수환경 내 식물플랑크톤에 의해 생성된 광보호 물질에 대한 연구

Abstract

1) Porosira glacialis의 mycosporine-like amino acids 및 색소의 실시간적인 광보호 반응 연구 본 연구는 13C 추적자를 이용하여 실시간으로 생성되는 Porosira glacialis의 광보호 물질에 대하여 연구하였다. 본 연구 결과 P. glacialis은 자외선에 노출됨에도 불구하고 성장율과 엽록소 a 농도를 통하여 자외선에 대한 저항력을 가지고 있음을 확인하였다. 광합성 유효광에 24시간동안 끊임없이 노출된 경우의 탄소 흡수 능력은 자외선에 노출된 P. glacialis보다 높은 흡수율을 보이고 있다. 하지만, 72시간동안 노출된 경우 자외선에 노출된 P. glacialis의 탄소흡수능력은 오히려 광합성유효광에 비해 높은 결과를 보이다. 광보호 물질인 (Mycosporien like amino acids and Diadinoxanthin)의 생성은 서로 다른 시간에 생성함으로서 P. glacialis의 광보호 전략을 볼 수 있다. 본 연구를 통하여, 광보호 물질의 생성 경로가 서로 다름을 확인하였고, 세포 내 탄소 순환이 광보호 색소 및 MAAs의 생산력을 통하여 서로 다른 양상을 가짐을 확인하였다.

2) 북극 스발바드 Konsfjorden의 현장 식물플랑크톤의 Mycosporine-like amino acids의 생산력 연구 본 연구는 북극 스발다드 kongsfjorden 만 외해와 내해의 식물플랑크톤 군집구조에 따른 자외선 흡수 물질의 공간적인 분포에 대해 조사하였다. Kongsfjorden 외해은 Phaeocystis sp. 와 Thalassiosira sp. 가 우점하면서 높은 chl.a 농도를 보임에도 불구하고 낮은 MAAs 농도를 보이고 있다. 하지만 Kongsfjorden 내만은 Phaeocystis sp. 가 우점하면서 낮은 chl a 농도를 보임에도 불구하고 높은 MAAs 농도를 보이고 있다. Kongsfjorden 만 안쪽에 위치한 정점 (T05)에서의 탄소 고정 능력이 자외선에 의해서 상당히 억제됨에도 불구하고, 만 외해 쪽 정점 (B09)에 비해 높은 MAAs 생산력 및 단위 chl a 당 MAAs 생산력이 높다. 또한 각 MAAs의 탄소순환 속도 또한 Kongsfjorden 만 안쪽이 외해보다 빠른 결과를 보이고 있다. 본 연구 결과를 통하여, 자연상태의 식물플랑크톤 군집은 식물플랑크톤 종조성 (Thalassiosira sp. vs. Phaeocystis sp.) 에 따라 서로 다른 자외선 적응 메커니즘을 가지고 있다. 본 연구를 통하여, 자연 상태 식물플랑크톤 군집의 새롭게 생성된 자외선 흡수 물질인 MAAs의 실시간으로 변화하는 양상을 확인하였다. 탄소 안정동위원소 추적자 및 고성능 액체 크로마토그래피에 결합된 동위원소 질량분석기를 이용하여 현장의 MAAs 생산력을 추정하였다.

