Gene expression remodeling, poly(A) tail regulation and alternative splicing define transcriptomic responses to microplastic exposure in the liverwort Riccia fluitans

Although micro- and nanoplastics (MNPs) are new environmental pollutants that are becoming more and more important for plant biology, little is known about how they affect early-diverging terrestrial plants molecularly. Using nanopore sequencing, we investigated the transcriptome responses of the liverwort Riccia fluitans to different concentrations of PET-derived MNPs. Exposure to the high dose triggered extensive transcriptome reprogramming, as reflected by pronounced differential gene expression, widespread poly(A) tail shortening, and alternative splicing changes. Genes associated with photosynthesis were mostly downregulated with shortened poly(A) tails, indicating disturbed translational control and mRNA stability. Stress pathways were strongly induced, especially in response to oxidative and abiotic stress. Alternative splicing analyses identified significant isoform switching in defense-related genes such as CAL3 and PAPR independent of overall expression changes. Our findings suggest that nanoplastics are strong abiotic stressors eliciting coordinated transcriptional and post-transcriptional regulation in R. fluitans . This study emphasizes conserved regulatory pathways across terrestrial plants and offers the first comprehensive long-read transcriptome analysis of MNP-induced stress responses in liverworts.