signaling activates the function of GL1 protein in an indirect manner.…”

AtGA3ox2, a Key Gene Responsible for Bioactive Gibberellin Biosynthesis, Is Regulated during Embryogenesis by LEAFY COTYLEDON2 and FUSCA3 in Arabidopsis

“…GA levels are in picograms per gram of fresh weight. by GAs (Perazza et al, 1998). Recently, it has been shown that FUS3 represses TTG1 expression in the epidermis of embryos (Tsuchiya et al, 2004).…”

“…While ABA biosynthesis is regulated both maternally and zygotically, the control of GA biosynthesis during seed development is largely unknown. Because seed development in Arabidopsis requires two processes-one that is regulated by LEC genes and a second that requires ABA (Raz et al, 2001)-and because trichome formation, a GAdependent process on leaves (Perazza et al, 1998), is observed on lec embryos, we investigated whether the GA pathway was misregulated in lec mutants.…”