Photoprotection enhanced by red cell wall pigments in three East Antarctic mosses

Abstract

BackgroundAntarctic bryophytes (mosses and liverworts) are resilient to physiologically extreme environmental conditions including elevated levels of ultraviolet (UV) radiation due to depletion of stratospheric ozone. Many Antarctic bryophytes synthesise UV-B-absorbing compounds (UVAC) that are localised in their cells and cell walls, a location that is rarely investigated for UVAC in plants. This study compares the concentrations and localisation of intracellular and cell wall UVAC in Antarctic Ceratodon purpureus, Bryum pseudotriquetrum and Schistidium antarctici from the Windmill Islands, East Antarctica.ResultsMultiple stresses, including desiccation and naturally high UV and visible light, seemed to enhance the incorporation of total UVAC including red pigments in the cell walls of all three Antarctic species analysed. The red growth form of C. purpureus had significantly higher levels of cell wall bound and lower intracellular UVAC concentrations than its nearby green form. Microscopic and spectroscopic analyses showed that the red colouration in this species was associated with the cell wall and that these red cell walls contained less pectin and phenolic esters than the green form. All three moss species showed a natural increase in cell wall UVAC content during the growing season and a decline in these compounds in new tissue grown under less stressful conditions in the laboratory.ConclusionsUVAC and red pigments are tightly bound to the cell wall and likely have a long-term protective role in Antarctic bryophytes. Although the identity of these red pigments remains unknown, our study demonstrates the importance of investigating cell wall UVAC in plants and contributes to our current understanding of UV-protective strategies employed by particular Antarctic bryophytes. Studies such as these provide clues to how these plants survive in such extreme habitats and are helpful in predicting future survival of the species studied.Electronic supplementary materialThe online version of this article (10.1186/s40659-018-0196-1) contains supplementary material, which is available to authorized users.

Semi-Automated Analysis of Digital Photographs for Monitoring East Antarctic Vegetation

“…Long-term monitoring coupled with image analysis improves our understanding of Antarctic vegetation health by underpinning a conceptual framework for how moss changes with stress and recovery (Figure 8). Antarctic moss health changes rapidly between stressed and healthy under ideal laboratory conditions, dependent on water availability, but further research is required to determine how long it takes for these changes under field conditions (Malenovský et al, 2015;Waterman et al, 2018). The color changes are caused by changes in the types of protective pigments (including anthocyanins and carotenoids) produced in the leaves of the moss (Post, 1990;Lovelock and Robinson, 2002;Waterman et al, 2018).…”

“…Antarctic moss health changes rapidly between stressed and healthy under ideal laboratory conditions, dependent on water availability, but further research is required to determine how long it takes for these changes under field conditions (Malenovský et al, 2015;Waterman et al, 2018). The color changes are caused by changes in the types of protective pigments (including anthocyanins and carotenoids) produced in the leaves of the moss (Post, 1990;Lovelock and Robinson, 2002;Waterman et al, 2018). ASPA mosses suffered stress resulting in pigment changes from green to red between 2003 and 2008, but this was reversed by subsequent loss of red pigments (red arrow) or growth of new leaves (green arrows).…”

The Evolution of Flavonoid Biosynthesis: A Bryophyte Perspective

“…Induction of auronidin in Marchantia by nitrogen and phosphorus also requires an R2R3MYB (Kubo et al, 2018), suggesting signaling components may be conserved. For Antarctic liverworts and mosses UVB exposure also induced production of red flavonoids, which most commonly were cell wall-bound (Newsham et al, 2005;Waterman et al, 2018). UVB induces anthocyanin production in some angiosperms, but it is much less common a response than induction of flavones/ flavonols.…”

Environmental effects of stratospheric ozone depletion, UV radiation, and interactions with climate change: UNEP Environmental Effects Assessment Panel, Update 2020

“…Despite their taxonomic differences, there are parallels in the adaptive responses of Antarctic bryophytes and vascular plants to UV-B radiation. Adaptive strategies to survive exposure to UV-B radiation in the moss, Pohlia nutans , include antioxidant enzymes, flavonoid synthesis and photolyases [ 137 – 139 ], whereas in Ceratodon purpureus various flavonoids confer photoprotection [ 140 ] along with yet to be identified red cell wall pigments [ 141 ]. The equivalent protection response of the vascular plant, Colobanthus quitensis , to UV radiation is enhanced by forming mutually beneficial relationships between plant roots and soil fungi (i.e., mycorrhizae).…”