No abstract

We have isolated and sequenced the genes encoding the heat shock proteins 60 (Hsp60) and 70 (Hsp70) of the salmon pathogen Piscirickettsia salmonis. The sequence analysis revealed the expected two open reading frames that encode proteins with calculated molecular weights of 60,060 and 70,400. The proteins exhibit a 70-80% homology with other known prokaryotic Hsp60 and Hsp70 sequences. The coding regions have been expressed in E. coli as thioredoxin fusion proteins. Both recombinant proteins were shown to elicit a humoral response when injected intraperitoneally in Atlantic salmon and also conferred protection to fish challenged with P. salmonis. The present data will facilitate further studies on the involvement of heat shock proteins in protective immunity of fish to infection by P. salmonis and their potential use in recombinants vaccines against this intracellular pathogen.

Northern-blot analysis of RNAs from different tissues demonstrated that the mRNA for the protein kinase CK2a subunit is very abundant in the ovary of Xenopus luevis. The competitive reverse-PCR technique has been used to quantitate the mRNA for both CK2a and CK2p subunits during oogenesis. The results obtained using eight different animals consistently show an increment of 2-3-fold in the mRNA for both subunits in vitellogenic oocytes (stages 11-VI). Each stage-VI oocyte contains approximately 5XIO-' molecules CK2a mRNA and 1 XIO-' molecules CK2p mRNA. These amounts are considerably higher than many other mRNAs analyzed in these cells. Activity measurements of CK2 using casein or a specific model peptide revealed increments of about 10-12-fold during oogenesis, and also indicated that the amount of enzyme in the nucleus accounted for 15530% of the total enzyme in the oocyte at all stages. Western-blot analysis of CK2a indicated that the amount of this protein subunit also increased during oogenesis in a parallel fashion with the increment of enzymic activity.

Northern‐blot analysis of RNAs from different tissues demonstrated that the mRNA for the protein kinase CK2α subunit is very abundant in the ovary of Xenopus laevis. The competitive reverse‐PCR technique has been used to quantitate the mRNA for both CK2α and CK2β subunits during oogenesis. The results obtained using eight different animals consistently show an increment of 2–3‐fold in the mRNA for both subunits in vitellogenic oocytes (stages II‐VI). Each stage‐VI oocyte contains approximately 5 × 10−7 molecules CK2α mRNA and 1 × 10−7 molecules CK2β mRNA. These amounts are considerably higher than many other mRNAs analyzed in these cells. Activity measurements of CK2 using casein or a specific model peptide revealed increments of about 10–12‐fold during oogenesis, and also indicated that the amount of enzyme in the nucleus accounted for 15–30% of the total enzyme in the oocyte at all stages. Western‐blot analysis of CK2α indicated that the amount of this protein subunit also increased during oogenesis in a parallel fashion with the increment of enzymic activity.

The complete sequence of the mitochondrial genome of Chinook salmon, Oncorhynchus tshawytscha, has been determined. The circular genome consisting of 16,644 base pairs encodes thirteen proteins, the 12S and 16S ribosomal RNAs, and 22 transfer RNAs. These genes are ordered in the same way as most other vertebrates. The nucleotide and amino acid sequences of the ribosomal RNAs and the thirteen protein-coding genes were compared with those of other salmonids such as Oncorhynchus mykiss, Salmo salar, Salvelinus fontinalis, Salvelinus alpinus and Coregonus lavaretus. The sequence features of the control region (D-loop), the origin of L-strand replication and a putative peptide codified by the 16S mitochondrial RNA are described and discussed.