Alternative splicing is coordinated through interconnected response pathways to direct major features of fungal cell physiology

Alternative splicing (AS) is a fundamental post-transcriptional process that expands transcriptomic and proteomic diversity by generating multiple mRNA isoforms from a single gene. In fungi, AS not only contributes to proteome complexity but also appears to influence key biological processes, including development, morphogenesis, pathogenicity, stress responses, and environmental adaptation. Unlike animals and plants, in which exon skipping predominates, intron retention is the most prevalent AS mode in fungal species, suggesting unique evolutionary pressures and regulatory strategies. The spliceosome, along with splicing factors such as serine/arginine-rich proteins and heterogeneous nuclear ribonucleoproteins, orchestrates the precise selection of splice-sites. However, the mechanisms linking AS to cellular signaling and environmental cues remain largely unresolved. This review summarizes recent advances in our understanding of fungal AS and highlights its regulatory potential, adaptive significance, and evolutionary implications. Here, we discuss how stimulus-dependent splicing operates as a controlled response mechanism and provide a comprehensive perspective on the functional dimension of splicing in fungi. We propose that a landscape of splicing signal conservation/degeneration has been shaped in fungal genomes throughout evolution, which determines the intrinsic propensity for regulated AS events at individual splice sites.