Retraction for Yang et al., Y4lO of Rhizobium sp. Strain NGR234 Is a Symbiotic Determinant Required for Symbiosome Differentiation.

Volume 191, no. 3, p. 735–746, 2009. In the original article describing the symbiotic phenotype of the mutant NGR y4lO, we concluded that observed impaired symbiosome differentiation and nitrogen fixation were due to a mutation in the nopJ (formerly y4lO) gene, suggesting a role for nopJ in symbiosome differentiation in host cells of leguminous nodules. In response to a contradictory report by Kambara et al. (K. Kambara, S. Ardissone, H. Kobayashi, M. M. Saad, O. Schumpp, W. J. Broughton, and W. J. Deakin, Mol. Microbiol. 71:92–106, 2009), we shotgun sequenced the genome of NGR y4lO and found a 31.9-kb deletion in the symbiotic replicon. Confirmation of this spontaneous deletion by PCR and phenotypes of two additional nopJ knockout mutants have led us to conclude that the observed phenotype of NGR y4lO described in the original paper is due to the deletion of nitrogen fixation (nif) genes rather than to knockout of the nopJ gene. We regret that retraction of this article is necessary and apologize for any inconvenience caused.