3) 북극 스발바드 Konsfjorden의 식물플랑크톤 군집의 Mycosporine-like amino acids, DMSP 그리고 광보호 색소의 관계 연구 본 연구는 2009년 봄철 Kognsfjorden 주변 해역의 자외선 흡수 물질인 mycosporine like amino acids (MAAs)와 광보호 색소인 Diadinoxanthin(DD) 과 Diatoxanthin(DT), 그리고 β-dimethylsulphoniumpropionate (DMSP)의 광보호 역할에 대한 상호 관계를 알아보고자 했다. 아북극권인 스발바드 섬 서쪽 Kongsfjorden 의 만안쪽 및 외해 그리고 서스피츠베르겐 해류의 영향을 받은 해역의 표층 해수를 채수하였다. Fucoxanthin to chlorophyll ratios (Fuco/chl.a ratios)가 상대적으로 다른 해역에 비해 높은 값을 보임으로서, 규조류의 영향이 다른 해역에 비해 높은 것을 볼 수 있다. 해류 (WSC)의 영향를 받는 해역은 상대적으로 높은 군집 구조에 따라 서로 다른 생존 전략을 가지고 있는 것으로 보인다. Chlorophyll-specific concentrations of UV-absorbing mycosporine-like amino acids와 DD+DT to chlorophyll ratios ((DD+DT)/chl.a ratios)은 Kongsfjorden 내만에서 상대적으로 높은 경향을 두 물질간 보여주고 있으며 상호 보완적인 관계를 가지고 있는 것으로 보인다. 그러나 DMSP/chl.a ratios의 경우, 환경적인 요인의 영향과 종간 특이성으로 인하여 뚜렷한 공간적인 분포를 보여주진 않는다. 본 연구를 통하여 식물플랑크톤의 광보호 전략에 있어 종의 특이성에 따라 선택적인 전략을 추구하지만 자연 환경에서는 특히 자외선 흡수 물질과 광보호 색소간 상호 보완적인 관계가 뚜렷하게 나타나는 것을 확인할 수 있다.

4) 중위도 호수의 식물플랑크톤 종조성에 따른 Mycosporine-like amino acids 생산력의 계절적 변화 연구 탄소 안정동위원소를 이용하여 현장 배양된 식물플랑크톤을 자연 자외선에 노출 후 자외선의 효과에 의한 광보호 물질인 Mycosporine like amino acids (MAAs)의 단위 시간당 생산력을 계산하였다. 중위도에 위치한 한반도의 자외선 강도는 7월과 8월에 가장 센 시기로 관측되었다. 팔당호와 청평호 두 호수의 식물플랑크톤 군집은 모든 달에서 규조류가 다른 식물플랑크톤에 비해 우점하고 있는 특징을 가지고 있으며, 청평호의 경우 7월에 남조류가 80% 이상의 상대적인 현존량을 보이는 현상을 보였다. MAAs의 농도는 팔당호의 경우 10월에 가장 높은 값을 보이고 있으며, 청평호는 9월에 가장 높은 MAAs 농도값을 보이며, 이는 식물플랑크톤 군집 구조의 변화에 따라 계절별로 다른 값을 보이고 있다. 또한 팔당호의 현장배양 실험을 통한 MAAs의 생산력은 10월 가장 높은 값을 보이고 있다. 모든 달에서 규조류가 극우점하면서 자외선에 대한 규조류의 long-term response를 보이고 있는 것으로 사료된다. 청평호의 MAAs 생산력 변화는 자외선의 강도가 가장 높았던 7월에 가장 뚜렷한 증가를 보이고 있으며, 자외선에 대해 민감하게 반응하는 남조류의 우점으로 인하여 직접적인 반응을 보이고 있다. 결과적으로 MAAs 생성과 자외선 흡수 물질에 대한 광유도 현상은 식물플랑크톤 군집 구조에 따라 차이를 보이며, 또한 계절별 자외선은 식물플랑크톤 군집 구조에 (특히 cyanopyceae) MAAs 생산력 및 농도 변화에 영향을 주고 있다.

식물플랑크톤은 유해한 자외선에 노출시 스스로 보호하기 위해서 끊임없이 자외선 흡수 물질 및 광보호 물질을 생성하고 있으며, 자외선 흡수 물질과 광보호 물질간 생성 시간 차이로 인하여 보다 효과적인 광보호 전략을 가지고 있다. 본 연구는 자외선 흡수 물질과 광보호 물질을 탄소 안정동위원소 추적자를 이용하여 분자 수준의 물질 분석(compound-specific stable isotope analysis)을 활용하였다. |1) Real-time photoprotective response of xanthophyll pigments and mycosporine-like amino acids of Porosira glacialis (Bacillariophycease) This study is an investigation of the newly synthesis of photoprotective compounds by Porosira glacialis in real time using a 13C tracer. Our results show that UV tolerance of P. glacialis was evidenced by the growth rate and chlorophyll a (Chl a) concentration under the UV conditions. The carbon uptake rate indicated that was continuously exposed to photosynthetically active radiation (PAR) for 24 hours, which was higher than that of one exposed to ultraviolet (UV) radiation (UVR). However, it indicated when the exposure time was 72 hours, which was higher than the initial value of P. glacialis exposed to UV radiation and also was higher than that of P. glacialis exposed to PAR. The time difference between the productions of these two compounds clearly reveals the defense strategy used by P. glacialis to synthesize photoprotective compounds (MAAs and DD). The results of this study appear to reflect the synthetic pathways of photoprotective compounds and the carbon cycle within the cell in contrasting patterns over time that are defined by the production of photoprotective pigments (DD) and MAAs.

