Genetic characterization of a flap1 null mutation in Arabidopsis npq4 and pgr5 plants suggests that the regulatory role of FLAP1 involves the control of proton homeostasis in chloroplasts

DLDG1, the Arabidopsis Homolog of the Cyanobacterial H+-Extrusion Protein, Regulates Non-Photochemical Quenching in Chloroplasts

“…PxcA interacts with the cyanobacterial FLAP1 homolog, slr0404 (Sato et al, 2007). We reported that Arabidopsis FLAP1 is found in the thylakoid and envelope membrane of chloroplasts and that a flap1 mutant had a greater NPQ value than WT, especially under fluctuating light (Sato et al, 2017;Trinh et al, 2019); the phenotype is similar to those observed in dldg1 (Fig. 4B).…”

“…We screened for Arabidopsis genes that have the following properties: (i) predicted to be chloroplastic, (ii) co-expressed with known NPQ-related genes, and (iii) conserved in oxygenic phototrophs. In addition to FLAP1, the details of which we reported previously (Sato et al, 2017;Trinh et al, 2019), we identified, by reverse genetic screening, another candidate NPQ-related gene at the open-reading frame, At4g31040, which we abbreviated as DLDG1. Examination of the co-expression database ATTEDII (Obayashi et al, 2018) revealed that DLDG1 is co-expressed with NPQ1 (encodes VDE), FTRA2 (ferredoxin-thioredoxin oxidoreductase subunit A), and FNR2 (ferredoxin-NADP + oxidoreductase 2), whose functions seem to be important for controlling NPQ and ΔpH.…”

“…We recently screened for Arabidopsis genes that are co-expressed with NPQ-related genes that are specifically conserved in oxygenic phototrophs; we identified a gene that encodes an uncharacterized NPQ-regulatory protein, which we named Fluctuating-Light Acclimation Protein1 (FLAP1) (Sato et al, 2017). The Arabidopsis flap1 mutant has a larger NPQ value than does the wild type (WT) and has a pale-green leaf phenotype, but only when grown under light of fluctuating intensity (fluctuating light) (Sato et al, 2017;Trinh et al, 2019), indicating that FLAP1 helps plants acclimate to fluctuating light. For the study reported herein, with the use of reverse genetic screening, we identified another open-reading frame, namely Day-Length-dependent Delayed-Greening1 (DLDG1), as a new NPQ-regulatory component specifically conserved in oxygenic phototrophs.…”

Light Quality-Dependent Regulation of Non-Photochemical Quenching in Tomato Plants

“…At the same time, plants grown under monochromatic green light or mixed red–green–blue spectrum had significantly diminished levels of PsbS, cyt f , and PGRL1 protein. The importance of the PsbS and PGR5/PGRL1 complex in NPQ activation was previously documented with npq4 and pgr5 (also pgr1 ) mutants, which are defective in PsbS-dependent NPQ and proton influx from the stroma to the lumen [ 48 ], respectively. Several authors [ 7 , 26 , 47 , 48 , 49 ] have documented that accelerated NPQ formation induced by pre-illumination was absent in npq4 , which presented almost no NPQ formation, while in the pgr1 mutant, the NPQ rise was visibly slowed down and sensitive to DTT feeding [ 26 ].…”

Fluctuating light experiments and semi-automated plant phenotyping enabled by self-built growth racks and simple upgrades to the IMAGING-PAM

“…The extreme sensitivity of pgr5 loss-of-function mutants to fluctuating light has been reported many times by independent groups [25, 26, 29]. The susceptibility is primarily attributed to a malfunctioning cyclic electron flow (CEF) cycle around PSI [20].…”