Ycf10 and DLDG1 are homologous proteins located in the chloroplast envelope and encoded by the chloroplast and nuclear genomes, respectively. These two homologs are specifically conserved in organisms that perform oxygenic photosynthesis. Our previous studies have suggested that they are involved in the regulation of photosynthesis, particularly ATP synthesis and thermal dissipation of excess light energy absorbed by chlorophyll, through proton transport between the chloroplast and cytosol.

In this study, we took advantage of recently developed chloroplast genome-editing technology to isolate Arabidopsis ycf10 single and ycf10-dldg1 double mutants and investigated the functions and functional redundancy of these proteins.

When grown under continuous light, these mutants exhibited a pale-green phenotype, which was interestingly rescued by the addition of NaCl to the growth medium. Both the single and double mutants also showed enhanced thermal dissipation compared with the wild type, with a particularly pronounced effect in the double mutant. In addition, the mutants showed reduced stomatal opening and sugar accumulation.

These findings demonstrate that Ycf10 and DLDG1 act cooperatively to maintain proton/ion and pH homeostasis in chloroplasts, thereby supporting efficient photosynthesis and plant growth.

This work was conducted in collaboration with researchers at the University of Copenhagen and other institutions.

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