Abstract
In the present paper, we report for the first time the characterization of llama (Lama glama) caseins at transcriptomic and genetic level. A total of 288 casein clones transcripts were analysed from two lactating llamas. The most represented mRNA populations were those correctly assembled (85.07%) and they encoded for mature proteins of 215, 217, 187 and 162 amino acids respectively for the CSN1S1, CSN2, CSN1S2 and CSN3 genes. The exonic subdivision evidenced a structure made of 21, 9, 17 and 6 exons for the αs1-, β-, αs2- and κ-casein genes respectively. Exon skipping and duplication events were evidenced. Two variants A and B were identified in the αs1-casein gene as result of the alternative out-splicing of the exon 18. An additional exon coding for a novel esapeptide was found to be cryptic in the κ-casein gene, whereas one extra exon was found in the αs2-casein gene by the comparison with the Camelus dromedaries sequence. A total of 28 putative phosphorylated motifs highlighted a complex heterogeneity and a potential variable degree of post-translational modifications. Ninety-six polymorphic sites were found through the comparison of the lama casein cDNAs with the homologous camel sequences, whereas the first description and characterization of the 5’- and 3’-regulatory regions allowed to identify the main putative consensus sequences involved in the casein genes expression, thus opening the way to new investigations -so far- never achieved in this species.
Highlights
The Andean highlands, especially the Altiplano of southeast Peru and western Bolivia, is the natural habitat of South American camelids
The most represented populations for each of the gene transcripts were those correctly assembled. They encoded for mature proteins of 215, 217, 187 and 162 amino acids respectively for the CSN1S1, CSN2, CSN1S2 and CSN3 genes
The homologous genes in dromedary camel encode for casein of the same length with the only exception of the CSN1S2, which gives an αs2-casein of 178 amino acids (9 residues shorter than llamas) [15], whereas compared to cattle, the llamas casein show a higher number of amino acids for the αs1-CN (215 vs 199 aa) and β-CN (217 vs 209 aa), and lower length for the αs2-CN (187 vs 207 aa) and κ-CN (162 vs 169 aa)
Summary
The Andean highlands, especially the Altiplano of southeast Peru and western Bolivia, is the natural habitat of South American camelids (llama, guanaco, alpaca and vicuna). These species belong to Camelidae family (together with dromedary, bactrian and wild bactrian camels) and they are members of Lamini tribe, which originated in North America during the Eocene about 40–50 Ma ago [1]. Llamas (Lama glama) are kept as a multipurpose animals. Their valuable fleece are obtained by shearing their coarse wool [2], whereas for PLOS ONE | DOI:10.1371/journal.pone.0124963. The text of the manuscript was updated by the link to the corresponding NCBI webpages
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