Abstract Rapid fluctuations in light intensity require swift regulatory adjustments of photosynthesis. Although the major plant regulators of fast photosynthetic responses have been identified, additional genes with conditional or subtle effects are likely still undiscovered. We hypothesized that genes co‐expressed with the core regulators PGR5 , KEA3 , STN7 and ZEP also participate in photosynthetic regulation. Transcriptome co‐expression analysis defined a set of ‘ CERP ’ ( CO‐EXPRESSED‐WITH‐REGULATION‐OF‐PHOTOSYNTHESIS ) candidate genes. Arabidopsis thaliana T‐DNA insertion mutants for selected CERP loci were isolated. Spectroscopic measurements of whole plants and isolated thylakoid membranes, pigment analyses, native/denaturing gel electrophoresis coupled with immunoblotting and fluorescence microscopy were used to assess photosynthetic parameters under constant light and under rapidly fluctuating light regimes and determine photosynthetic complex composition, as well as localize the proteins. Two mutants showed alterations in non‐photochemical quenching (NPQ) during light fluctuations. Mutants lacking CERP1, also known as AAF, showed delayed NPQ relaxation after high‐to‐low light transitions. Mutants lacking CERP4b , also known as FLAP1 , exhibited a higher NPQ during high light phases. These NPQ phenotypes were linked to changes in leaf pigment content and composition. Further characterization of CERP4b/FLAP1 points towards a function of this protein in the formation or composition of the PSII supercomplex. Co‐expression mining successfully uncovered additional components that contribute to rapid photoprotective acclimation. CERP1/AAF is essential for fast NPQ relaxation, while CERP4b/FLAP1 contributes to NPQ in high light, likely through effects on PSII antenna. These findings broaden the known regulatory network governing NPQ by including two components that modulate leaf pigment content and composition.
Keller et al. (Mon,) studied this question.