Chloroplast Accumulation Enhances Photosynthesis and Biomass Production

Light-induced chloroplast movement is one of the most important responses for utilization of photosynthetic light. Chloroplasts move toward weak light-irradiated areas to efficiently absorb light (the accumulation response), whereas they move away from excess light to avoid photodamage (the avoidance response). In Arabidopsis thaliana, the accumulation response is regulated by phototropin1 (phot1) and photoropin2 (phot2), whereas the avoidance response is mainly regulated by phot2. Using various Arabidopsis mutants deficient in chloroplast movement, Gotoh et al. (10.1104/pp.18.00484) demonstrate that the accumulation response enhances leaf photosynthesis and plant biomass production. Conspicuously, phototropin2 mutant plants specifically defective in the avoidance response but not in other phototropin-mediated responses displayed a constitutive accumulation response irrespective of light intensities, enhanced leaf photosynthesis, and increased plant biomass production. These findings underscore the importance of the chloroplast accumulation response in leaf photosynthesis and biomass production.