Abstract
AbstractTumorigenic members of the familyRhizobiaceae, known as agrobacteria, are responsible for crown and cane gall diseases of various agricultural crops worldwide. Tumorigenic agrobacteria are commonly found in the generaAgrobacterium,Allorhizobium, andRhizobium. In this study, we analyzed a distinct “tumorigenes” clade of the genusRhizobium, which includes the tumorigenic speciesRhizobium tumorigenes, as well as strains causing crown gall disease on rhododendron. Here, high quality, closed genomes of representatives of the “tumorigenes” clade were generated, followed by comparative genomic and phylogenomic analyses. Additionally, phenotypic characteristics of representatives of the “tumorigenes” clade were analyzed. Our results showed that the tumorigenic strains isolated from rhododendron represent a novel species of the genusRhizobiumfor which the nameRhizobium rhododendrisp. nov. is proposed. This species also includes additional strains originating from blueberry and Himalayan blackberry in USA, whose genome sequences were retrieved from GenBank. BothR. tumorigenesandR. rhododendricontain multipartite genomes, including a chromosome, putative chromids, and megaplasmids. Synteny and phylogenetic analyses indicated that a large putative chromid ofR. rhododendriresulted from the cointegration of an ancestral megaplasmid and two putative chromids, following its divergence fromR. tumorigenes. Moreover, gene clusters specific for both species of the “tumorigenes” clade were identified, and their biological functions and roles in ecological diversification ofR. rhododendriandR. tumorigeneswere predicted and discussed.
Publisher
Cold Spring Harbor Laboratory