LHCII is a crucial light-harvesting pigment/protein complex in photosystem II (PSII) supercomplex. It also participates in the light energy redistribution between photosystems and in the photoprotection via its revers...LHCII is a crucial light-harvesting pigment/protein complex in photosystem II (PSII) supercomplex. It also participates in the light energy redistribution between photosystems and in the photoprotection via its reversible dissociation with PSII and PSI (photosystem I). This reversible detachment of LHCII is regulated by phosphorylation of its own and PSII core protein. Under low light conditions, LHCII is phosphorylated and dissociated with PSII core protein complex and combined with PSI, which balances the excitation energy between PSII and PSI;Under high light environment, the phosphorylation of PSII core proteins makes LHCII detach from PSII. The dissociated LHCII presents in a free state, which involves in the thermal dissipation of excess excitation energy. During photodamage, dual phosphorylations of both PSII core proteins and LHCII complexes occur. The phosphorylation of D1 is conductive to the disintegration of photodamaged PSII and the cycle of repair. In this circumstance, the phosphorylation of LHCII is induced by reactive oxygen species (ROS) and then the phosphorylated LHCII migrates to PSI, into the repair cycle of damaged PSII. The ferredoxin (Fdr) and thioredoxin (Tdr) system may play a possible central role in the phosphorylation regulation on LHCII dissociation.展开更多
State transition is an important protection mechanism of plants for maintaining optimal efficiency through redistributing unbalanced excitation energy between photosystem II （PSII） and photosystem I （PSI）. This pr...State transition is an important protection mechanism of plants for maintaining optimal efficiency through redistributing unbalanced excitation energy between photosystem II （PSII） and photosystem I （PSI）. This process depends on the reversible phosphorylation/dephosphorylation of the major light-harvesting complex II （LHCII） and its bi-directional migration between PSII and PSI. But it remains unclear how phosphorylation/dephosphorylation modulates the LHCII conformation and further regulates its reversible migration. Here molecular dynamics simulations （MDS） were employed to elucidate the impact of phosphorylation on LHCII conformation. The results indicated that N-terminal phosphorylation loosened LHCII trimer with decreased hydrogen bond （H-bond） interactions and extended the distances between neighboring monomers, which stemmed from the conformational ad- justment of each monomer itself. Global conformational change of LHCII monomer started from its stromal N- terminal （including the phosphorylation sites） by enhancing its interaction to lipid membrane and by adjusting the interaction network with surrounded inter-monomer andintra-monomer transmembrane helixes of B, C, and A, and finally triggered the reorientation of transmembrane helixes and transferred the conformational change to luminal side helixes and loops. These results further our understanding in molecular mechanism of LHCII migration during state transition from the phosphorylation-induced microstructural feature of LHCII.展开更多
In Arabidopsis thaliana, STN7 kinase is required for phosphorylation of LHCII and for state transitions. In this paper, a hydrophilic polypeptide, derived from the amino acid sequence of STN7, was conjugated to a carr...In Arabidopsis thaliana, STN7 kinase is required for phosphorylation of LHCII and for state transitions. In this paper, a hydrophilic polypeptide, derived from the amino acid sequence of STN7, was conjugated to a carrier protein, bovine serum albumin (BSA), to obtain the polyclonal antibody. Immunogenicity and specificity of the polyclonal antibody were evaluated by agar gel immunodiffusion (AGID) test and Western blot analysis. The results show that besides the phosphorylation of LHCII proteins, also the expression of STN7 was regulated by temperature conditions. In addition, the change tendency of LHCII proteins phosphorylation was not only coherent with expression of STN7 with respect to increasing temperature, but also closely related to state transitions. These results would provide useful information for studying regulatory mechanism of LHCII proteins phosphorylation and expression of STN7.展开更多
Seagrasses are marine flowering plants that perform oxygenic photosynthesis both under high,white sunlight and under low,blue-green light,conditions fundamentally different from those experienced by land plants.Thus f...Seagrasses are marine flowering plants that perform oxygenic photosynthesis both under high,white sunlight and under low,blue-green light,conditions fundamentally different from those experienced by land plants.Thus far,the adaptation of seagrass photosynthetic machinery to this underwater light gradient remains poorly understood.Here,we investigate the Mediterranean seagrass Posidonia oceanica,an ecosystem engineer thriving from the surface down to 40 m depth,to uncover how it maintains efficient photosynthesis across this gradient.Combining spectroscopy with pigment and blue native-PAGE analysis,we show that P.oceanica maintains a high but stable photosystem I(PSI)/PSII ratio and constant antenna size at all depths,in conjunction with a high abundance of light-harvesting complex II(LHCII).Electron microscopy observation indicated that adjustment of photosynthetic efficiency along the depth gradient is primarily achieved through structural remodeling of thylakoid architecture,rather than major changes in photosystem composition.We also identify a previously undescribed large PSI supercomplex(L-PSI-LHCII)that binds an additional Lhca1-Lhca4 dimer and a phosphorylated LHCII trimer.This complex,expressed at all tested depths,is enriched in chlorophyll b,lacks the far-red-absorbing chlorophylls(red forms)typical of land plants,and exhibits distinct energy-transfer dynamics optimized for blue-light harvesting.The presence of similar PSI supercomplex in other marine seagrasses,such as Zostera marina,suggests a conserved strategy among deep-growing species.Collectively,these results reveal how seagrasses combine structural adaptation at the level of PSI with thylakoid architecture reorganization to sustain efficient photosynthesis and long-term carbon fixation under blue-dominated marine light.展开更多
文摘LHCII is a crucial light-harvesting pigment/protein complex in photosystem II (PSII) supercomplex. It also participates in the light energy redistribution between photosystems and in the photoprotection via its reversible dissociation with PSII and PSI (photosystem I). This reversible detachment of LHCII is regulated by phosphorylation of its own and PSII core protein. Under low light conditions, LHCII is phosphorylated and dissociated with PSII core protein complex and combined with PSI, which balances the excitation energy between PSII and PSI;Under high light environment, the phosphorylation of PSII core proteins makes LHCII detach from PSII. The dissociated LHCII presents in a free state, which involves in the thermal dissipation of excess excitation energy. During photodamage, dual phosphorylations of both PSII core proteins and LHCII complexes occur. The phosphorylation of D1 is conductive to the disintegration of photodamaged PSII and the cycle of repair. In this circumstance, the phosphorylation of LHCII is induced by reactive oxygen species (ROS) and then the phosphorylated LHCII migrates to PSI, into the repair cycle of damaged PSII. The ferredoxin (Fdr) and thioredoxin (Tdr) system may play a possible central role in the phosphorylation regulation on LHCII dissociation.
