In a recent project, we have begun to analyze the occurrence and evolution of mycosporine-like amino acids (MAAs) in algae. This work was triggered by our participation in the genome annotation of the red alga Porphyra umbilicalis that accumulates MAAs up to 1% of its dry weight. MAAs are UV-absorbing pigments found in a wide range of organisms such as bacteria, fungi, algae and even animals. Among algae, MAAs have been found mainly in red and green algal species that are frequently exposed to elevated UV radiation, indicating their involvement in protecting the photosynthetic apparatus against UV-induced damage.
Comparative genomics indicate that the MAA biosynthetic genes are organized in clusters not only in bacteria but also in algae and other eukaryotic organisms. Such an organization facilitates a transmission of the MAA biosynthetic pathway between unrelated species by horizontal gene transfer and could principally explain the strikingly patchy occurrence of MAA biosynthesis among algae. Our phylogenetic analyses, however, favor the alternative scenario that algae acquired the MAA biosynthetic genes only once by the cyanobacterial endosymbiont that gave rise to their plastids, followed by a subsequent loss of MAA biosynthesis in the majority of extant algal species. To better understand the evolution of algal MAAs, we currently are aiming at the functional characterization of MAA biosynthetic genes from various algae.
Brawley et al. (2017), Lohr (2017)