TY - JOUR
T1 - Photosystem II recovery in the presence and absence of chloroplast protein repair in the symbionts of corals exposed to bleaching conditions
AU - Hill, R.
AU - Takahashi, S.
N1 - Publisher Copyright:
© 2014, Springer-Verlag Berlin Heidelberg.
PY - 2014/12
Y1 - 2014/12
N2 - Increased seawater temperature causes photoinhibition due to accumulation of photodamaged photosystem II (PSII) in symbiotic algae (genus Symbiodinium) within corals, and it is assumed to be associated with coral bleaching. To avoid photoinhibition, photosynthetic organisms repair the photodamaged PSII through replacing the PSII proteins, primarily the D1 protein, with newly synthesised proteins. However, in experiments using cultured Symbiodinium strains, the PSII repair of Symbiodinium has been suggested not to be related to the synthesis of the D1 protein. In this study, we examined the relationship between the recovery of PSII photochemical efficiency (FV/FM) and the content of D1 protein after high-light and high-temperature treatments using the bleaching-sensitive coral species, Pocillopora damicornis and Acropora millepora, and the bleaching-tolerant coral species, Montipora digitata and Pavona decussata. When corals were exposed to strong light (600 µmol photons m−2 s−1) at elevated temperature (32 °C) for 8 h, significant bleaching occurred in bleaching-sensitive coral species although an almost similar extent of reduced PSII function was found across all coral species tested. During a subsequent 15-h recovery under low light (10 µmol photons m−2 s−1) at optimal temperature (22 °C), the reduced FV/FM recovered close to initial levels in all coral species, but the reduced D1 content recovered only in one coral species (Pavona decussata). D1 content was therefore not strongly linked to chloroplast protein synthesis-dependent PSII repair. These results demonstrate that the recovery of photodamaged PSII does not always correspond with the recovery of D1 protein content in Symbiodinium within corals, suggesting that photodamaged PSII can be repaired by a unique mechanism in Symbiodinium within corals.
AB - Increased seawater temperature causes photoinhibition due to accumulation of photodamaged photosystem II (PSII) in symbiotic algae (genus Symbiodinium) within corals, and it is assumed to be associated with coral bleaching. To avoid photoinhibition, photosynthetic organisms repair the photodamaged PSII through replacing the PSII proteins, primarily the D1 protein, with newly synthesised proteins. However, in experiments using cultured Symbiodinium strains, the PSII repair of Symbiodinium has been suggested not to be related to the synthesis of the D1 protein. In this study, we examined the relationship between the recovery of PSII photochemical efficiency (FV/FM) and the content of D1 protein after high-light and high-temperature treatments using the bleaching-sensitive coral species, Pocillopora damicornis and Acropora millepora, and the bleaching-tolerant coral species, Montipora digitata and Pavona decussata. When corals were exposed to strong light (600 µmol photons m−2 s−1) at elevated temperature (32 °C) for 8 h, significant bleaching occurred in bleaching-sensitive coral species although an almost similar extent of reduced PSII function was found across all coral species tested. During a subsequent 15-h recovery under low light (10 µmol photons m−2 s−1) at optimal temperature (22 °C), the reduced FV/FM recovered close to initial levels in all coral species, but the reduced D1 content recovered only in one coral species (Pavona decussata). D1 content was therefore not strongly linked to chloroplast protein synthesis-dependent PSII repair. These results demonstrate that the recovery of photodamaged PSII does not always correspond with the recovery of D1 protein content in Symbiodinium within corals, suggesting that photodamaged PSII can be repaired by a unique mechanism in Symbiodinium within corals.
KW - Coral bleaching
KW - D1 protein
KW - Heat stress
KW - Photoinhibition
KW - Protein repair
KW - Symbiodinium
UR - http://www.scopus.com/inward/record.url?scp=84940277494&partnerID=8YFLogxK
U2 - 10.1007/s00338-014-1188-4
DO - 10.1007/s00338-014-1188-4
M3 - Article
SN - 0722-4028
VL - 33
SP - 1101
EP - 1111
JO - Coral Reefs
JF - Coral Reefs
IS - 4
ER -