2) Production of Mycosporine-like amino acids of in situ phytoplankton community in Kongsfjorden, Svalbard, Arctic The spatial distribution of UV-absorbing compounds (Mycosporine-like amino acids, MAAs), was investigated by comparing the phytoplankton community structures in the inner and outer waters of the Kongsfjorden inlet, which is located in arctic Svalbard. Thalassiosira sp. and Phaeocystis sp. were dominant in the outer waters of the Kongfjorden inlet, demonstrating high chlorophyll a (chl a) concentrations and low MAA concentrations in the outer bay waters. However, Kongsfjorden Bay was dominated by Phaeocystis sp. and demonstrated high MAA concentrations despite low chl a concentrations. The carbon fixation rate at a station located inside Kongsfjorden Bay (T05) was significantly photo-inhibited by UV radiation, demonstrating higher production rates of MAA and chl a than at a station (B09) in outer bloom waters. Additionally, the turnover rates of individual MAAs were faster inside the Kongsfjorden Bay than in the outside waters. As a result, the natural phytoplankton community demonstrated different UV adaptation mechanisms according to the phytoplankton species, in this case, Thalassiosira sp. vs. Phaeocystis sp. It is possible to understand real-time changes for newly photosynthesized MAAs as UV-absorbing compounds in the natural phytoplankton community. This takes place via determination of in situ MAA production rates using 13C tracer and High Performance Liquid Chromatography (HPLC) combined with an isotope ratio mass spectrometer (irMS).

3) Relationship of Mycosporine-like amino acids, DMSP and photo-protective pigment of phytoplankton assemblage in Kongsfjorden, Svalbard, Arctic We investigated ultraviolet radiation (UV)-absorbing compounds (mycosproine-like amino acids (MAAs)), photoprotective xanthophylls compounds (diadinoxanthin (DD), diatoxanthin (DT)) and dimethylsulphoniumpropionate (DMSP) for their photoprotective function of phytoplankton. in Kongsfjorden, Svalbard, Arctic springtime. Surface water was collected from the inner bay and offshore of Kongsfjorden on the western side of Svalbard Island in the Subarctic Circle and from waters influenced by the West Spitsbergen Current (WSC). The fucoxanthin to chlorophyll (fuco-chl) ratio was commonly higher in a chlorophyll maximum area (offshore sea), wherefore more diatoms inhabit there. Chl a concentration showed a comparatively higher level in WSC waters. On the other hand, the inner bay which has been relatively low chl a concentration showed a relatively lower fuco-chl ratio and was dominated by phytoplankton, like Phaeocystis sp. and nanoflagellate. Phytoplankton assemblage have been influenced WSC and distinguished dominated phytoplankton species according to region that inner bay represented dominated Phaeocystis sp. and Thalassiosira sp. at offshore. So, our results indicated the relatively different of strategy through the phytoplankton assemblage. UV-absorbing compounds (MAAs) exhibits higher in chlorophyll-specific concentration and the ratio of DD and DT to chlorophyll (DD/DT-chl ratio) tends to be higher in the inner bay. Thus, they seemed to be complementary to each other. However, the ratio of β-DMSP to chlorophyll (DMSP-chl ratio) does not show a distinct spatial distribution due to environmental factors and interspecies specificities. In this study, it was found that photoprotective strategies selectively as to species specificity, but that UV-absorbing compounds and photoprotective pigments are distinctly complementary to each other under natural environments.

