An Analysis of Molecular Structural Character and Function Prediction on 1-deoxy-D-xylulose-5-phosphate Reductoisomerase, a Key Enzyme in Plant Isoprenoid Biosynthesis Identification of 1-deoxy-D-xylulose-5-phosphate synthase and analysis on essential oil in Magnolia officinalis Cloning and expression analysis of 1-deoxy-D-xylulose-5-phosphate synthase 1 gene in Houttuynia cordata Cloning and differential expression of 1-deoxy-D-xylulose-5-phosphate reductoisomerase gene in Houttuynia cordata