This invention relates to an isolated nucleic acid fragment encoding a 1-deoxy-D-xylulose 5-phosphate reductoisomerase. The invention also relates to the construction of a chimeric gene encoding all or a portion of the 1-deoxy-D-xylulose 5-phosphate reductoisomerase, in sense or antisense orientation, wherein expression of the chimeric gene results in production of altered levels of the 1-deoxy-D-xylulose 5-phosphate reductoisomerase in a transformed host cell.