engleski

SSB protein genes in the genomes of bacteria from the genus 'Candidatus Phytoplasma' and their potential role in genome instability

Insect-transmitted phytopathogenic bacteria from the genus ‘Candidatus Phytoplasma’ have small genomes that experienced specific gene losses and gains through their dynamic co-evolution with plant and insect hosts. In spite of being small and reduced, their genomes are repeat-rich and contain multicopy genes. One of those multicopy genes is the ssb gene. SSB proteins, essential for cell survival, are found in all domains of life and viruses. In phytoplasma genomes, SSB protein genes may be present in different numbers with only one ssb gene with different evolutionary origin located in a specific genomic neighbourhood. In this study, all ssb gene sequences available from sequenced phytoplasma genomes were analyzed together with the “original” ssb gene amplified and sequenced from a number of 'Ca. P. asteris' and 'Ca. P. solani' isolates. Phylogenetic analyses have shown that all the “original” ssb genes from different phytoplasma species clustered together. Unlike the other shorter ssb gene copies of undetermined functionality, the only ssb gene copy from 'Ca. P. mali' genome was phylogenetically closer to the “original” ones which was in accordance with its' different genome organization and stability. Southern blot analyses have confirmed the presence of one “original” ssb gene in the genomes of ‘Ca. P. asteris’. Surprisingly, in the genome of ‘Ca. P. solani’ isolate, another copy of the “original” ssb gene was repeatedly detected suggesting that it could be a part of extrachromosomal element characteristic of the species which is known to possess the largest and supposedly the most unstable genome among all phytoplasmas.

AY; genome; instability; phytoplasma; stolbur; ssb

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