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Plant Physiology Preview Published on November 16, 2007; 10.1104/pp.107.111369
OPEN ACCESS ARTICLE
Received October 19, 2007 Combined metabolomic and genetic approaches reveal a link between the polyamine pathway and albumin 2 in developing pea seeds
Max-Planck Institute of Molecular Plant Physiology, Am Muhlenberg 1, 14476 Golm, Germany; John Innes Centre, Norwich Research Park, Colney, Norwich, NR4 7UH, UK; Pharmacy Department, Bradford University, Pharmaceutical Chemistry Section, Bradford BD7 1DP, UK * Corresponding author; email: geigenberger{at}mpimp-golm.mpg.de.
Several legume seed proteins that are potentially allergenic, poorly digested by farm animals, and/or have undesirable functional properties, have been described. One of these is the albumin protein in pea (Pisum sativum L.) called PA2. A naturally occurring mutant line that lacks PA2 has been exploited in studies to determine the biological function of this non-storage protein in seed development. The mutant, which has a small seed, a tall plant phenotype, and lacks most of the PA2-encoding genes, has been crossed with a standard cultivar (cv.) Birte that contains PA2 to give rise to a recombinant inbred (RI) population. An F3 line carrying the mutation, and having a short plant phenotype, has been used to generate back-cross (BC) lines with the cv. Birte. Despite having a lower albumin content, seeds from the mutant parent and RI lines lacking PA2 have an equivalent or higher seed nitrogen content. Metabolite profiling of seeds revealed major differences in amino acid composition and polyamine content in the two parent lines. This was investigated further in BC lines, where the effects of differences in seed size and plant height between the two parents were eliminated. Here, differences in polyamine synthesis were maintained as was a difference in total seed protein between the BC line lacking PA2 and cv. Birte. Analysis of enzyme activities in the pathways of polyamine synthesis revealed that the differences in spermidine content were attributable to changes in the overall activities of spermidine synthase and arginine decarboxylase. Although the genes encoding spermidine synthase and PA2 both localised to the pea linkage group I, the two loci were shown not to be closely linked and to have recombined in the BC lines. A distinct locus on linkage group III contains a gene that is related to PA2 but expressed predominantly in flowers. The results provide evidence for a role of PA2 in regulating polyamine metabolism, which has important functions in development, metabolism and stress responses in plants.
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