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

Paul A Keller,Melinda J Waterman,Sharon A Robinson,Jessica Bramley-Alves,Rebecca E Miller

doi:10.1186/s40659-018-0196-1

Paul A Keller, Melinda J Waterman + Show 3 more

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https://doi.org/10.1186/s40659-018-0196-1

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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.

Highlights

Antarctic bryophytes are resilient to physiologically extreme environmen‐ tal conditions including elevated levels of ultraviolet (UV) radiation due to depletion of stratospheric ozone
It was shown that Antarctic C. purpureus, B. pseudotriquetrum and S. antarctici have reduced cell wall UVB-absorbing compounds when grown in favourable conditions such as low light
Higher concentrations of cell wall UV-B-absorbing compounds were observed in red compared to green growth forms of Antarctic C. purpureus collected from the field

Summary

Introduction

Antarctic bryophytes (mosses and liverworts) are resilient to physiologically extreme environmen‐ tal conditions including elevated levels of ultraviolet (UV) radiation due to depletion of stratospheric ozone. This study compares the concentrations and localisation of intra‐ cellular and cell wall UVAC in Antarctic Ceratodon purpureus, Bryum pseudotriquetrum and Schistidium antarctici from the Windmill Islands, East Antarctica. Undulating moss turfs are common in coastal Antarctica, especially in the Windmill Islands region where moss landscapes of small peaks and valleys are found (Additional file 1: Figure S1). This microtopography causes microclimatic differences in temperatures and water availability as well as exposure to wind and radiation; all of which drive species health and distributions in the bryophyte community. The differences in specific compounds between red and green varieties have not been investigated for these Antarctic bryophytes

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