Gibberellin A₁ Biosynthesis in Pisum sativum L.

Abstract

A comparative study of the metabolism of radiolabeled gibberellin (GA) 1, 19, and 20 in isolated vegetative tissues of isogenic Le and le pea (Pisum sativum) plants incubated in vitro with the appropriate GA substrate is described. The results of this study provide evidence that the enzymes involved in the latter stages of GA biosynthesis are spatially separated within the growing pea plant. Apical buds were not apparently involved in the production of bioactive GA1 or its immediate precursors. The primary site of synthesis of GA2o from GA1, was immature leaflets and tendrils, and the synthesis of bioactive GA, and its inactive catabolite GAs occurred predominantly in stem tissue. GA29, the inactive catabolite of GA20, was produced to varying extents in all the tissues examined. Little or no difference was observed in the ability of corresponding Le and le tissues to metabolize radiolabeled GA,, GA19, or

Auxin Regulation of the Gibberellin Pathway in Pea

“…This is the first time, to our knowledge, that isolated stem tissue of pea, or any isolated section of pea, has been unequivocally shown to exhibit PsGA3ox1 activity. Past studies have attempted to culture excised pea stem segments to investigate the effect of the le mutation on the metabolism of applied radiolabeled GA 20 (Smith, 1992;Sherriff et al, 1994). In light of current results, the lack of GA 1 peaks observed by Sherriff et al (1994) was attributable to the absence of auxin in the incubation medium, which resulted in the majority of applied GA 20 being converted to GA 29 (Fig.…”

“…Earlier, Smith (1992) proposed that GA 1 was a product of GA 20 in Murashige and Skoogcultured stem tissue, but Sherriff et al (1994) suggested that the product concerned was in fact GA 29 -catabolite. The subsequent work of Ross et al (2000) suggests that the lack of GA 1 -like peaks (and therefore a lack of GA 8 -like peaks) reported by Sheriff et al might be attributable to the absence of IAA in the culture medium.…”

“…Incubation times ranged from 4 to 24 h, as detailed for each experiment. This technique was based on the work of Smith (1992). After the incubation period, material for GA or IAA analyses was rinsed twice in distilled water to remove residual substrate, then immersed in cold (Ϫ20°C) 80% (v/v) methanol, and stored in a freezer at Ϫ20°C.…”

Mendel’s Genes: Toward a Full Molecular Characterization

“…These included a role not only in controlling gibberellin levels but also in determining the sensitivity (Kende and Lang 1964) or turnover (Kohler 1970) of gibberellins, or the level of various growth inhibitors (Kohler and Lang 1963;Chailakhyan 1979;Smith 1992). However, during the 1980s it became increasingly clear that LE was involved with regulating the level of the bioactive gibberellin GA 1 by influencing gibberellin biosynthesis.…”

Distribution of Gibberellins in Lathyrus odoratus L. and Their Role in Leaf Growth

“…Finally, environmental or developmental factors that alter the level of GAI and leaf growth in sweet pea have not been identified. The possible involvement of GAI in the growth of sweet pea leaves has assumed added significance in view of uncertainty regarding such a role in the garden pea (Smith, 1992). Although in garden pea it is now clear that gene le (which, like gene 1, also partially blocks the 3P-hydroxylation of GA2,; Ingram et al, 1984) reduces the level of GA, in leaves, coincident changes in leaf development have not been defined .…”