Lack of plastid‐encoded Ycf10, a homolog of the nuclear‐encoded DLDG1 and the cyanobacterial PxcA, enhances the induction of non‐photochemical quenching in tobacco

Abstract

pH homeostasis in the chloroplast is crucial for the control of photosynthesis and other metabolic processes in plants. Recently, nuclear-encoded Day-Lengthdependent Delayed Greening1 (DLDG1) and Fluctuating-Light Acclimation Protein1 (FLAP1) that are required for the light-inducible optimization of plastidial pH in Arabidopsis thaliana were identified. DLDG1 and FLAP1 homologs are specifically conserved in oxygenic phototrophs, and a DLDG1 homolog, Ycf10, is encoded in the chloroplast genome in plant cells. However, the function of Ycf10 and its physiological significance are unknown. To address this, we constructed ycf10 tobacco Nicotiana tabacum mutants and characterized their phenotypes. The ycf10 tobacco mutants grown under continuous-light conditions showed a pale-green phenotype only in developing leaves, and it was suppressed in short-day conditions.The ycf10 mutants also induced excessive non-photochemical quenching (NPQ) compared with those in the wild-type at the induction stage of photosynthesis.These phenotypes resemble those of Arabidopsis dldg1 mutants, suggesting that they have similar functions. However, there are distinct differences between the two mutant phenotypes: The highly induced NPQ in tobacco ycf10 and the Arabidopsis dldg1 mutants are diminished and enhanced, respectively, with increasing duration of the fluctuating actinic-light illumination. Ycf10 and DLDG1 were previously shown to localize in chloroplast envelope-membranes, suggesting that Ycf10 and DLDG1 differentially control H + exchange across these membranes in a light-dependent manner to control photosynthesis.

Chloroplast pH Homeostasis for the Regulation of Photosynthesis

“…Researchers hypothesized that H + extrusion regulated by Ycf10/CemA is important in the acidification of intermembrane spaces for the conversion of HCO 3 − to CO 2 , which in turn accelerates the diffusion of CO 2 into the chloroplasts ( Rolland et al, 1997 ). Tobacco ycf10 loss-of-function mutants also showed excessive induction of NPQ, similar to that observed in Arabidopsis dldg1 mutants ( Trinh et al, 2021 ). However, g H + increased in ycf10 mutants but decreased in dldg1 mutants ( Harada et al, 2019 ; Trinh et al, 2021 ).…”

“…Tobacco ycf10 loss-of-function mutants also showed excessive induction of NPQ, similar to that observed in Arabidopsis dldg1 mutants ( Trinh et al, 2021 ). However, g H + increased in ycf10 mutants but decreased in dldg1 mutants ( Harada et al, 2019 ; Trinh et al, 2021 ). Furthermore, NPQ decreases in ycf10 and increases in dldg1 mutants with the increase in the duration of fluctuating light conditions ( Harada et al, 2019 ; Trinh et al, 2021 ).…”

“…Collectively, these results suggest that DLDG1 and Ycf10 distinctively control H + extrusion in chloroplasts ( Trinh et al, 2021 ). Complementation assays of E. coli antiporter mutants suggest functional interaction between DLDG1 and Ycf10 for controlling Na + extrusion and K + uptake ( Trinh et al, 2021 ).…”

“…Furthermore, NPQ decreases in ycf10 and increases in dldg1 mutants with the increase in the duration of fluctuating light conditions ( Harada et al, 2019 ; Trinh et al, 2021 ). Collectively, these results suggest that DLDG1 and Ycf10 distinctively control H + extrusion in chloroplasts ( Trinh et al, 2021 ). Complementation assays of E. coli antiporter mutants suggest functional interaction between DLDG1 and Ycf10 for controlling Na + extrusion and K + uptake ( Trinh et al, 2021 ).…”

Reactive Oxygen Species Initiate Defence Responses of Potato Photosystem II to Sap-Sucking Insect Feeding

“…Under almost all kinds of stresses, the light energy absorbed by PSII and PSI overdoes the amount that can be used for photochemistry, resulting in an increased formation of reactive oxygen species (ROS), such as singlet oxygen ( 1 O 2 ), superoxide anion radical (O 2 •− ), and hydrogen peroxide (H 2 O 2 ) [ 20 , 21 , 22 , 23 , 24 , 25 , 26 ]. In order to avoid photoinhibition, mainly of PSII [ 27 , 28 , 29 , 30 , 31 , 32 , 33 ], PSI photoinhibition is, to a minor level, likely to occur [ 33 , 34 ]. Plants have developed various mechanisms to control the absorbed light energy [ 35 , 36 ].…”