Prof. Chanhong Kim and his research team from the Shanghai Center for Plant Stress Biology of Chinese Academy of Sciences have disclosed the long-standing research question, i.e., the underlying mechanism of the mode of action of singlet oxygen (1O2) sensor EXECUTER1 protein. This study was published in Nature Communications.
The signaling role of 1O2 generated via free tetrapyrrole molecules (such as chlorophyll) was first reported by Prof. Klaus Apel and colleagues (Wagner et al., 2004 Science). The subsequent forward genetic study has revealed that a nuclear-encoded chloroplast protein EXECTUER1 (EX1) mediates the retrograde signaling upon release of 1O2 in chloroplasts. Even though this finding completely changed the classical view of 1O2, from toxic to signaling molecule, it has been unclear how EX1 protein senses of and reacts to 1O2.
In this study, Prof. Kim's team proposed an exciting proposition that oxidative post-translational modification of Trp643 [located in the DUF3506 domain of EX1; now dubbed singlet oxygen sensor (SOS) domain] is an integral part of 1O2 sensing. This Trp643 oxidation by 1O2 appears to promote EX1 degradation through the membrane-bound FtsH metalloprotease.
The finding also suggests the possibility of a probable release of a genuine signaling molecule during EX1 degradation, which needs to be elucidated to delineate the entire mode of action of EX1 towards 1O2.
Figure: EX1-mediated 1O2 signaling (Image by the research group)
Research groups led by Prof. Klaus Apel from Boyce Thompson Institute at Cornell University in New York, Ithaca and by Prof. Chanhong Kim at Shanghai Center for Plant Stress Biology, Shanghai Institutes for Biological Sciences of Chinese Academy of Sciences have recently addressed a question about how chloroplast-generated 1O2, one of the reactive oxygen species (ROS), activates distinct retrograde signaling cascades via: volatile signaling molecules and EX1, a nuclear-encoded and plastid-targeted protein.
Astaxanthin has excellent antioxidant properties and is widely used in food supplements. Researchers led by Prof. HUANG Qing from the Hefei Institutes of Physical Science have proposed a new method to evaluate the antioxidant activity of astaxanthin isomers against singlet oxygen.
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