RESUMO
Sinorhizobium fredii HH103 is a fast-growing rhizobial strain infecting a broad range of legumes including both American and Asiatic soybeans. In this work, we present the sequencing and annotation of the HH103 genome (7.25 Mb), consisting of one chromosome and six plasmids and representing the structurally most complex sinorhizobial genome sequenced so far. Comparative genomic analyses of S. fredii HH103 with strains USDA257 and NGR234 showed that the core genome of these three strains contains 4,212 genes (61.7% of the HH103 genes). Synteny plot analysis revealed that the much larger chromosome of USDA257 (6.48 Mb) is colinear to the HH103 (4.3 Mb) and NGR324 chromosomes (3.9 Mb). An additional region of the USDA257 chromosome of about 2 Mb displays similarity to plasmid pSfHH103e. Remarkable differences exist between HH103 and NGR234 concerning nod genes, flavonoid effect on surface polysaccharide production, and quorum-sensing systems. Furthermore a number of protein secretion systems have been found. Two genes coding for putative type III-secreted effectors not previously described in S. fredii, nopI and gunA, have been located on the HH103 genome. These differences could be important to understand the different symbiotic behavior of S. fredii strains HH103, USDA257, and NGR234 with soybean.
Assuntos
Genoma Bacteriano , Glycine max/microbiologia , Sinorhizobium fredii/genética , Genes Bacterianos , Dados de Sequência Molecular , Fixação de Nitrogênio/genética , Raízes de Plantas/microbiologia , Polissacarídeos Bacterianos/genética , Percepção de Quorum , Sinorhizobium fredii/fisiologia , Simbiose/genéticaRESUMO
We report draft genome sequences of three Mexican Erwinia amylovora strains. A novel plasmid, pEA78, was identified. Comparative genomics revealed an rpsL chromosomal mutation conferring high-level streptomycin resistance in two strains. In the effector gene avrRpt2, a single nucleotide polymorphism was detected that overcomes fire blight disease resistance in Malus × robusta 5.