Potential Sites of Bioactive Gibberellin Production during Reproductive Growth inArabidopsis 

Abstract

Gibberellin 3-oxidase (GA3ox) catalyzes the final step in the synthesis of bioactive gibberellins (GAs). We examined the expression patterns of all four GA3ox genes in Arabidopsis thaliana by promoter–β-glucuronidase gene fusions and by quantitative RT-PCR and defined their physiological roles by characterizing single, double, and triple mutants. In developing flowers, GA3ox genes are only expressed in stamen filaments, anthers, and flower receptacles. Mutant plants that lack both GA3ox1 and GA3ox3 functions displayed stamen and petal defects, indicating that these two genes are important for GA production in the flower. Our data suggest that de novo synthesis of active GAs is necessary for stamen development in early flowers and that bioactive GAs made in the stamens and/or flower receptacles are transported to petals to promote their growth. In developing siliques, GA3ox1 is mainly expressed in the replums, funiculi, and the silique receptacles, whereas the other GA3ox genes are only expressed in developing seeds. Active GAs appear to be transported from the seed endosperm to the surrounding maternal tissues where they promote growth. The immediate upregulation of GA3ox1 and GA3ox4 after anthesis suggests that pollination and/or fertilization is a prerequisite for de novo GA biosynthesis in fruit, which in turn promotes initial elongation of the silique.

The Gibberellin perception system evolved to regulate a pre-existing GAMYB-mediated system during land plant evolution

“…2c-e), where the sporopollenin material is produced for the outer wall development [9][10][11][21][22][23] . Considering that GAMYBs, CYP703As and GA biosynthesis genes in flowering plants are also co-expressed in the tapetal cells and microspores 1,8,12,[24][25][26] , these observations indicate that SmGAMYB activity in these tissues of Selaginella is required to mediate GA signalling during the outer wall formation of microspores.…”

Endogenous Diterpenes Derived from ent-Kaurene, a Common Gibberellin Precursor, Regulate Protonema Differentiation of the Moss Physcomitrella patens

“…S1). Previous studies have shown that the vegetative tissues of Arabidopsis and the fern S. moellendorffii contain approximately 1 ng g 21 dry weight (Hu et al, 2008) and 1 ng g 21 fresh weight GA 4 , respectively (Hirano et al, 2007). From LC-MS/MS measurement, GA 4 is presumably not present in P. patens, but if it is the amount must be less than 1.5 pg g 21 fresh weight (Supplemental Fig.…”

Gibberellic acid in plant

“…44 GA-deficient mutants in Arabidopsis and tomato showed abnormal stamen development, 45,46,47 while extreme GA deficiency revealed female sterility. 48,49 No viable pollen develops in severe GA-deficient mutants, and sepals, petals, and pistils are underdeveloped, leading in some cases even to premature abortion of the flower.…”