Recently, a team led by academician of the Chinese Academy of Sciences, researcher of the Institute of Botany, Chinese Academy of Sciences, Tingyun Kuang, and researcher Jianren Shen cooperated with researchers from Jinan University and Tsinghua University revealed an important photosynthetic membrane protein super complex of Pseudomonas aeruginosa – photosystem I light-harvesting complex. I. (PSI-LHCI) 3.49 resolution structure. This study further improved the understanding of the trend of light system structure changes during the evolution of photosynthetic organisms, also provides a new theoretical basis and new ideas for artificially stimulating the photosynthesis mechanism, guiding the design of crops and improving the light energy utilization efficiency of plants. Related results have been published in the journal of Nature Plants.

 

Pseudomonas aeruginosa is a large green algae that grows in the intertidal zone. During the high tide, the algae grow in the low light environment dominated by blue-green light and green light and can complete the process of energy absorption and energy transfer to meet the needs of its own growth. It has light protection and can adapt to the exposed high light intensity environment at low tide, and has unique photosynthesis characteristics.

 

 

The researchers used cryo-electron microscopy to analyze their PSI-LHCI structure. The study found that PSI-LHCI of Pseudomonas aeruginosa has 13 core complex subunits and 10 light-harvesting antenna complexes, which is the biggest amount in reported PSI-LHCI structure. The arrangement of the 10 light-harvesting antenna complexes presents a special double-ring pattern, which reflects the adaptation of Pseudomonas aeruginosa to a weaker light environment. Compared with higher plants, the rate of excitation energy transmission of Pseudomonas aeruginosa is faster, which also confirms that higher plants living on land pay a certain price for energy transfer rate in adapting to the strong light environment.

 

The researchers have long been committed to the study of the structure and function of photosynthetic membrane proteins. Previously, high-resolution structures of PSI supercomplexes such as peas and red algae have been analyzed. This is another major breakthrough the team has made in the field of PSI structure and function research. The journal of Nature Plants also reported the PSI-LHCI complex structure of Chlamydomonas, another green algae analyzed by the research team of the Institute of Biophysics of the Chinese Academy of Sciences which highlights the world’s leading position in the field of photosynthetic membrane protein structure analysis.

 

It is known that Photosystem I (PSI) is a highly efficient light energy absorption and conversion system with a quantum conversion efficiency of over 90%. Therefore, the structural basis of PSI’s efficient energy absorption and energy transfer has attracted the attention of scientists. At present, prokaryotic cyanobacteria, eukaryotic red algae, and higher plant PSI structures have been resolved, but the research related to the high-resolution structure of green algae PSI is still in the process.

 

 

Reference

Xiaochun Qin, Xiong Pi, Wenda Wang, et al. Structure of a green algal photosystem I in complex with a large number of light-harvesting complex I subunits, Nature Plants 5(3):263-272 · March 2019, DOI: 10.1038/s41477-019-0379-y