RESTRICTION OF HOST-RANGE BY THE SYM2 ALLELE OF AFGHAN PEA IS NONSPECIFIC FOR THE TYPE OF MODIFICATION AT THE REDUCING TERMINUS OF NODULATION SIGNALS

Rhizobium leguminosarum by. viciae strains producing lipo-chitin oligo saccharides (LCOs) that are O-acetylated at the reducing terminus are required for nodulation of wild pea cultivars originating from Afghani stan that possess the recessive sym2(A) allele, The O-acetylation of t he reducing sugar of LCOs is mediated by the bacterial nodX gene, whic h presumably encodes an acetyltransferase. We found that for nodulatio n on Afghan pea cultivars and sym2(A) introgression lines the nodX gen e can be functionally replaced by the nodZ gene of Bradyrhizobium japo nicum, which encodes a fucosyltransferase that fucosylate the reducing terminus of LCOs, The structure of the nodules, which were induced wi th normal frequency, was typical for effective pea nodules, and they f ixed nitrogen with the same efficiency as nodules induced by nodX-carr ying strains.