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Table of Content

    25 June 2021, Volume 43 Issue 3
    Previous Issue   
    Review Article
    Fucoxanthin chlorophyll a/c-binding proteins in diatoms: Deciphering red lineage of light-harvesting complex 
    ZHAO Songhao, TAO Qiushuang, SHEN Jianren, WANG Wenda
    2021, 43(3):  157-164.  doi:10.3969/j.issn.0253-9608.2021.03.001
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    Diatoms are an important group of red phytoplankton in the ocean and contribute about 40% of marine or 20% of the global primary productivity, playing significant roles in global carbon fixation and geochemical cycle. An important factor that contributes to the ecological success of diatoms is their fucoxanthin (Fx) chlorophyll (Chl) a/c-binding proteins (FCPs), which have exceptional capabilities in light harvesting and adaptation. To study efficient blue-green light harvesting, energy transfer and conversion in diatoms under water, our research team collaborated with coworkers and solved a crystal structure of FCP-type light-harvesting complex and a cryo-electron microscopic structure of photosystem II-FCPII supercomplex from diatoms. These two structures reveal unique structural properties and aggregated states of FCP antennae, as well as the details of chlorophylls a, chlorophylls c and fucoxanthin pigments they bound, thus providing the solid basis for deciphering the highly efficient light-energy utilization mechanism of the photosynthetic machinery in diatoms.
    Advances in structural biology of photosystem complexes in higher plants
    SU Xiaodong, LI Mei
    2021, 43(3):  165-175.  doi:10.3969/j.issn.0253-9608.2021.03.002
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     Plants convert absorbed solar energy into chemical energy and release oxygen through photosynthesis, a process performed by several protein supercomplexes, including photosystem II and photosystem I. Both photosystems are membrane-embedded proteinpigment supercomplexes, consisting of the core complex and the peripheral antennae system. The two photosystems show dynamic structural feature that contributes to the adaptation and acclimation of plants under different light conditions. Structural information of these supercomplexes provides the basis for deeper understanding the molecular mechanism of photosynthesis. In this paper, we summarized the recent research progress on the structural analysis of photosystems II and I, and related protein complexes from higher plants.
    Structures and key bilins of red algal phycobilisomes
    XIAO Yanan, MA Jianfei, YOU Xin, SUI Senfang
    2021, 43(3):  176-188.  doi:10.3969/j.issn.0253-9608.2021.03.003
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    Phycobilisomes are large water-soluble light-harvesting complexes in red algae and cyanobacteria, with the energy transfer efficiency higher than 95%. The high-resolution structures of phycobilisomes resolved so far are from the red algae Griffithsia pacifica and Porphyridium purpureum, providing important information of the overall structures of the phycobilisomes, especially the structures and functions of linker proteins. Furthermore, linker proteins regulate the energy state of chromophores in Porphyridium purpureum phycobilisome. In this review, we analyze the overall structures of red algal phycobilisomes and the microenvironments of key chromophores.
    Atomic structure of the photosynthetic reaction center from a green sulfur bacterium
    CHEN Jinghua, KUANG Tingyun, SHEN Jianren, ZHANG Xing
    2021, 43(3):  189-198.  doi:10.3969/j.issn.0253-9608.2021.03.004
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    Green sulfur bacteria are strictly anaerobic photosynthetic bacteria, and perform anoxygenic photosynthesis by obtaining electrons from sulfides. The photosynthetic light-reaction system of green sulfur bacteria consists of a peripheral light-harvesting antenna called chlorosome, an energy transmitter FMO protein and the reaction center complex. In this paper, we describe the atomic structure of the FMO-reaction center complex from a green sulfur bacterium solved by cryo-electron microscopy, insight into the energy transfer mechanism within the complex based on the structure obtained, and their implications on the evolution of early photoreaction systems.
