Saleheh Ebadirad - Space Biology and Astrobiology Research Network (SBARN), Universal Scientific Education and Research Network
Morteza Hadizadeh - Space Biology and Astrobiology Research Network (SBARN), Universal Scientific Education and Research Network
Mohammad Fazel Soltani - Department of Crop Production and Plant Breeding, College of Agriculture, Razi University
Razieh Abdilzadeh - Department of Biology, Faculty of Sciences, Ferdowsi University of Mashhad

Tardigrades or water bears that are micro eukaryotic species can tolerate extreme environments in comparison with other known living organisms. They can survive in unusual temperatures (Nearly -273 ˚C up to more than 100 ˚C), high pressures (up to 7.5 GPa), gravitational changes, dehydration, exposure to high doses of radiation immersed in organic solvents as well as exposure to open space directly [1]. The fundamental mechanisms behind tardigrades’ survival are not understood completely. One of the most significant molecular points of view about their great functionality could be related to Heat shock proteins (HSPs) that are an important subgroup of chaperones. HSPs take part in proteins’ protection and have a notable role in their irreversible aggregation and degradation. While confronting environmental stresses, tardigrades express HSPs in order to respond to the extreme condition efficiently[2]. HSP90 is one of the most common forms of HSPs[3]. In this study, 13 protein sequences of HSP90 related to Tardigrada and principal animal classes were extracted from the UniProt website and then analyzed with Gene Infinity and Minitab v.16 software (one sequence from Ramazzottius varieornatus, that is considered among the hardiest kinds of the tardigrades, and 12 sequences from other classes’ chosen species). The obtained results show that the least codon usage similarity between targeted species belongs to Tardigrada (0%). Altogether it can be concluded that Tardigrada has specific genetic characteristics as its unique codon usage that distinguishes this class from other animal classes. Tardigrada genome is almost completely unique and several genome sequences allow them to survive harsh conditions may have external origins. Due to some studies, it is found that there are some external genes in tardigrade s genome that may be the result of horizontal gene transfer (HGT)[1 & 4].

Tardigrada, HSP90; Bioinformatics; Exteremophile; Space Biology