An altered constitutive peptide in sym 5 mutants of Pisum sativum L.

Mutational analysis of Pisum sativum L. was used to search for constitutive proteins that might function in nodule formation. The sym 5 locus is a mutational hot spot, represented by seven independently derived mutant lines with decreased nodulation. Comparison of two-dimensional polyacrylamide gels of in vitro-translated root RNA showed a consistent difference in the migrational pattern of one peptide. In the nodulating parental cultivar Sparkle, a 66 kDa peptide had a pI of 5.9. In four of the five tested sym 5 mutants, the 66 kDa peptide had a more acidic pI of 5.8. This 66 kDa peptide is found in lateral root, tap root, and shoot. Its expression was independent of rhizobial inoculation, root temperature, or light.