Physiological and transcriptomic analysis reveal the response mechanisms to nutrient deficiencies in aquatic plant Spirodela polyrhiza.

Macrophytes are critical primary producers in freshwater ecosystems and offer potential as crop resources to support the growing human population. They are also widely used to mitigate eutrophication. Aquatic plants adapt themselves to the more complicated, changeable, and unstable conditions compared to terrestrial plants, especially the fluctuating nutrient environments. Nitrogen (N) and phosphorus (P) are the key nutrient elements for plants, and their biogeochemical cycles have been significantly disrupted by anthropogenic activities in diverse ecosystems. However, there is still a lack of comprehensive understanding about the adaptive mechanisms of N and P stress in aquatic plants. In this study, the response mechanisms in the macrophyte Spirodela polyrhiza under various nutrient conditions were analyzed. S. polyrhiza showed universal changes under nutrient deficiencies at the physiological level, including enhanced root growth, lower Chl content, higher Root-Frond ratio, and starch content. Genes involved in nutrient acquisition and remobilization, carbon metabolism, transcriptional regulation, hormones, and antioxidant systems were identified. Physiological and transcriptional changes revealed that the macrophyte S. polyrhiza adopts a nutrient acquisition-prioritization strategy under nutrient deficiency conditions, employing strategies similar to those observed in terrestrial plants. Post-transcriptional regulatory networks also highlighted the critical role of non-coding RNAs nutrient stress responses. Overall, S. polyrhiza employs integrated physiological and molecular strategies to cope with nutrient deficiency in aquatic environments. This study provides comprehensive insights into its adaptive responses and offers a valuable genetic resource for further novel gene discovery and functional analysis.