Inhibition of gibberellin biosynthesis by paclobutrazol in cell-free homogenates ofCucurbita maxima endosperm andMalus pumila embryos

Abstract

Abstract. The plant growth retardant paclobutrazol, (PP333) (2RS,3RS)-1 -(4-chlorophenyl) -4,4 -dimethyl -2 -(1,2,4-triazol-l-yl)pentan-3-ol, inhibits specifically the three steps in the oxidation of the gibberellin-precursor ent-kaurene to ent-kaurenoic acid in a cell-free system from Cttcurbita maxima endosperm. The KIs0 for this inhibition is 2 x 10 -8 M.The KIs0 values for the separated 2S,3S, and 2R,3R enantiomers of paclobutrazol in this system are 2 x 10 -8 M and 7 x 10 -7 M, respectively. A cell-free preparation from immature Mahts pumila embryos converts entkaurene to gibberellin A 9, whereas no conversion occurs in a similar preparation from Malus endosperm. The conversion of ent-kaurene by the embryo preparation is inhibited by paclobutrazol with KIs0 values for the 2S,3S and 2R

The Arabidopsis Mutant sleepy1gar2-1 Protein Promotes Plant Growth by Increasing the Affinity of the SCFSLY1 E3 Ubiquitin Ligase for DELLA Protein Substrates[W]

“…However, 35S:SLY1 conferred increased resistance to PAC, a GA biosynthesis inhibitor (Hedden and Graebe, 1985;Davis and Curry, 1991). 35S:SLY1 seeds germinated on PAC-containing medium (as did positive control gai sly1 gar2-1 seeds; Peng et al, 1999b), whereas the germination of wild-type control seeds was substantially inhibited ( Figure 4C).…”

Extragenic Suppressors of the Arabidopsis gaiMutation Alter the Dose-Response Relationship of Diverse Gibberellin Responses1

“…The Arabidopsis spy mutations confer resistance to the plant-growth and GA-biosynthesis inhibitor PAC (Hedden and Graebe, 1985;Davis and Curry, 1991) and suppress the effects of GA deficiency (Jacobsen and Olszewski, 1993;Jacobsen et al, 1996). Thus, although the GA-deficient ga1-2 mutant requires exogenous GA for germination (Koornneef and van der Veen, 1980;Sun et al, 1992), spy-1 ga1-2 double-mutant seeds germinate in the absence of exogenous GA (Jacobsen and Olszewski, 1993).…”

Expression cloning of a gibberellin 20-oxidase, a multifunctional enzyme involved in gibberellin biosynthesis.

“…Immature seeds of Cucurbita maxima are a rich source of GA-biosynthetic enzymes, and cell-free preparations from seed tissues ofthis species have proved of considerable value in elucidating GA-metabolic pathways (3,4) and in characterizing the enzymes involved (5). Recently, [gibberellin, 2-oxoglutarate:oxygen oxidoreductase (20-hydroxylating, oxidizing) EC 1.14.11.-] has been purified to apparent homogeneity from the endosperm/nucellus and shown to catalyze the conversion of GA12 to GA25 and of GA53 to GA17 and GA20 (see Fig.…”