The littoral red alga Pyropia haitanensis uses rapid accumulation of floridoside as the desiccation acclimation strategy
Intertidal marine algae experience various abiotic stresses during low tide, such as desiccation. In this study, a red alga, Pyropia haitanensis, which is extremely tolerant to desiccation, was selected to investigate the physiological, chemical, and molecular responses of marine algae to desiccation. Osmoregulation and the synthesis of short-chain volatile compounds were studied in detail. The results showed that desiccation induced morphological and cellular changes, as well as a loss of about 98 % of the cell water. Desiccation markedly increased the content of osmoregulator floridoside in the alga. Two genes, PhNHO1, which encodes glycerokinase, and PhGPDH, which encodes glycerol-3-phosphate dehydrogenase, are involved in the biosynthesis of a floridoside precursor, glycerol-3-phosphate. Both genes were upregulated during desiccation. The species and content of short-chain volatiles changed considerably after the exposure to desiccation-inducing conditions. These changes included the production of 5-octen-1-ol, E,E-2,4-octadien-1-ol, 1-octanol, (6Z)-nonen-1-ol, and 2-nonenal, as well as the release of significant amounts of 3-octanone, dodecanoic acid, and 1-octen-3-ol. PhLOX1 and PhLOX2, which facilitate the initiation of production of downstream short-chain volatile compounds via the oxylipin pathway, were also upregulated. In summary, when exposed to desiccation conditions during low tide, stress-related responses were trigged in the alga. The concentration of floridoside, a solute involved in the osmoregulation and the expression of genes responsible for its synthesis, was increased to protect the cell from dehydration damage. Short-chain volatiles may act as pheromones and antibacterial agents.
KeywordsPyropia haitanensis Rhodophyta floridoside Desiccation Volatile organic compounds Gene expression Reactive oxygen species
This project was funded by NSFC project (81370532), National Spark Major Project (No. 2013GA701001), Ningbo Programs for Science and Technology Development (201201C1011016), Zhejiang Major Technology Project for Breeding of New Variety (2012C12907-6), K.C. Wong Magna Fund in Ningbo University; 151 Talents Project.
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