Natural genetic variation for regulation of photosynthesis response to light in Arabidopsis thaliana

Abstract

Plants are known to be able to acclimate their photosynthesis to the level of irradiance.Here we present the analysis of natural genetic variation for photosynthetic light use efficiency (ΦPSII) in response to five light environments among 12 genetically diverse Arabidopsis thaliana accessions. We measured acclimation of ΦPSII to constant growth irradiances of four different levels (100, 200, 400, and 600 µmol m -2 s -1 ) by imaging chlorophyll fluorescence after 24 days of growth, and compared these results to acclimation of ΦPSII to a step-wise change in irradiance where the growth irradiance was increased from 100 to 600 µmol m -2 s -1 after 24 days of growth. Genotypic variation for ΦPSII is shown by calculating heritability for short-term ΦPSII response to different irradiance levels, as well as for the relation of ΦPSII measured at light saturation (a measure of photosynthetic capacity) to growth irradiance level, and for the kinetics of the response to a step-wise increase in irradiance from 100 to 600 µmol m -2 s -1 . A genomewide association study for ΦPSII measured one hour after a step-wise increase in irradiance identified several new candidate genes controlling this trait. In conclusion, the different photosynthetic responses to a changing light environment displayed by different Arabidopsis accessions are due to genetic differences, and we have identified candidate genes for the photosynthetic response to an irradiance change. The genetic variation for photosynthetic acclimation to irradiance found in this study will allow future identification and analysis of the causal genes for the regulation of ΦPSII in plants. Abbreviations: PSI -photosystem I; PSII -photosystem II; LHC -light harvesting complex; Fominimum fluorescence yield in dark-adapted state; Fm -maximum fluorescence yield in dark-adapted state; Fm' -maximum fluorescence yield in light-adapted state; Fv/Fmmaximum photosynthetic light use efficiency of PSII in dark-adapted state; ΦPSIIoperating photosynthetic light use efficiency of PSII in light-adapted state; rETR -relative electron transport rate; NPQ -non-photochemical quenching; qP -co-efficient of photochemical quenching of chlorophyll fluorescence (PSII efficiency facor); Fv'/Fm'photosynthetic light use efficiency of the open PSII reaction centres in light-adapted state