Comparative genomics in phytopathogenic prokaryotes reveals the higher relative abundance and density of long-SSRs in the smallest prokaryotic genome.

Frequency and distribution of long-SSRs were studied in 18 phytopathogenic prokaryotes. Higher relative abundance of the long-SSRs was observed in phytopathogenic prokaryotes when compared to non-pathogenic control. The frequency of these SSRs was positively correlated with size and GC content of the genomes of phytopathogenic prokaryotes. Interestingly, phytopathogens with higher GC content in the genome were found to posses longer repeat motifs of SSRs, whereas those having lesser GC content were harbouring shorter repeat motifs. Higher abundance of tri- and hexa-nucleotide repeat motifs were the characteristic of actinomycetes, where as higher abundance of mono- and tetra-nucleotide repeats were the characteristic of the mollicutes. The maximum relative abundance and relative density of SSR were found in the smallest genome of host-adapted pathogen Aster yellow, however, length of microsatellite repeat units was the least. On the basis of presence of SSRs in the housekeeping genes, a phylogenetic relationship between these phytopathogenic prokaryotes was deduced and compared with the phylogeny developed based on 16S ribosomal RNA gene.

A comparative survey of microsatellites among wild and domestic cat provides valuable resources for marker development.

Information on the level and distribution of genetic variation is important for conservation plan of captive population of an endangered species such as tiger and cheetah. We assayed the frequency of microsatellites in the genomic and genic sequences of wild cats (Panthera tigris, Acinonyx jubatus) and compared it with the domestic cat (Felis catus). Frequency, relative abundance and density of microsatellites were highest in the domestic cat when compared with wild cats. The frequency of microsatellites was positively correlated with the G+C content of genomic and genic sequences. The maximum frequency of microsatellites among all three sequence sets was of di-nucleotide repeats (genomic-88.1%; genic-70.4%), whereas the hexa-nucleotide repeat represents < 0.5%. Motif conservation study among the genomic and genic sequences revealed conservation of 81.3% and 51.0% motif within the members of family Felidae. A total 40,233 primers from genic sequences were designed in order to enrich the members of family Felidae with genomic resources. The designed primers could be useful in determining the molecular genetics of population structure and individualization of a particular cat.

Microsatellite repeat dynamics in mitochondrial genomes of phytopathogenic fungi: frequency and distribution in the genic and intergenic regions.

The frequency and distribution of microsatellites were analyzed in the 19 mitogenomes of phytopathogenic fungi covering five phyla. Our analysis revealed that in all the mitogenomes studied, the frequency and relative abundance varied, and it was neither influenced by genome size nor by GC content. SSRs were found to be differential distributed in genic and intergenic regions. An average of 5.14 (23.6%) SSRs were present in genic sequences and 21.7 (76.4%) SSRs were located in the intergenic sequences. Relative abundance of SSRs in mitogenomes was the highest in Aspergillus tubigensis, whereas, it was the least in Phaeosphaeria nodurum, the average being 0.45. Trinucleotide repeats were the most abundant motifs in the genic and intergenic regions of the mitogenomes of the phytopathogenic fungi. Among the genes, cox1 harbors the maximum SSRs, whereas cox3 and nad 7 contain the least. Based on the presence of SSRs in a particular gene, genetic relationships among individual organisms were also established.