Open AccessChloroplast gene sequence data suggest a single origin of the predisposition for symbiotic nitrogen fixation in angiosperms.
Author(s) -
Douglas E. Soltis,
Pamela S. Soltis,
David R. Morgan,
Susan M. Swensen,
Beth C. Mullin,
JM Dowd,
Peter Martin
Publication year - 1995
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.92.7.2647
Subject(s) - biology , nitrogen fixation , phylogenetic tree , clade , fixation (population genetics) , lineage (genetic) , actinorhizal plant , chloroplast dna , gene , phylogenetics , genetics , botany , symbiosis , evolutionary biology , dna sequencing , root nodule , bacteria
Of the approximately 380 families of angiosperms, representatives of only 10 are known to form symbiotic associations with nitrogen-fixing bacteria in root nodules. The morphologically based classification schemes proposed by taxonomists suggest that many of these 10 families of plants are only distantly related, engendering the hypothesis that the capacity to fix nitrogen evolved independently several, if not many, times. This has in turn influenced attitudes toward the likelihood of transferring genes responsible for symbiotic nitrogen fixation to crop species lacking this ability. Phylogenetic analysis of DNA sequences for the chloroplast gene rbcL indicates, however, that representatives of all 10 families with nitrogen-fixing symbioses occur together, with several families lacking this association, in a single clade. This study therefore indicates that only one lineage of closely related taxa achieved the underlying genetic architecture necessary for symbiotic nitrogen fixation in root nodules.