title: Internode length in Pisum : The Le gene controls the 3β-hydroxylation of gibberellin A20 to gibberellin A 1.
abstract: The influence of the Na and Le genes in peas on gibberellin (GA) levels and metabolism were examined by gas chromatographic-mass spectrometric analysis of extracts from a range of stem-length genotypes fed with [(13)C, (3)H]GA20. The substrate was metabolised to [(13)C, (3)H]GA1, [(13)C, (3)H]GA8 and [(13)C, (3)H]GA29 in the immature, expanding apical tissue of all genotypes carrying Le. In contrast, [(13)C, (3)H]GA29 and, in one line, [(13)C, (3)H]GA29-catabolite, were the only products detected in plants homozygous for the le gene. These results confirm that the Le gene in peas controls the 3β-hydroxylation of GA20 to GA1. Qualitatively the same results were obtained irrespective of the genotype at the Na locus. In all Na lines the [(13)C, (3)H]GA20 metabolites were considerably diluted by endogenous [(12)C]GAs, implying that the metabolism of [(13)C, (3)H]GA20 mirrored that of endogenous [(12)C]GA20. In contrast, the [(13)C, (3)H]GA20 metabolites in na lines showed no dilution with [(12)C]GAs, confirming that the na mutation prevents the production of C19-GAs. Estimates of the levels of endogenous GAs in the apical tissues of Na lines, made from the (12)C:(13)C isotope ratios and the radioactivity recovered in respective metabolites, varied between 7 and 40 ng of each GA per plant in the tissue expanded during the 5 d between treatment with [(13)C, (3)H]GA20 and extraction. No [(12)C]GA1 and only traces of [(12)C]GA8 (in one line) were detected in the two Na le lines examined. These results are discussed in relation to recent observations on dwarfism in rice and maize.
authors.affiliation: Department of Botany, University of Tasmania, 7001, Hobart, Tasmania, Australia.
authors.forename: T J
authors.initials: TJ
authors.lastname: Ingram
authors.forename: J B
authors.initials: JB
authors.lastname: Reid
authors.forename: I C
authors.initials: IC
authors.lastname: Murfet
authors.forename: P
authors.initials: P
authors.lastname: Gaskin
authors.forename: C L
authors.initials: CL
authors.lastname: Willis
authors.forename: J
authors.initials: J
authors.lastname: Macmillan