Symbiodinium sp. cells produce light-induced intra- and extracellular singlet oxygen, which mediates photodamage of the photosynthetic apparatus and has the potential to interact with the animal host in coral symbiosis.
Coral bleaching is an important environmental phenomenon, whose mechanism has not yet been clarified. The involvement of reactive oxygen species (ROS) has been implicated, but direct evidence of what species are involved, their location and their mechanisms of production remains unknown. Histidine-mediated chemical trapping and singlet oxygen sensor green (SOSG) were used to detect intra- and extracellular singlet oxygen ((1) O2 ) in Symbiodinium cultures. Inhibition of the Calvin-Benson cycle by thermal stress or high light promotes intracellular (1) O2 formation. Histidine addition, which decreases the amount of intracellular (1) O2 , provides partial protection against photosystem II photoinactivation and chlorophyll (Chl) bleaching. (1) O2 production also occurs in cell-free medium of Symbiodinium cultures, an effect that is enhanced under heat and light stress and can be attributed to the excretion of (1) O2 -sensitizing metabolites from the cells. Confocal microscopy imaging using SOSG showed most extracellular (1) O2 around the cell surface, but it is also produced across the medium distant from the cells. We demonstrate, for the first time, both intra- and extracellular (1) O2 production in Symbiodinium cultures. Intracellular (1) O2 is associated with photosystem II photodamage and pigment bleaching, whereas extracellular (1) O2 has the potential to mediate the breakdown of symbiotic interaction between zooxanthellae and their animal host during coral bleaching.
Institute of Plant Biology, Biological Research Center of the Hungarian Academy of Sciences, PO Box 521, H-6701, Szeged, Hungary.
Ateeq Ur
AU
Rehman
Plant Functional Biology and Climate Change Cluster (C3), University of Technology Sydney, PO Box 123, Broadway, NSW, 2007, Australia.|Division of Plant Sciences, Research School of Biology, The Australian National University, 46 Sullivans Creek Road, Acton, ACT, 2601, Australia.
Milán
M
Szabó
Institute of Plant Biology, Biological Research Center of the Hungarian Academy of Sciences, PO Box 521, H-6701, Szeged, Hungary.
Zsuzsanna
Z
Deák
Institute of Plant Biology, Biological Research Center of the Hungarian Academy of Sciences, PO Box 521, H-6701, Szeged, Hungary.
László
L
Sass
Plant Functional Biology and Climate Change Cluster (C3), University of Technology Sydney, PO Box 123, Broadway, NSW, 2007, Australia.
Anthony
A
Larkum
Plant Functional Biology and Climate Change Cluster (C3), University of Technology Sydney, PO Box 123, Broadway, NSW, 2007, Australia.
Peter
P
Ralph
Institute of Plant Biology, Biological Research Center of the Hungarian Academy of Sciences, PO Box 521, H-6701, Szeged, Hungary. vass.imre@brc.mta.hu.
Imre
I
Vass
D000818:Animals; D037421:Anthozoa / Q000502:physiology*; D004141:Dinoflagellida / Q000166:cytology* / Q000187:drug effects / Q000528:radiation effects*; D005110:Extracellular Space / Q000737:chemistry; D005453:Fluorescence; D006639:Histidine / Q000494:pharmacology; D006358:Hot Temperature; D042541:Intracellular Space / Q000737:chemistry; D008027:Light; D010788:Photosynthesis / Q000187:drug effects / Q000528:radiation effects*; D045332:Photosystem II Protein Complex / Q000378:metabolism; D010860:Pigments, Biological / Q000378:metabolism; D026082:Singlet Oxygen / Q000378:metabolism*; D013559:Symbiosis / Q000187:drug effects / Q000528:radiation effects*
D045332:Photosystem II Protein Complex; D010860:Pigments, Biological; D026082:Singlet Oxygen; D006639:Histidine
Symbiodinium; algae; coral bleaching; photoinhibition; photosystem II (PSII); singlet oxygen (1O2)