The C-terminal cysteine-rich motif of NYE1/SGR1 is indispensable for its function in chlorophyll degradation in Arabidopsis
The C-terminal cysteine-rich motif of NYE1/SGR1 affects chlorophyll degradation likely by mediating its self-interaction and conformational change, and somehow altering its Mg-dechelating activity in response to the changing redox potential.
During green organ senescence in plants, the most prominent phenomenon is the degreening caused by net chlorophyll (Chl) loss. NON-YELLOWING1/STAY-GREEN1 (NYE1/SGR1) was recently reported to be able to dechelates magnesium (Mg) from Chl a to initiate its degradation, but little is known about the domain/motif basis of its functionality. In this study, we carried out a protein truncation assay and identified a conserved cysteine-rich motif (CRM, P-X3-C-X3-C-X-C2-F-P-X5-P) at its C terminus, which is essential for its function. Genetic analysis showed that all four cysteines in the CRM were irreplaceable, and enzymatic assays demonstrated that the mutation of each of the four cysteines affected its Mg-dechelating activity. The CRM plays a critical role in the conformational change and self-interaction of NYE1 via the formation of inter- and intra-molecular disulfide bonds. Our results may provide insight into how NYE1 responds to rapid redox changes during leaf senescence and in response to various environmental stresses.
KeywordsArabidopsis Chlorophyll degradation NYE1/SGR1 Cysteine-rich motif Redox regulation
We are grateful to Jianxiang Liu for sharing pXY103 and pXY104 vectors, and Tongshui Zhou and Guojun Zhou for technical assistance on HPLC analysis. This work was supported by grants from the National Natural Science Foundation of China (31670287) to BK, the Science and Technology Commission of Shanghai Municipality (15JC1400800) to GR and the Swiss National Science Foundation (31003A_172977) to SH.
Conceived and designed the experiments: BK, GR, SH, ZX, JC. Performed the experiments: ZX, SW, JC, XZhu. Analyzed the data: ZX, JC. Contributed reagents/materials/analysis tools: XZho, SH. Wrote the paper: BK, GR, ZX, JC, SH, XZhu.
This work was supported by grants from the National Natural Science Foundation of China (31670287) to BK, the Science and Technology Commission of Shanghai Municipality (2015JC1400800) to GR, and the Swiss National Science Foundation (31003A_172977) to SH.
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