Light-induced chloroplast movements inOryzaspecies

Light-induced chloroplast movements control efficient light utilization in leaves, and thus, are essential for leaf photosynthesis and biomass production under fluctuating light conditions. Chloroplast movements have been intensively analyzed using wild-type and mutant plants ofArabidopsis thaliana. The molecular mechanism and the contribution to biomass production were elucidated. However, the knowledge of chloroplast movements is very scarce in other plant species, especially grass species including crop plants. Because chloroplast movements are efficient strategy to optimize light capture in leaves and thus promote leaf photosynthesis and biomass, analysis of chloroplast movements in crops is required for biomass production. Here, we analyzed chloroplast movements in a wide range of cultivated and wild species of genusOryza.All examinedOryzaspecies showed the blue-light-induced chloroplast movements. However,O. sativaand its ancestral speciesO. rufipogon, both of which are AA-genome species and usually grown in open condition where plants are exposed to full sunlight, showed the much weaker chloroplast movements thanOryzaspecies that are usually grown under shade or semi-shade conditions, includingO. officinalis,O. eichingeri, andO. granulata. Further detailed analyses of differentO. officinalisaccessions, including sun, semi-shade, and shade accessions, indicated that the difference in chloroplast movement strength between domesticated rice plants and wild species might result from the difference in habitat, and the shape of mesophyll chlorenchyma cells. The findings of this study provide useful information for optimizingOryzagrowth conditions, and lay the groundwork for improving growth and yield in staple food cropOryza sativa.