Isolation and Characterization of a Pea Pod CDNA-Encoding a Putative Blue Copper Protein Correlated with Lignin Deposition

Nearly isogenic pea lines were selected to investigate the genetic basis for lignification of the pea (Pisum sativum) pod endocarp. The development of the pod endocarp in the normal and mutant pea pod phenotypes was examined by light microscopy. A pea pod cDNA library representing poly (A)(+) RNA purified from L59 plea pods (genotype, PV; phenotype, lignified endocarp) was differentially screened with total cDNA probes prepared from total pod RNA from L59 and L1390 (genotype, pv; phenotype, no lignification of endocarp) pods 4-6 d after flowering (DAF). A clone, designated pLP18, was selected for further characterization on the basis of hybridization to the L59 cDNA probe, but not the L1390 cDNA probe. Northern blotting was used to show that pLP18 represented a mRNA of 0.95 kb. The predicted polypeptide from the LP18 cDNA encoded a putative blue type 1 copper protein. The expression pattern of LP18 mRNA in pods of the experimental pea lines was determined using RT-PCR quantitation. Hybridization of the cDNA to pea genomic DNA showed that this protein is probably encoded by a single gene.