TY - JOUR
T1 - Towards clarifying what distinguishes cyanobacteria able to resurrect after desiccation from those that cannot
T2 - The photosynthetic aspect
AU - Raanan, Hagai
AU - Oren, Nadav
AU - Treves, Haim
AU - Keren, Nir
AU - Ohad, Itzhak
AU - Berkowicz, Simon M.
AU - Hagemann, Martin
AU - Koch, Moriz
AU - Shotland, Yoram
AU - Kaplan, Aaron
N1 - Publisher Copyright:
© 2016 Elsevier B.V. All rights reserved.
PY - 2016/6
Y1 - 2016/6
N2 - Organisms inhabiting biological soil crusts (BSCs) are able to cope with extreme environmental conditions including daily hydration/dehydration cycles, high irradiance and extreme temperatures. The photosynthetic machinery, potentially the main source of damaging reactive oxygen species during cessation of CO2 fixation in desiccating cells, must be protected to avoid sustained photodamage. We compared certain photosynthetic parameters and the response to excess light of BCS-inhabiting, desiccation-tolerant cyanobacteria Leptolyngbya ohadii and Nostoc reinholdii with those observed in the "model" organisms Nostoc sp. PCC 7120, able to resurrect after mild desiccation, and Synechococcus elongatus PCC 7942 and Synechocystis sp. PCC 6803 that are unable to recover from dehydration. Desiccation-tolerant strains exhibited a transient decline in the photosynthetic rate at light intensities corresponding to the inflection point in the PI curve relating the O2 evolution rate to light intensity. They also exhibited a faster and larger loss of variable fluorescence and profoundly faster QA- re-oxidation rates after exposure to high illumination. Finally, a smaller difference was found in the temperature of maximal thermoluminescence signal in the absence or presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) than observed in "model" cyanobacteria. These parameters indicate specific functional differences of photosystem II (PSII) between desiccation tolerant and sensitive cyanobacteria. We propose that exposure to excess irradiation activates a non-radiative electron recombination route inside PSII that minimizes formation of damaging singlet oxygen in the desiccation-tolerant cyanobacteria and thereby reduces photodamage.
AB - Organisms inhabiting biological soil crusts (BSCs) are able to cope with extreme environmental conditions including daily hydration/dehydration cycles, high irradiance and extreme temperatures. The photosynthetic machinery, potentially the main source of damaging reactive oxygen species during cessation of CO2 fixation in desiccating cells, must be protected to avoid sustained photodamage. We compared certain photosynthetic parameters and the response to excess light of BCS-inhabiting, desiccation-tolerant cyanobacteria Leptolyngbya ohadii and Nostoc reinholdii with those observed in the "model" organisms Nostoc sp. PCC 7120, able to resurrect after mild desiccation, and Synechococcus elongatus PCC 7942 and Synechocystis sp. PCC 6803 that are unable to recover from dehydration. Desiccation-tolerant strains exhibited a transient decline in the photosynthetic rate at light intensities corresponding to the inflection point in the PI curve relating the O2 evolution rate to light intensity. They also exhibited a faster and larger loss of variable fluorescence and profoundly faster QA- re-oxidation rates after exposure to high illumination. Finally, a smaller difference was found in the temperature of maximal thermoluminescence signal in the absence or presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) than observed in "model" cyanobacteria. These parameters indicate specific functional differences of photosystem II (PSII) between desiccation tolerant and sensitive cyanobacteria. We propose that exposure to excess irradiation activates a non-radiative electron recombination route inside PSII that minimizes formation of damaging singlet oxygen in the desiccation-tolerant cyanobacteria and thereby reduces photodamage.
KW - Dehydration
KW - Drought stress
KW - Fluorescence
KW - Photosynthetic activity
KW - Photosystem II
KW - Q-reoxidation
UR - http://www.scopus.com/inward/record.url?scp=84964682594&partnerID=8YFLogxK
U2 - 10.1016/j.bbabio.2016.02.007
DO - 10.1016/j.bbabio.2016.02.007
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C2 - 26896589
AN - SCOPUS:84964682594
SN - 0005-2728
VL - 1857
SP - 715
EP - 722
JO - Biochimica et Biophysica Acta - Bioenergetics
JF - Biochimica et Biophysica Acta - Bioenergetics
IS - 6
ER -