Expression of gibberellin mutations in fruits of Pisum sativum L.

Abstract

The gibberellin (GA) economy of young pea (Pisum sativum L.) fruits was investigated using a range of mutants with altered GA biosynthesis or deactivation. The synthesis mutation lh-2 substantially reduced the content of both GA 4 and GA 1 in young seeds. Among the other synthesis mutations, ls-1, le-1 and le-3, the largest reduction in seed GA 1 content was only 1.7-fold (le-1), while GA 4 was not reduced in these mutants, and in fact accumulated in some experiments (compared with the wild type). Mutation sln appeared to block the step GA 20 to GA 29 in young pods and seeds, but not as strongly as in older seeds. Mutations ls-1, le-1 and le-3 markedly reduced pod GA 1 levels, but pod elongation was not aected. After feeds of [ 13 C, 3 H]GA 20 to leaves, the pods contained 13 C, 3 H-labelled GA 20 , GA 1 , GA 29 and GA 81 , and the seeds, [ 13 C, 3 H]GA 20 and [ 13 C, 3 H]GA 29 . These ®ndings are discussed in relation to recent suggestions regarding the role and origin of GA 1 in pea fruits.

Pollination-, Development-, and Auxin-Specific Regulation of Gibberellin 3β-Hydroxylase Gene Expression in Pea Fruit and Seeds

“…5B), seed PsGA3ox1 mRNA levels were maintained between 50 and 75 fg mg fresh weight Ϫ1 from 6 to 14 DAA, whereas seed GA 1 levels decreased to 20 ng g fresh weight Ϫ1 by 8 DAA and were minimally detectable by 12 DAA (Rodrigo et al, 1997 (Rodrigo et al, 1997), it is possible that GA 1 is synthesized through the early 13-hydroxylation pathway in developing pea seeds; however, using genetic and metabolic studies, an alternative hypothesis for GA 1 synthesis via GA 4 has been proposed. This model proposes that GA 4 is synthesized in the endosperm/ embryo (4 DAA) and transported to the testa, where it is 13␤-hydroxylated to GA 1 (Rodrigo et al, 1997;MacKenzie-Hose et al, 1998). However, conversion of GA 4 or other GA substrates to GA 1 in any seed tissues has not been demonstrated to date.…”

Recent advances in gibberellin biosynthesis

“…It would appear, therefore, that the GA-biosynthetic pathway is of ancient origin. 1995) and pea (Martin et al, 1996) favouring the nonhydroxylated substrate GA 12 , whereas those from rice With the exception of the pumpkin enzyme, all GA 20-oxidases that have been cloned catalyse the removal ( Toyomasu et al, 1997) and wheat (NEJ Appleford, JR Lenton, AL Phillips, and P Hedden, unpublished of C-20 as their major activity, with a small amount of information) have a higher or equal affinity for GA 53 . GA 20-oxidases, the 3b-hydroxylases are encoded by multi-gene families.…”

Methylation of Gibberellins by Arabidopsis GAMT1 and GAMT2

“…In pea (Pisum sativum), an active GA, GA 1 , is found in high levels in the seeds (4 to 7 d after anthesis) and at lower levels in the pod (MacKenzie-Hose et al, 1998). It has also been reported that exchange of hormones in the fruit between the pod and the seeds is necessary for proper seed development in P. sativum and that lack of sufficient levels of GAs in either the pod or in the embryo leads to seed abortion (Eeuwens and Schwabe, 1975;MacKenzie-Hose et al, 1998).…”