Gibberellin Concentration and Transport in Genetic Lines of Pea

Abstract

Effects of the Na and Le loci on gibberellin (GA) content and transport in pea (Pisum sativum L.) shoots were studied. GA1, GA8, GA17, GA19, GA20, GA29, GA44, GA8 catabolite, and GA29 catabolite were identified by full-scan gas chromatography-mass spectrometry in extracts of expanding and fully expanded tissues of line C79-338 (Na Le). Quantification of GAs by gas chromatography-singleion monitoring using deuterated internal standards in lines differing at the Na and Le alleles showed that na reduced the contents of GA19, GA20, and GA29 on average to <3% and of GA1 and GA8 to <30% of those in corresponding Na lines. In expanding tissues from Na /e lines, GA1 and GA8 concentrations were reduced to approximately 10 and 2%, respectively, and GA29 content increased 2-to 3-fold compared with those in Na Le plants. There was a close correlation between stem length and the concentrations of GA1 or GA8 in shoot apices in all six genotypes investigated. In na/Na grafts, internode length and GA1 concentration of nana scions were normalized, the GA20 content increased slightly, but GA19 levels were unaffected. Movement of labeled GAs applied to leaves on Na rootstocks indicated that GA19 was transported poorly to apices of na scions compared with GA20 and GA1. Our evidence suggests that GA20 is the major transported GA in peas.Considerable evidence points to GA12 as the native GA controlling internode elongation in a number of plant species, including pea (Pisum sativum L.) (11,15,24,29,30). GA1 is synthesized via the 13-hydroxylation pathway, in which GA12 is 13-hydroxylated to GA53, which is then converted successively to GA44, GA19, and GA20. GA20 is either 23-hydroxylated to GA29 or 3,3-hydroxylated to GA1, which in turn is metabolized to GA8. The 2,B-hydroxylated GAs, GA8 and GA29, are oxidized further at C-2 in pea to give the respective catabolites (11,28). Of these compounds, only GA1 is thought to be active in controlling stem elongation (18). Mutant alleles in several species block GA biosynthesis, resulting in dwarf phenotypes (5,24,29,30). In pea, 12 loci are known to influence plant stature (21) and recessive alleles at four of these reduce GA, biosynthesis (9, 11, 23). The le locus results in reduced conversion of GA20 to GA, (11,12), the na allele is thought to block ent-7a-hydroxykaurenoic acid conversion to GA12-aldehyde, and the Ih and ls alleles apparently affect the conversion of geranylgeranyl Pi to entkaurene (9). Genetic evidence indicates that all of these loci are 'leaky' (20). The quantitative effects of different Le alleles on GA, and GA8 concentrations have been studied previously with differing conclusions (6,10,(25)(26)(27). Whereas similar (6, 27) levels of GA1 were reported in shoots of Progress No. 9 (lele) compared with the nonisogenic Alaska (LeLe), in isogenic plants differing at the Le locus the dwarf genotype produced 10-to 20-fold less GA1 and GA8 than the tall genotype (10,25,26).Recognition of the importance of GA1 in stem elongation and identification of the sites of ...

Gibberellic acid in plant

“…4,5 The transport of active GAs and their intermediates was supported by grafting experiments . 6,7,8 The contradictory results obtained from different experiments could not pin-point the site of synthesis of bioactive GA. Gibberellins being synthesized via the terpenoid pathway, require 3 enzymes viz., terpene synthase (TPSs), cytochrome P450 mono-oxygenase (P450s) and 2-oxoglutarate dependent dehydrogenase (2 ODDs), for the biosynthesis of bioactive GA from GGDP in plants (Fig. 1).…”

Differences in Root Growth and Permeability in the Grafted Combinations of Dutch Tomato Cultivars (Starbuck and Maxifort) and Japanese Cultivars (Reiyo, Receive, and Magnet)

“…Grafting is widely established in agriculture and provides practical advantages for vegetable production by increasing resistance to soilborne pathogens [1]- [4], tolerance to low root-zone temperatures [5]- [7], salinity tolerance [8]- [10], and endogenous hormone production [11]- [13]. In particular, increased salinity tolerance improves fruit yield of grafted tomato [8] [14].…”

Ovary-derived precursor gibberellin A9 is essential for female flower development in cucumber

“…Similarly, Proebsting et al (1992) reported that the biologically inactive precursor GA 20 , a product of the GA 20-oxidase, is the major transported GA from leaves to apices in pea.…”