Inducible galectins are expressed in the inflamed pharynx of the ascidian Ciona intestinalis.

Abstract Although ascidians belong to a key group in chordate phylogenesis, amino acid sequences of Ciona intestinalis galectin-CRDs ( Ci Lgals-a and -b) have been retained too divergent from vertebrate galectins. In the present paper, to contribute in disclosing Bi-CRD galectin evolution a novel attempt was carried out on Ci Lgals-a and -b CRDs phylogenetic analysis, and their involvement in ascidian inflammatory responses was shown. Ci Lgals resulted aligned with Bi-CRD galectins from vertebrates ( Xenopus tropicalis , Gallus gallus , Mus musculus , Homo sapiens ), cephalochordates ( Branchiostoma floridae ), echinoderms ( Strongylocentrotus purpuratus) and a mono-CRD galectin from the ascidian Clavelina picta . The Ci Lgals-a N-terminal and C-terminal CRDs contain the signature sequence involved in carbohydrate binding, whereas the Ci Lgals-b C-CRD presents only three out of seven key aminoacids and it could not be suitable as sugar binding motif. Sequence similarity between clusters suggests an evolutionary model based on CRD domain gene duplication and sequence diversification. In particular Ci Lgals-b N-CRD and C-CRD were similar to each other and both grouped with the ascidian C. picta mono-CRD. Homology modeling process shows a Ci Lgals molecular structure superimposed to chicken and mouse galectins. The Ci Lgals-a and Ci Lgals-b genes were upregulated by LPS inoculation suggesting that they are inducible and expressed in the inflamed pharynx as revealed by real-time PCR analysis. Finally, in situ hybridization and immunohistochemical assays showed their localization in the inflamed tissues, while immunoblotting analysis indicated that CiLgals can form oligomers.