Molecular analysis of a null mutant for pea (Pisum sativum L.) seed lipoxygenase-2

A mutant line of Pisum fulvum was identified that lacked seed lipoxygenase- 2 (LOX-2). The mutant phenotype was introgressed into a standard Pisum sati vum cv. Birte to provide near-isogenic lines with or without seed LOX-2. Ge netic analyses showed the mutation to behave as a single, recessive Mendeli an gene. Northern and dot-blot analyses showed a large reduction in LOX-2 m RNA from developing seeds of the LOX-2-null mutant. A restriction fragment length polymorphism associated with the 5' end of the LOX-2 gene(s) co-segr egated with the null phenotype, indicating that the reduction of LOX-2 mRNA was neither a consequence of deletion of the LOX genes nor a consequence o f the action of a genetically distant regulatory gene. Analysis of the 5'-f lanking sequences of LOX-2 genes from Birte and the near-isogenic LOX-2-nul l mutant revealed a number of insertions, deletions and substitutions withi n the promoter from the LOX-2-null mutant that could be responsible for the null phenotype. Incubation of crude seed LOX preparations from Birte and t he LOX-2-null mutant showed that the latter generated relatively less 13-hy droperoxides and also produced relatively more hydroxy- and ketoacid compou nds that have implications for the fresh-frozen pea industry.