A new mechanistic understanding of light-limitation in the seagrass Zostera muelleri

In this study we investigated the effect of light limitation (~20 µmol photons m-2 s-1) on the southern hemisphere seagrass, Zostera muelleri. RNA sequencing, chlorophyll fluorometry and HPLC techniques were used to investigate how the leaf-specific transcriptome drives changes in photosynthesis and photo-pigments in Z. muelleri over 6 days. 1,593 (7.51%) genes were differentially expressed on day 2 and 1,481 (6.98%) genes were differentially expressed on day 6 of the experiment. Differential gene expression correlated with significant decreases in rETRMax, Ik, an increase in Yi (initial photosynthetic yield of photosystem II), and with significant changes in pigment regulation and composition. Regulation of carbohydrate metabolism was observed along with evidence that abscisic acid may serve a role in the low-light response of this seagrass. This study provides a novel understanding of how Z. muelleri responds to light limitation in the marine water column and provides potential molecular markers for future monitoring conservation efforts.