Fig. 2

Phylogenetic relationships and domain architectures of the 122 chitinases (Chis) from Thalassiosira oceanica (To), Thalassiosira pseudonana (Tp), and Thalassiosira weissflogii (Tw). The T. pseudonana chitinases are indicated using the symbol “O”. Inner layer: An unrooted phylogenetic tree constructed with MEGA using the NJ (neighbor-joining) method and 1000 bootstrap replicates. The eight groups (I–VII) are distinguished by colours, and the four unclassified chitinases are shown in a light blue shade. Outer layer: Distribution of the chitinase protein domains, denoted by boxes of different colours and shapes. The glyco_hydro_19 domains are represented by blue oval boxes, and the glyco_hydro_18 domains are represented by green oval boxes; their positions can be inferred by the circular scales around the tree