Fu Aigen's team at Northwestern University revealed the molecular mechanism of Chlamydomonas reinin's resistance to bright light

Recently, Professor Fu Aigen of Northwest University published a report entitled "Immunophilin CYN28 is required for accumulation of photosystem II and thylakoid FtsH protease in Chlamydomonas" online in Plant Physiology The paper is the first to report a molecular mechanism
by which the pro-immune protein CYN28, localized in the thylakoid lumen, is involved in Chlamydomonas against high light.

Pro-proteins are evolutionarily very conserved protein families
.
There are a large number of chloroplast thyroidoid lumen in higher plants and Chlamydomonas reininthine, with unknown function.

This study found that Chlamydomonas reintifoli CYN28 knockout mutant had a typical highlight-sensitive phenotype, with reduced photosystem II accumulation and impaired
photosystem II repair under bright light.
In vivo and in vitro biochemical experiments showed that CYN28 had peptidyl prolyl cis- and trans-isomerase (PPIase) activity, and arginine at the 187th position of the conserved site determined its enzymatic activity, which in turn affected the physiological function
of CYN28.
The team further used co-immunoprecipitation and protein profiling to identify thylakoid FtsH protease as a downstream target of CYN28, and proved that FtsH N'telproline is the site of action of CYN28
.
Deletion of CYN28 or mutation of FtsH N' teloproline can impair
FtsH protease turnover under bright light.
Thylakoid membrane FtsH is one of
the AAA family proteases involved in photosystem II damage repair.
Previous studies have shown that mutants of Chlamydomonas reinhardi with reduced FtsH expression in photosynthetic organisms also have similar high-light-sensitive phenotypes, while overexpression of FtsH can enhance the ability of Chlamydomonas to resist bright light (Wang et al.
, 2017; Malnoë et al.
, 2014）
。

In summary, this study reveals that the prophilic protein CYN28 is involved in the high-light resistance
of Chlamydomonas reinfield by affecting the accumulation of photosystem II and assisting the repair of photosystem II by participating in the turnover under FtsH high light.

Weihan Fu, a 2019 master's student in the School of Life Sciences of Northwest University, is the first author of the paper, and Professor Fu Aigen and Associate Professor Faye Wong of the School of Life Sciences, Northwest University are the co-corresponding authors
of the paper.
The research was supported
by the National Natural Science Gene, the Science and Technology Department of Shaanxi Province, and the university-level scientific research start-up fund of Northwest University.