    Photosynthetic oxygen-evolving reaction
    ZHANG Chunxi
    2021, 43(3):  199-208.  doi:10.3969/j.issn.0253-9608.2021.03.005
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    Photosynthetic oxygen-evolving center in photosystem II (PSII) of plant is a unique biological catalyst that catalyzes the water oxidation into electrons, protons and dioxygen in high efficiency and high safety using solar energy. Its synthesis, structure and
    catalytic mechanism are great challenge in photosynthetic research. Recently, the high-resolution crystal structure of PSII has revealed the detailed structure of the unique Mn4CaO5-cluster of this natural catalyst. This advance provides a solid basis for the further investigation of the catalytic mechanism of photosynthetic oxygen-evolving reaction at an atom level, which is also a blueprint for the chemical synthesis of the OEC in laboratory. We have succeeded in synthesizing a series of artificial Mn4CaO4-clusters that closely mimic both the structure and physicochemical properties of the natural OEC in PSII. These synthetic Mn4CaO4-clusters provide a good chemical model to investigate the catalytic mechanism of the OEC and open a new direction for the development of high efficiency and low-cost artificial catalysts for the water-splitting reaction in future. Notably, there are still many scientific questions urgent to be answered in both natural and artificial photosynthetic oxygen evolution.
    Progress
    Interpret the latest parameter measurement results of Cygnus X-1
    ZHAO Xueshan, FENG Ye, GOU Lijun
    2021, 43(3):  209-216.  doi:10.3969/j.issn.0253-9608.2021.03.006
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    Cygnus X-1 discovered in 1964 was the first stellar mass black hole that has ever been observed, which continues to fascinate astronomers. Accurate measurements of the systematical parameters will help astronomers better understand its physical properties and put better limits on the evolution of stars. In 2011, the mass, distance, spin and other parameters of this system were comprehensive measured for the first time. In 2021, an international team including researchers from NAOC again made precise measurements and updated all the systematical parameters of Cygnus X-1. In this paper, we introduce the methods for measuring the mass, distance and spin of Cygnus X-1, present results of two previous precise measurements made in 2011 and 2021, respectively, and discuss the implications of the latest measurements on the stellar and binary evolution.
    Application of infrared technique for scientific conservation of cultural relics
    ZHANG Yue, HUANG Jizhong
    2021, 43(3):  217-224.  doi:10.3969/j.issn.0253-9608.2021.03.007
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    Non-destructive testing is one of the important aspects in scientific conservation of cultural relics, where infrared technique has been extensively adopted due to many advantages such as non-intact, non-destructive, high efficiency, wide applicability and safety. A brief introduction about the theory and characteristics of infrared technique is given. By reviewing the latest achievements obtained by infrared photography, infrared spectroscopy and infrared thermography, it shows that infrared technique is very effective in characterizing the image features, internal structures as well as physical and chemical properties of cultural relics. Infrared technique can not only reveal the hidden information about value, technology, pathology and repair history of various types of cultural relics, but also provide qualitative even quantitative reference for their scientific recognition and conservation, which displays a wide prospect in application.
    Overview on the origin of land plants
    WU Zhen, CHENG Shifeng
    2021, 43(3):  225-231.  doi:10.3969/j.issn.0253-9608.2021.03.008
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    The transition of the algal ancestor of land plants from fresh water to land is important in the study of plant evolutionary biology, which has also changed the terrestrial ecosystem of the earth but the evolutionary mechanism of plant terrestrialization remains unknown. The recent report of high-quality reference genomes of several streptophyte algae and one hornwort sheds light on this major event. Based on these studies, we can draw the following conclusions: ①Zygnematophyceae was found to be the closest sister group to the common ancestor of land plants found so far; ②The acquisition of GRAS and PYL genes from soil bacteria via horizontal gene transfer plays an important role in driving the adaptive process of plant terrestrialization; ③The terrestrialization of plant ancestors is an asymptotic evolutionary process, and the genetic material has gone through a series of pre-adaptation processes, which many gene families previously thought to be unique to land plants exist in more primitive green algae; ④Genomics is an important method for studying terrestrialization and its reversibility process (such as some aquatic angiosperms). The molecular mechanism of the adaptive process of plant terrestrialization is still one of the current research hotspots, including artificial design of “experimental evolution”, horizontal gene transfer, a natural transgenic engineering event, and its key role in plant evolution and adaptation. 
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