Phylogenetic analysis of HSP70 gene of Aspergillus fumigatus reveals conservation intra-species and divergence inter-species

Aspergillus fumigatus is a saprophyte fungus, widely spread in a variety of ecological niches and the most prevalent aspergilli responsible for human and animal invasive aspergillosis. The first step to develop novel and efficient therapies is the identification and understanding of the key tolerance and virulence factors of pathogens. The main focus of the present study is to perform the similarity, conservation and phylogenetic analysis of heat shock protein 70 (HSP70) gene of the fungus A. fumigatus. Therefore, DNA sequence of HSP70 gene was obtained from a native airborne A. fumigatus. Similarity, divergence and conservation of HSP70 gene sequence were assayed and compared to other strains and fungal species using nucleotide Basic Local Alignment Search Tool (BLAST), construction of phylogenetic tree and online analysis tools. The results revealed that the most similar aspergilli to the examined A. fumigatus strain were A. fumigatus non-native strains, Aspergillus clavatus, Aspergillus niger, Aspergillus terreus, and Aspergillus nidulans. Among other fungal genera, Penicillium species were the most similar fungal genus to A. fumigatus. Moreover, the alignment results revealed high levels of similarity and conservation of native A. fumigatus HSP70 gene sequence with yeasts stress-Seventy subfamily A (SSA) gene sequence from HSP70 family of genes and lower similarities with other genes in the family (Ssb, Ssc, HscA, Kar2 and bipA). Penicillium spp. were the most similar fungi to Aspergillus species by phylogenetic analysis of HSP70 sequence. Other molds, yeasts and yeast-like fungi were placed in more distanced clades. In general, fungal HSP70 sequence analysis could direct us to make a better understanding of thermo-tolerance in different fungal species.