Development of marker-free transgenic <it>Jatropha </it>plants with increased levels of seed oleic acid

<p>Abstract</p> <p>Background</p> <p><it>Jatropha curcas </it>is recognized as a new energy crop due to the presence of the high amount of oil in its seeds that can be converted into biodiesel. The quality and performance of the biodiesel depends on the chemical composition of the fatty acids present in the oil. The fatty acids profile of the oil has a direct impact on ignition quality, heat of combustion and oxidative stability. An ideal biodiesel composition should have more monounsaturated fatty acids and less polyunsaturated acids. Jatropha seed oil contains 30% to 50% polyunsaturated fatty acids (mainly linoleic acid) which negatively impacts the oxidative stability and causes high rate of nitrogen oxides emission.</p> <p>Results</p> <p>The enzyme 1-acyl-2-oleoyl-sn-glycero-3-phosphocholine delta 12-desaturase (FAD2) is the key enzyme responsible for the production of linoleic acid in plants. We identified three putative <it>delta </it><it>12 </it><it>fatty acid desaturase </it>genes in <it>Jatropha </it>(<it>JcFAD2s</it>) through genome-wide analysis and downregulated the expression of one of these genes, <it>JcFAD2-1</it>, in a seed-specific manner by RNA interference technology. The resulting <it>JcFAD2-1 </it>RNA interference transgenic plants showed a dramatic increase of oleic acid (> 78%) and a corresponding reduction in polyunsaturated fatty acids (< 3%) in its seed oil. The control <it>Jatropha </it>had around 37% oleic acid and 41% polyunsaturated fatty acids. This indicates that FAD2-1 is the major enzyme responsible for converting oleic acid to linoleic acid in <it>Jatropha</it>. Due to the changes in the fatty acids profile, the oil of the <it>JcFAD2-1 </it>RNA interference seed was estimated to yield a cetane number as high as 60.2, which is similar to the required cetane number for conventional premium diesel fuels (60) in Europe. The presence of high seed oleic acid did not have a negative impact on other <it>Jatropha </it>agronomic traits based on our preliminary data of the original plants under greenhouse conditions. Further, we developed a marker-free system to generate the transgenic <it>Jatropha </it>that will help reduce public concerns for environmental issues surrounding genetically modified plants.</p> <p>Conclusion</p> <p>In this study we produced seed-specific <it>JcFAD2-1 </it>RNA interference transgenic <it>Jatropha </it>without a selectable marker. We successfully increased the proportion of oleic acid versus linoleic in <it>Jatropha </it>through genetic engineering, enhancing the quality of its oil.</p>