Effect of UV-B Radiation and Desiccation Stress on Photoprotective Compounds Accumulation in Marine Leptolyngbya sp.

Increased awareness regarding the harmful effects of ultraviolet (UV)-B radiation
has led to the search for new sources of natural UV-B protecting compounds. Mycosporinelike
amino acids are one of such promising compounds found in several organisms.
Cyanobacteria are ideal organisms for isolation of these compounds due to their compatibility
and adaptability to thrive under harsh environmental conditions. In the following investigation,
we report the production of shinorine in Leptolyngbya sp. isolated from the intertidal region.
Based on the spectral characteristics and liquid chromatography-mass spectrometry analysis,
the UV-absorbing compound was identified as shinorine. To the best of our knowledge, this is
the first report on the occurrence of shinorine in Leptolyngbya sp. We also investigated the
effect of artificial UV-B radiation and periodic desiccation on chlorophyll-a, total carotenoids,
and mycosporine-like amino acids (MAAs) production. The UV-B radiation had a negative
effect on growth and chlorophyll concentration, whereas it showed an inductive effect on the
production of total carotenoids and MAAs. Desiccation along with UV-B radiation led to an
increase in the concentration of photoprotective compounds. These results indicate that
carotenoids and MAAs thus facilitate cyanobacteria to avoid and protect themselves from
the deleterious effects of UV-B and desiccation.