Hsp70

Salmon must deal with many stressors such as high water temperatures, changes in water salinity, toxins, hypoxia, and disease (Nover 1991, Volker et al. 1992, Forsyth et al. 1997, DuBeau et al. 1998, Iwama et al. 1998). In response to stressors that cause denaturation of proteins, heat shock proteins (hsps) are produced. Hsps are also called stress proteins because they are produced in response to stressors other than heat (Iwama et al. 1998). Overall, there are three groups of hsps: hsp90, hsp70, and low molecular weight hsp (Basu et al. 2002). Hsp70 is involved with maintenance of proteins by repairing denatured proteins or translocating permantly damaged proteins to lysosomes and proteosomes (Kiang and Tsokos 1998, Lund et al. 2002).

Orthologs

Each species investigated was generally most related to other species within their taxonomic groups by Kingdom, and the patterns were almost identical between the tree produced with nucleotides and the three produced by proteins. The mammals (dog, norway rat, human, yak), the fishes (carp, goldfish, salmonids, sea bass, medaka, killifish, zebrafish, and olive flounder), and invertebrates (bay scallop, tiger prawn, Asian lady beetle, and silk moth) were grouped together within each of their taxanomic groups. Curiously, the amphibians (Xenopus sp. and mole salamander) were not grouped together. In the tree produced with nucleotides, the Xenopus sp. was most similar to the coelocanth, and the mole salamander was most similar to the invertebrates. In the tree produce with proteins, Xenopus sp. was most closely related to mammals, and again the mole salamander was most similar to invertebrates. Yeast and wild carrot were most dissimilar to all other animals.

Within the teleosts, the salmonids (rainbow trout, chinook salmon, Atlantic salmon) and cyprinids (carp and goldfish) were grouped within their taxanomic group by Family. Killifish, medaka, and seabass were grouped together, and zebrafish was grouped with the cyprinids. Olive flounder was the most distinct of all other fishes. Again, the patterns of the tree produced with nucleotides were almost identical to those in the tree produced with proteins.

Paralogs

In the tree produced with nucleotides, the complete gene sequence of hsp70 and the partial sequence were most similar to each other. Hsp70a and hsp70b were most similar to each other, and the clone of hsp70 was most similar to these. Heat shock cognate protein (hsc) 71 kDa and hsc70A were most similar to each other, and hsc70B was most similar to these. Heat shock cognate proteins are in the family of molecular chaperones and has the ability to induce cytotoxic T lymphocytes (Azuma et al. 2003).

In the tree produced with proteins, the different versions of hsp70 proteins (AAA49562.1, BAB72233.1, BAD83574.1, BAD83575.1) were grouped together, except for AAA49563.1. This was most closely similar to the glucose-related 78 kDa protein (BAD90025.1), which thus raises the AAA49563.1 sequence to be questionable. The two hsp70 8 isoform (a & b) and hsc 71 kDa were grouped together and most dissimilar for the group of hsp70 proteins.

Evolution

Hsp70 generally served well as a nucleotide or protein sequence to determine the relatedness among species. For example, the hsp70 protein most likely evolved in the common ancestor to the four animals investigated in this project; and thus the hsp70 nucleotide or protein sequences, although not identical, were most similar to each other among the four mammals.