基金supported by the National Key Basic Research Foundation of China(2006CB910303 and 2011CB710904)the National Natural Science Foundation of China(11072251 and31230027)+1 种基金the CAS Knowledge Innovation Program(KJCX2YW-L08)the Scientific Research Equipment Project(Y2010030)
文摘State transition is an important protection mechanism of plants for maintaining optimal efficiency through redistributing unbalanced excitation energy between photosystem II （PSII） and photosystem I （PSI）. This process depends on the reversible phosphorylation/dephosphorylation of the major light-harvesting complex II （LHCII） and its bi-directional migration between PSII and PSI. But it remains unclear how phosphorylation/dephosphorylation modulates the LHCII conformation and further regulates its reversible migration. Here molecular dynamics simulations （MDS） were employed to elucidate the impact of phosphorylation on LHCII conformation. The results indicated that N-terminal phosphorylation loosened LHCII trimer with decreased hydrogen bond （H-bond） interactions and extended the distances between neighboring monomers, which stemmed from the conformational ad- justment of each monomer itself. Global conformational change of LHCII monomer started from its stromal N- terminal （including the phosphorylation sites） by enhancing its interaction to lipid membrane and by adjusting the interaction network with surrounded inter-monomer andintra-monomer transmembrane helixes of B, C, and A, and finally triggered the reorientation of transmembrane helixes and transferred the conformational change to luminal side helixes and loops. These results further our understanding in molecular mechanism of LHCII migration during state transition from the phosphorylation-induced microstructural feature of LHCII.
基金the National Natural Sciences Foundation of China (Grant No. 30270124)Doctoral Foundation of Ministry of Education of China (Grant No. 20020610094)+1 种基金Program for New Century Excellent Talents in University (Grant No. NCET-04-0861)Sichuan University Research Grant 985
文摘In Arabidopsis thaliana, STN7 kinase is required for phosphorylation of LHCII and for state transitions. In this paper, a hydrophilic polypeptide, derived from the amino acid sequence of STN7, was conjugated to a carrier protein, bovine serum albumin (BSA), to obtain the polyclonal antibody. Immunogenicity and specificity of the polyclonal antibody were evaluated by agar gel immunodiffusion (AGID) test and Western blot analysis. The results show that besides the phosphorylation of LHCII proteins, also the expression of STN7 was regulated by temperature conditions. In addition, the change tendency of LHCII proteins phosphorylation was not only coherent with expression of STN7 with respect to increasing temperature, but also closely related to state transitions. These results would provide useful information for studying regulatory mechanism of LHCII proteins phosphorylation and expression of STN7.
基金supported by the Swedish Foundation for Strategic Research(SSF.grant number ARC19-0051).
文摘Seagrasses are marine flowering plants that perform oxygenic photosynthesis both under high,white sunlight and under low,blue-green light,conditions fundamentally different from those experienced by land plants.Thus far,the adaptation of seagrass photosynthetic machinery to this underwater light gradient remains poorly understood.Here,we investigate the Mediterranean seagrass Posidonia oceanica,an ecosystem engineer thriving from the surface down to 40 m depth,to uncover how it maintains efficient photosynthesis across this gradient.Combining spectroscopy with pigment and blue native-PAGE analysis,we show that P.oceanica maintains a high but stable photosystem I(PSI)/PSII ratio and constant antenna size at all depths,in conjunction with a high abundance of light-harvesting complex II(LHCII).Electron microscopy observation indicated that adjustment of photosynthetic efficiency along the depth gradient is primarily achieved through structural remodeling of thylakoid architecture,rather than major changes in photosystem composition.We also identify a previously undescribed large PSI supercomplex(L-PSI-LHCII)that binds an additional Lhca1-Lhca4 dimer and a phosphorylated LHCII trimer.This complex,expressed at all tested depths,is enriched in chlorophyll b,lacks the far-red-absorbing chlorophylls(red forms)typical of land plants,and exhibits distinct energy-transfer dynamics optimized for blue-light harvesting.The presence of similar PSI supercomplex in other marine seagrasses,such as Zostera marina,suggests a conserved strategy among deep-growing species.Collectively,these results reveal how seagrasses combine structural adaptation at the level of PSI with thylakoid architecture reorganization to sustain efficient photosynthesis and long-term carbon fixation under blue-dominated marine light.
