Local hopping mobile DNA implicated in pseudogene formation and reductive evolution in an obligate cyanobacteria-plant symbiosis.

摘要: Insertion sequences (ISs) are approximately 1 kbp long “jumping” genes found in prokaryotes. ISs encode the protein Transposase, which facilitates excision and reinsertion of genomes, making these a type class I (“cut-and-paste”) Mobile Genetic Elements. proposed to be involved reductive evolution symbiotic Our previous sequencing genome cyanobacterium ‘Nostoc azollae’ 0708, living tight perpetual association with plant (the water fern Azolla), revealed presence an eroding genome, high number insertion together unprecedented large proportion pseudogenes. To investigate role potentially formation pseudogenes, bioinformatic investigation IS identities positions 47 cyanobacterial genomes was conducted. widen scope, contents were analysed qualitatively quantitatively 20 other representing both free-living bacteria. Sequences not randomly distributed bacterial transpose short distances from their original location (“local hopping”) pseudogenes enriched vicinity elements. In general, organisms showed higher densities elements than non-symbiotic A total 1108 distinct repeated over 500 bp identified 67 investigated. apparent at 970 locations (14.3%), 428 being full-length. Morphologically complex cyanobacteria frequencies elements, irrespective life style. The co-location prokaryotic implies earlier transpositions into genes. As tend local rather wide this likely explains proximity between These findings suggest that facilitate for instance 0708 obligate symbionts.