Transposable elements in a myxozoan–fish system: their role in the lateral transfer of host Siglec genes

Mobile DNA sequences, known as transposable elements (TEs), are potent drivers of genomic evolution, capable of altering genome structure and modulating gene expression by acting as promoters, enhancers, and other regulatory elements. This study investigates the role of TEs in facilitating lateral gene transfer (LGT) within the intimate host-parasite system of the myxozoan Ceratonova shasta and its host, rainbow trout ( Oncorhynchus mykiss ). Our findings indicate that TEs in C. shasta have mediated the LGT of host-derived genes. Through genomic and transcriptomic analyses, our results pointed out a DNA transposon, DNA/hAT-Charlie , as the primary vector responsible for transferring specific silica-dependent immune-related genes from the host to the parasite. Transcriptome analysis revealed a coordinated transcriptional response during infection, with significant expression of transposon-related genes in both the C. shasta and infected host, contrasting with minimal expression in uninfected hosts. This evidence refutes simple sample contamination and points toward a dynamic molecular interplay. These results underscore the profound regulatory potential and mobility of TEs in driving host-parasite coevolution and rapid genomic adaptation.