Efficient Genetic Transformation of Jatropha Curcas L. by Means of Vacuum Infiltration Combined with Filter-Paper Wicks

Jatropha curcas L. (Jatropha) is a promising plant for the production of biodiesel in arid regions. To improve its productivity, it is important to understand the molecular functions of key genes in Jatropha, and to seek ways to modify important agronomic traits of Jatropha via molecular breeding. However, Jatropha is notorious for its recalcitrance to transformation. Thus, an improved protocol for efficient and reproducible Agrobacterium tumefaciens-mediated transformation is essential for molecular biology research and breeding in this species. Because resistance of Jatropha to A. tumefaciens infection is one of the key factors limiting transformation efficiency, we attempted to improve infection efficiency by comparing various co-culture conditions with the use of a β-glucuronidase (GUS) assay. The LBA4404 strain of A. tumefaciens was more efficient than the EHA105 strain for transformation of Jatropha. Vacuum infiltration of an A. tumefaciens suspension with Jatropha explants, combined with co-cultivation on filter-paper wicks moistened with co-culture medium instead of on solid medium, significantly improved transformation efficiency. In these conditions, GUS-positive sectors were observed in 93.0 ± 23.6% of infected explants. Moreover, a variant of the yellow fluorescent protein gene, Venus, was used as a visible marker, which proved effective for discrimination of candidate transgenic shoots from escape shoots. Transgene integration was confirmed by means of polymerase chain reaction and Southern hybridization analyses. Transgenic shoots were regenerated from 23% of explants from the vacuum-filter-paper treatment, which is sufficient for practical use.