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.