Preliminary analysis on the role of an EF-hand binding protein gene TaCab1 in wheat leaves challenged with Puccinia striiformis f. sp. tritici Silencing of Chalcone Synthase Genes by Artificial microRNA in Petunia The Potential Application of microRNA-mediated Gene Regulation in Crop Improvement Silencing of Chalcone Synthase Genes by Artificial microRNA in Petunia Construction of Artificial miRNA of ptc-miR213 Expression Vector and Transformation into Arabidopsis thaliana