4) Seasonal changes in production rates of Mycosporine-like amino acids in relation to phytoplankton species composition in mid-latitude temperate lakes The production rate of mycosporine-like amino acids (MAAs) was calculated using carbon stable isotopes on phytoplankton that was exposed to UV radiation after in situ incubation at the site for one year (every month). In the middle latitudes of the Korean Peninsula, UV radiation reached peak intensity between July and August. In Lake Paldang and Lake Cheongpyeong, diatoms were the dominant species of phytoplankton throughout the year. In Lake Cheongpyeong, the relative abundance of cyanophyceae (Anabaena spiroides) reached over 80% in July. Changes in phytoplankton abundance implies that the phytoplankton community structure is influenced by seasonal changes in the production rate and concentration of MAAs. POM cultured in Lake Paldang secreted the most MAAs during October. The dominance of diatoms in phytoplankton composition suggests that they have a long-term response to UV radiation. POM cultured in Lake Cheongpyeong showed the greatest increase in the production of MAAs in July when UV radiation reached its peak intensity. POM had an immediate response to UV radiation due to the dominance of cyanobacteria that are hypersensitive to UV radiation. The results showed that the production rate and concentration of MAAs compounds related to photoinduction depend on the phytoplankton community structure, and seasonal changes in UV radiation exert effects on the production and level of MAAs in phytoplankton, especially cyanophyceae. Phytoplankton constantly produces UV-absorbing and photoprotective compounds so as to protect itself against harmful UV radiation, and implements a more effective photoprotective strategy by producing the photoprotective pigment and the UV-absorbing compounds at a distance of time. This study is significant in that a compound-specific stable isotope analysis was applied to the outputs of UV-absorbing compounds and photoprotective pigments by using carbon stable isotope tracer.; 1) Real-time photoprotective response of xanthophyll pigments and mycosporine-like amino acids of Porosira glacialis (Bacillariophycease) This study is an investigation of the newly synthesis of photoprotective compounds by Porosira glacialis in real time using a 13C tracer. Our results show that UV tolerance of P. glacialis was evidenced by the growth rate and chlorophyll a (Chl a) concentration under the UV conditions. The carbon uptake rate indicated that was continuously exposed to photosynthetically active radiation (PAR) for 24 hours, which was higher than that of one exposed to ultraviolet (UV) radiation (UVR). However, it indicated when the exposure time was 72 hours, which was higher than the initial value of P. glacialis exposed to UV radiation and also was higher than that of P. glacialis exposed to PAR. The time difference between the productions of these two compounds clearly reveals the defense strategy used by P. glacialis to synthesize photoprotective compounds (MAAs and DD). The results of this study appear to reflect the synthetic pathways of photoprotective compounds and the carbon cycle within the cell in contrasting patterns over time that are defined by the production of photoprotective pigments (DD) and MAAs.

2) Production of Mycosporine-like amino acids of in situ phytoplankton community in Kongsfjorden, Svalbard, Arctic The spatial distribution of UV-absorbing compounds (Mycosporine-like amino acids, MAAs), was investigated by comparing the phytoplankton community structures in the inner and outer waters of the Kongsfjorden inlet, which is located in arctic Svalbard. Thalassiosira sp. and Phaeocystis sp. were dominant in the outer waters of the Kongfjorden inlet, demonstrating high chlorophyll a (chl a) concentrations and low MAA concentrations in the outer bay waters. However, Kongsfjorden Bay was dominated by Phaeocystis sp. and demonstrated high MAA concentrations despite low chl a concentrations. The carbon fixation rate at a station located inside Kongsfjorden Bay (T05) was significantly photo-inhibited by UV radiation, demonstrating higher production rates of MAA and chl a than at a station (B09) in outer bloom waters. Additionally, the turnover rates of individual MAAs were faster inside the Kongsfjorden Bay than in the outside waters. As a result, the natural phytoplankton community demonstrated different UV adaptation mechanisms according to the phytoplankton species, in this case, Thalassiosira sp. vs. Phaeocystis sp. It is possible to understand real-time changes for newly photosynthesized MAAs as UV-absorbing compounds in the natural phytoplankton community. This takes place via determination of in situ MAA production rates using 13C tracer and High Performance Liquid Chromatography (HPLC) combined with an isotope ratio mass spectrometer (irMS).

