Transcriptomic regulation of aquaporins during seed germination in the marine seagrass Cymodocea nodosa

Abstract

Seed germination is a key phase that transitions the seed from dormancy to active growth, where imbibition emerges as the initial event, followed by aquaporin-mediated regulation of cellular water that supports metabolic reactivation under favourable conditions. Aquaporins are small integral membrane proteins that facilitate the passive transport of water and small solutes across membranes and play key roles in plant development and physiology. In terrestrial plants, aquaporins are classified into five main types-PIPs, TIPs, NIPs, SIPs, and XIPs-with PIPs and TIPs being the most abundant and widely expressed. Whilst knowledge of seagrass aquaporins and their physiological roles remains limited, their functional involvement in seed germination is largely unknown. In this study of the marine seagrass Cymodocea nodosa, transcriptome assembly and analysis enabled the identification of aquaporin-encoding sequences, which were subsequently used for gene expression analysis during germination. Three well-defined seed stages of C. nodosa were analysed to assess expressions patterns of PIPs, TIPs, NIPs, and SIPs. Results showed that transcript levels of PIP, TIP, and SIP aquaporins exhibit differential expression patterns, and the changes are mainly associated with activation responses related to seed germination progress. Overall, this study provides one of the first foundations for investigating aquaporin function during seed germination in marine seagrasses, defining expression patterns across imbibition and early germination, and positioning C. nodosa as a valuable in vitro model for exploring the regulation of aquaporin activity by environmental and physiological factors.