FIGURE 6.

Tandem duplication and positive selection of TLRs in C. virginica. (A), Tandem repeats as the major source of TLRs duplication in C. virginica. (B), The largest tandem repeat cluster (Top) and divergent expression patterns (Bottom) of tandemly linked TLRs in NC_035786.1 under P. marinus challenge. The wide arrows represent TLR genes, and genes with red background are differentially expressed under P. marinus challenge. A pseudogene LOC111105057 was detected in this repeat cluster. (C), Evolutionary relationships of duplicated TLRs. The calculated d_N/d_S (ω) values (gold) and bootstrap values are shown for each branch. The branches with ω values >1.0 are marked with red rectangle. The differential genes under P. marinus challenge that are positively selected are boxed with red dash lines. (D), Structural modeling of TLR depicting sites (blue) under positive selection. Positive selection sites (Asp²⁷, Glu⁶², Asn¹⁹⁹) are represented by black arrows.