Further evidence for feedback regulation of gibberellin biosynthesis in pea

Abstract

In shoots of the garden pea (Pisum sati7um L.), the main (dwarf) mutants, compared with the WT. Metabolism experibioactive gibberellin (GA) is GA 1 , which is synthesised from ments did not provide convincing evidence for feedback regulation of 20-oxidation, possibly because GA 19 appears to be GA 20 by 3-hydroxylation. Gibberellin A 20 is produced from GA 19 , as part of the process known as GA 20-oxidation. metabolised rapidly, even in WT pea shoots. Both 3-hydroxylase and 20-oxidase transcript levels were markedly higher in Because these steps are thought to be negatively regulated by GA 1 , we compared the metabolism of labelled GA 19 and GA 20 the mutants than in isogenic WT lines. The results support previous suggestions that both biosynthetic steps are feedback-in mutants deficient in GA 1 , with that observed in isogenic wild-type (WT) plants. There was a large and specific increase regulated by GA 1 in pea. in the 3-hydroxylation of labelled GA 20 in the GA 1 -deficient

Control of Gibberellin Levels and Gene Expression during De-Etiolation in Pea

“…4). Feedback regulation of this gene is well established in pea (Martin et al, 1996;Ross et al, 1999). This appeared to be confirmed when the expression of PsGA20ox1 was examined in the sln and ls-1 mutants (Fig.…”

Changes in Gibberellin A1 Levels and Response during De-Etiolation of Pea Seedlings

“…1). A possible explanation is that the drop in GA 1 may act as a signal to up-regulate these transcript levels (perhaps via feedback regulation; Ait-Ali et al, 1999;Ross et al, 1999), which in turn acts to increase the endogenous level of GA 1 . The increase in GA 1 may also be attributed to a down-regulation of the 2␤-hydroxylation of GA 1 , although no subsequent decrease in the level of GA 8 was recorded to coincide with the subsequent increase in GA 1 .…”

Inhibition of growth of microcultured Hancornia speciosa shoots by 3β-hydroxylated gibberellins and one of their C-3 deoxy precursors

“…Viewed structurally, all of the GAs associated with a strong inhibition of elongation in H. speciosa are C 19 -GAs and, with the exception of GA 9 and GA 20 , all of these growth-inhibitory GAs (for in vitro-grown H. speciosa) are highly growth-active C-3β-hydroxylated GAs in other plants (Adams et al 1992). Since GA 20 is converted to GA 1 in higher plants by 3β-hydroxylation (Zeevaart et al 1993;Olsen et al 1995;Williams et al 1998;Ross et al 1999), it was not unexpected to find that GA 20 also inhibited elongation in microcultured shoots of H. speciosa to a degree similar to that seen for GA 1 (Fig. 2).…”