The evolutionary puzzle solution for the origins of the partial loss of the Cτ2 exon in notothenioid fishes

Comparative Analysis of the pIgR Gene from the Antarctic Teleost Trematomus bernacchii Revealed Distinctive Features of Cold Adapted Notothenioidei

“…Two (in P. georgianus) or three (in G. acuticeps) pIgR transcripts, referred to as variant X1, variant X2 and variant X3, had been annotated in the respective genome assemblies (Figure 6). As previously shown by the AT content analysis of notothenioid IgT genes [21], most interestingly, a remarkably high AT content of pIgR exons was shared within Antarctic species, reaching a peak (55.8 %) in the family Nototheniidae, which comprises T. bernacchii and Dissostichus eleginoides (Figure 7). This finding reflects a peculiar feature neither shared with the non-Antarctic species C. gobio, their closest relative, nor with all the other Perciformes.…”

“…To our knowledge this finding is not surprising. Previous studies we conducted on the Ig heavy chain gene locus of Notothenioidei revealed peculiar rearrangements of the intronic regions of both IgM and IgT heavy chain genes [21,42].…”

“…Glycosylation can also modulate a correct balance between protein solubility and structural flexibility. This role can be viewed as a special adaptive response to cold environment, such as in the case of Antarctic fish IgT and IgM, found to be highly glycosylated [21,47]. A further element that indicates an increase in solubility is related to the greater surface electrostatic charge.…”

“…This taxonomic group has long been considered an attractive model to study biochemical, physiological and morphological adaptations, although poorly investigated at a molecular level. In previous studies, we investigated the genes encoding IgM and IgT isotypes in several cold-adapted and temperate notothenioid species [19][20][21] and highlighted the first evidence for a possible hepato-biliary transport of Ig in the Antarctic species Trematomus bernacchii [22].…”

Comparative Analysis of the pIgR Gene from the Antarctic Teleost Trematomus bernacchii Reveals Distinctive Features of Cold Adapted Notothenioidei

“…This taxonomic group has long been considered an attractive model to study biochemical, physiological and morphological adaptations, although poorly investigated at a molecular level. In previous studies, we investigated the genes encoding IgM and IgT isotypes in several cold-adapted and temperate notothenioid species [19][20][21] and highlighted the first evidence for a pos-sible hepato-biliary transport of Ig in the Antarctic species Trematomus bernacchii [22]. The most recent advances in collecting omics data from notothenioid fish provided a source of fundamental information about molecular and genetic features, allowing conduct of also evolutionary studies on notothenioids in comparison with other perciform species.…”