Light is essential for photosynthetic organisms, including higher plants and cyanobacteria, by providing energy for photosynthesis. Light can regulate cellular processes by modulating protein expression at the transcriptional or posttranscriptional level. Protein degradation, a crucial process controlling protein quality, is also regulated by light. The significance of the light-regulated protein degradation is exemplified by the well-established light-induced degradation and repair of the photosystem II reaction center D1 protein in photosynthetic organisms. However, systematic studies of light-regulated protein degradation events in photosynthetic organisms are lacking.
Recently, Prof. WANG Yingchun's group from the Institute of Genetics and Developmental Biology (IGDB) of the Chinese Academy of Sciences reported their study about the large-scale identification of protein degradation under light or dark conditions in the model cyanobacterium Synechocystis sp. PCC 6803.
In this study, by using a quantitative proteomics method, the researchers revealed that 79 proteins displayed light-regulated degradation including proteins involved in photosystem II structure or function, quinone binding and NAD(P)H dehydrogenase. Among these, 25 proteins were strongly dependent on light for degradation. Moreover, 31 proteins displayed dark-regulated degradation and 71 proteins displayed significant degradation in both light and dark were also identified.
Interestingly, the researchers found that the light-dependent degradations of multiple proteins were sensitive to redox status of the overall intracellular environment and the plastoquinone (PQ) pool, the latter is an integral part of the photosynthetic electron transport chain on the cyanobacteria thylakoid membrane. Degradation of these proteins was favored by more reduction and inhibited by more oxidation.
These findings will serve as an important resource for future studies aimed at understanding light-regulated processes and protein quality control mechanisms in cyanobacteria.
It was funded by the Ministry of Science and Technology of China and the National Natural Science Foundation of China.
Systematic identification of the light/dark-dependent protein degradation events in cyanobacteria by quantitative proteomics technique (Image by IGDB)
Contact:
Dr. WANG Yingchun
Institute of Genetics and Developmental Biology, Chinese Academy of Sciences
Email: ycwang@genetics.ac.cn
