Potamogeton nodosus Assembly

450 MY ago, terrestrial plants emerged from aquatic environments1,2. This transition was made possible by evolutionary innovations that led to the development of specific traits such as cuticle, stomata, tracheids, and seeds, enabling them to adapt to life on land. More recently, some of these angiosperms have returned to an aquatic lifestyle by implementing new or already existing strategies3. This return was made possible, among other adaptations, by a remodeling of the extracellular matrix including the cell wall and the cuticle. The primary plant cell wall (CW) is composed of a polysaccharide portion (cellulose, hemicelluloses, and pectins) and a protein portion that gives it its dynamics.To investigate the mechanisms allowing this transition back to aquatic life, we have selected Potamogeton nodosus as one model species. This native plant of French rivers was collected in the Garonne River. It exhibits heterophylly, i.e. a morphological distinction between its floating and submerged leaves. After sequencing and assembling its genome, we conducted transcriptomic and cell wall proteomic studies. Additionally, microscopy was utilized to characterize the differences between the two types of leaves. The images acquired allow us to suspect the presence of lignin beneath the surface of floating leaves. Thanks to omics analyses, we were able to identify a differential accumulation of RNAs encoding enzymes involved in the lignin biosynthesis pathway. We will also discuss the distinct patterns of polysaccharide distribution, which may be related to the adaptive differences between submerged and floating leaves.