Compositions and methods include genetically encoding and expressing a novel &Dgr;9-18:0-ACP desaturase in plant cells. In some embodiments, nucleic acid molecules encode the novel &Dgr;9-18:0-ACP desaturase. In other embodiments, amino acid sequences have &Dgr;9-18:0-ACP desaturase activity. Methods can involve expression of &Dgr;9-18:0-ACP desaturase in plant cells, plant materials, and whole plants for the purpose of increasing the amount of unusual fatty acids in whole plants, plant seeds, and plant materials, for example, seeds.MOLÉCULA DE ACIDO NUCLEICO QUE CODIFICA UNA ENZIMA ?9 DESATURASA, Y MÉTODO PARA INCREMENTAR CANTIDAD DE ÁCIDOS GRASOS INSATURADOS EN PLANTAS.