8.F.  Alternative Splicing Influencing Transport 

Interplays between cis- and trans-acting factors for alternative splicing in response to environmental changes during biological invasions of ascidians have been studied and described (Huang et al. 2023). Alternative splicing (AS), a pivotal biological process contributing to phenotypic plasticity, creates a bridge linking genotypes with phenotypes.  Using the model invasive congeneric ascidians, Ciona robusta, and Ciona savignyi, Huang et al. 2023 compared their AS responses to environmental changes and explored the potential determinants. Their findings unveiled swift and dynamic AS changes in response to environmental challenges, and differentially alternative spliced genes (DASGs) were functionally enriched in transmembrane transport processes. Both the prevalence and level of AS in C. robusta were lower than those observed in C. savignyi.  These two indices were higher under temperature stresses compared to salinity stresses in C. savignyi. All the observed patterns underscore the species-specific and environmental context- dependent AS responses to environmental challenges. The dissimilarities in genomic structure and exon/intron size distributions between these two species likely contributed to the observed AS variation. They identified a total of 11 and 9 serine/arginine-rich splicing factors (SRSFs) with conserved domains and gene structures in the genomes of C. robusta and C. savignyi, respectively. Their analysis revealed that all detected SRSFs did not exhibit prevalent AS regulations. Instead, they observed AS control over a set of genes related to splicing factors and spliceosome components. Thus, their results elucidated species-specific and environmental challenge-dependent AS response patterns in closely related invasive ascidians. The identified splicing factors and spliceosome components under AS control offer promising candidates for further investigations into AS-mediated rapid responses to environmental challenges complementary to SRSFs (Huang et al. 2023).