Isolation and Expression of Two Aquaporin-Encoding Genes from the Marine Phanerogam Posidonia oceanica

Analysis of the repetitive component and retrotransposon population in the genome of a marine angiosperm, Posidonia oceanica (L.) Delile

Posidonia oceanica is a monocotyledonous marine plant that plays a crucial role in maintaining the Mediterranean environment. Despite its ecological importance, basic knowledge of the functional and structural genomics of this species is still limited, as it is for the other seagrasses. Here, for the first time, we report data on the repetitive component of the genome of this seagrass using a low coverage of Illumina sequences and different assembly approaches. A dataset of 19,760 assembled sequences, mostly belonging to the repetitive fraction of the genome, was produced and annotated. Based on mapping Illumina reads onto this dataset, the genome structure of P. oceanica and its repetitive component was inferred. A very large proportion of the genome is represented by long-terminal-repeat (LTR) retrotransposons of both the Copia and Gypsy superfamilies. Posidonia LTR-retrotransposons were classified and their sequences analysed. Gypsy elements belong to three main lineages, while Copia ones belong to seven lineages. Gypsy elements were more represented than Copia ones in the set of assembled sequences and in the genome. Analysis of sequence variability indicated that Gypsy lineages have experienced amplification in more recent times compared to Copia ones.

Highlights in Seagrasses’ Phylogeny, Physiology, and Metabolism: What Makes Them Special?

The marine seagrasses form an ecological and therefore paraphyletic group of marine hydrophilus angiosperms which evolved three to four times from land plants towards an aquatic and marine existence. Their taxonomy is not yet solved on the species level and below due to their reduced morphology. So far also molecular data did not completely solve the phylogenetic relationships. Thus, this group challenges a new definition for what a species is. Also their physiology is not well understood due to difficult experimental in situ and in vitro conditions. There remain several open questions concerning how seagrasses adapted secondarily to the marine environment. Here probably exciting adaptation solutions will be detected. Physiological adaptations seem to be more important than morphological ones. Seagrasses contain several compounds in their secondary metabolism in which they differ from terrestrial plants and also not known from other taxonomic groups. Some of these compounds might be of interest for commercial purposes. Therefore their metabolite contents constitute another treasure of the ocean. This paper gives an introduction into some of the most interesting aspects from phylogenetical, physiological, and metabolic points of view.

Role of aquaporins in leaf physiology

Playing a key role in plant growth and development, leaves need to be continuously supplied with water and carbon dioxide to fulfil their photosynthetic function. On its way through the leaf from the xylem to the stomata, water can either move through cell walls or pass from cell to cell to cross the different tissues. Although both pathways are probably used to some degree, evidence is accumulating that living cells contribute substantially to the overall leaf hydraulic conductance (K(leaf)). Transcellular water flow is facilitated and regulated by water channels in the membranes, named aquaporins (AQPs). This review addresses how AQP expression and activity effectively regulate the leaf water balance in normal conditions and modify the cell membrane water permeability in response to different environmental factors, such as irradiance, temperature, and water supply. The role of AQPs in leaf growth and movement, and in CO(2) transport is also discussed.