Increased susceptibility of algal symbionts to photo-inhibition resulting from the perturbation of coral gastrodermal membrane trafficking  

作　　者：CHEN Chii-Shiarng YEH Shih-Pin WANG Li-Hsueh LI Hsing-Hui CHEN Uang Wan-Nan 

机构地区：[1]Taiwan Coral Research Center,"National" Museum of Marine Biology & Aquarium,Pingtung 944,Taiwan,China [2]Institute of Marine Biotechnology,"National" Dong Hwa University,Pingtung 944,Taiwan,China [3]Department of Marine Biotechnology and Resources,"National" Sun Yat-Sen University,Kaohsiung 804,Taiwan,China [4]Department of Biological Science and Technology,I-Shou University,Kaohsiung 824,Taiwan,China

出　　处：《Science China(Life Sciences)》2012年第7期599-611,共13页中国科学（生命科学英文版）

基　　金：The present study is dedicated to the memory of our mentor Professor Richard E.Pagano (1944 2010);supported by the National Science Council of Taiwan (Grant No.NSC 98-2311-B-291-001-MY3).

摘　　要：The stability of cnidarian-dinoflagellate endosymbioses is dependent upon communication between the host gastrodermal cell and the symbionts housed within it. Although the molecular mechanisms remain to be elucidated, existing evidence suggests that the establishment of these endosymbioses may involve the sorting of membrane proteins. The present study examined the role of host gastrodermal membranes in regulating symbiont （genus Symbiodinium） photosynthesis in the stony coral Euphyllia glabrescens. In comparison with the photosynthetic behavior of Symbiodinium in culture, the Symbiodinium populations within isolated symbiotic gastrodermal cells （SGCs） exhibited a significant degree of photo-inhibition, as determined by a decrease in the photochemical efficiency of photosystem II （Fv/Fm）. This photo-inhibition coincided with increases in plasma membrane perturbation and oxidative activity in the SGCs. Membrane trafficking in SGCs was examined using the metabolism of a fluo- rescent lipid analog, N-[5-（5,7-dimethyl boron dipyrromethene difluoride）-l-pentanoyl]-D-erythro-Sphingosylpbosphoryl- choline （BODIPY-Sphingomyelin or BODIPY-SM）. Light irradiation altered both membrane distribution and trafficking of BODIPY-SM, resulting in metabolic changes. Cholesterol depletion of the SGC plasma membranes by methyl-13-cyclodextrin retarded BODIPY-SM degradation and further augmented Symbiodinium photo-inhibition. These results indicate that Symbio- dinium photo-inhibition may be related to perturbation of the host gastrodermal membrane, providing evidence for the pivotal role of host membrane trafficking in the regulation of this environmentally important coral-dinoflagellate endosymbiosis.The stability of cnidarian-dinoflagellate endosymbioses is dependent upon communication between the host gastrodermal cell and the symbionts housed within it.Although the molecular mechanisms remain to be elucidated,existing evidence suggests that the establishment of these endosymbioses may involve the sorting of membrane proteins.The present study examined the role of host gastrodermal membranes in regulating symbiont(genus Symbiodinium) photosynthesis in the stony coral Euphyllia glabrescens.In comparison with the photosynthetic behavior of Symbiodinium in culture,the Symbiodinium populations within isolated symbiotic gastrodermal cells(SGCs) exhibited a significant degree of photo-inhibition,as determined by a decrease in the photochemical efficiency of photosystem II(F v /F m).This photo-inhibition coincided with increases in plasma membrane perturbation and oxidative activity in the SGCs.Membrane trafficking in SGCs was examined using the metabolism of a fluorescent lipid analog,N-[5-(5,7-dimethyl boron dipyrromethene difluoride)-1-pentanoyl]-D-erythro-Sphingosylphosphorylcholine(BODIPY-Sphingomyelin or BODIPY-SM).Light irradiation altered both membrane distribution and trafficking of BODIPY-SM,resulting in metabolic changes.Cholesterol depletion of the SGC plasma membranes by methyl--cyclodextrin retarded BODIPY-SM degradation and further augmented Symbiodinium photo-inhibition.These results indicate that Symbiodinium photo-inhibition may be related to perturbation of the host gastrodermal membrane,providing evidence for the pivotal role of host membrane trafficking in the regulation of this environmentally important coral-dinoflagellate endosymbiosis.

关 键 词：CNIDARIA ENDOSYMBIOSIS fluorescent lipids lipid trafficking PAM photosynthesis SYMBIODINIUM 

分 类 号：X173[环境科学与工程—环境科学]