Abstract
The chloroplast is not only the site of photosynthesis but also performs biosynthesis of amino acids, lipid and phytohormones. Because of its endosymbiotic origin, chloroplasts proliferate by division. Recent studies in Arabidopsis mutants such as arc have revealed important molecular components involved in chloroplast division. Generally, mutants defective in chloroplast division machinery have enlarged chloroplasts. However, many of these mutants exhibit normal growth and the biological significance of chloroplast division remains unclear. To examine this question, we attempt to isolate rice mutants that have large chloroplasts. We screened an EMS-mutagenized M1 population of a Nipponbare line derived from tissue culture and showing coarse grain yield. Because chloroplasts were difficult to observe in intact rice leaves unlike Arabidopsis, protoplasts were prepared from third leaves of each plant. Overall, we screened 2,170 samples from 162 independent M1 lines by this method and isolated one line that had enlarged chloroplasts and was termed gic. This mutant so far grows normally and its phenotypic characterization will be presented.
