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. 2020 Apr 30;11:758. doi: 10.3389/fimmu.2020.00758

FIGURE 4.

FIGURE 4

Inferred evolutionary processes that may have led to the big defensin gene architecture observed in extant metazoan taxa. (A) mRNAs are indicated by green arrows and protein-coding regions are indicated with orange arrows. On the right-hand side, a schematic organization of the encoded precursor peptides is shown, including the signal peptide (SP), prodomain (PROD), N-terminal hydrophobic domain, linker and C-terminal β-defensin-like domain. Vertical black bars highlight the positioning of introns. (B) Multiple sequence alignment of the canonical (BigDefs) and non-canonical (ncBigDefs) big defensin peptides identified in the genomes and transcriptomes of Dreissena rostriformis and Ruditapes philippinarum. The organization of the main regions of the precursor peptides is shown at the bottom of the figure. The location of the phase I intron is indicated by a vertical bar (dashed in Dr-ncBigDefs, where it was lost). Note the large deletion of the N-terminal region which characterizes the non-canonical genes of both species.