3) Relationship of Mycosporine-like amino acids, DMSP and photo-protective pigment of phytoplankton assemblage in Kongsfjorden, Svalbard, Arctic We investigated ultraviolet radiation (UV)-absorbing compounds (mycosproine-like amino acids (MAAs)), photoprotective xanthophylls compounds (diadinoxanthin (DD), diatoxanthin (DT)) and dimethylsulphoniumpropionate (DMSP) for their photoprotective function of phytoplankton. in Kongsfjorden, Svalbard, Arctic springtime. Surface water was collected from the inner bay and offshore of Kongsfjorden on the western side of Svalbard Island in the Subarctic Circle and from waters influenced by the West Spitsbergen Current (WSC). The fucoxanthin to chlorophyll (fuco-chl) ratio was commonly higher in a chlorophyll maximum area (offshore sea), wherefore more diatoms inhabit there. Chl a concentration showed a comparatively higher level in WSC waters. On the other hand, the inner bay which has been relatively low chl a concentration showed a relatively lower fuco-chl ratio and was dominated by phytoplankton, like Phaeocystis sp. and nanoflagellate. Phytoplankton assemblage have been influenced WSC and distinguished dominated phytoplankton species according to region that inner bay represented dominated Phaeocystis sp. and Thalassiosira sp. at offshore. So, our results indicated the relatively different of strategy through the phytoplankton assemblage. UV-absorbing compounds (MAAs) exhibits higher in chlorophyll-specific concentration and the ratio of DD and DT to chlorophyll (DD/DT-chl ratio) tends to be higher in the inner bay. Thus, they seemed to be complementary to each other. However, the ratio of β-DMSP to chlorophyll (DMSP-chl ratio) does not show a distinct spatial distribution due to environmental factors and interspecies specificities. In this study, it was found that photoprotective strategies selectively as to species specificity, but that UV-absorbing compounds and photoprotective pigments are distinctly complementary to each other under natural environments.

4) Seasonal changes in production rates of Mycosporine-like amino acids in relation to phytoplankton species composition in mid-latitude temperate lakes The production rate of mycosporine-like amino acids (MAAs) was calculated using carbon stable isotopes on phytoplankton that was exposed to UV radiation after in situ incubation at the site for one year (every month). In the middle latitudes of the Korean Peninsula, UV radiation reached peak intensity between July and August. In Lake Paldang and Lake Cheongpyeong, diatoms were the dominant species of phytoplankton throughout the year. In Lake Cheongpyeong, the relative abundance of cyanophyceae (Anabaena spiroides) reached over 80% in July. Changes in phytoplankton abundance implies that the phytoplankton community structure is influenced by seasonal changes in the production rate and concentration of MAAs. POM cultured in Lake Paldang secreted the most MAAs during October. The dominance of diatoms in phytoplankton composition suggests that they have a long-term response to UV radiation. POM cultured in Lake Cheongpyeong showed the greatest increase in the production of MAAs in July when UV radiation reached its peak intensity. POM had an immediate response to UV radiation due to the dominance of cyanobacteria that are hypersensitive to UV radiation. The results showed that the production rate and concentration of MAAs compounds related to photoinduction depend on the phytoplankton community structure, and seasonal changes in UV radiation exert effects on the production and level of MAAs in phytoplankton, especially cyanophyceae. Phytoplankton constantly produces UV-absorbing and photoprotective compounds so as to protect itself against harmful UV radiation, and implements a more effective photoprotective strategy by producing the photoprotective pigment and the UV-absorbing compounds at a distance of time. This study is significant in that a compound-specific stable isotope analysis was applied to the outputs of UV-absorbing compounds and photoprotective pigments by using carbon stable isotope tracer.