Expression of storage lipid biosynthesis transcription factors and enzymes in Jatropha curcas L. cell suspension cultures and seeds

Abstract

The oleaginous Jatropha curcas has been proposed as a promising source for biodiesel production in seed or potentially by in vitro production in cell cultures. However, little is known concerning the optimal growth conditions and the transcription of key factors and enzymes involved in the biosynthesis of storage lipids in J. curcas cell cultures. Additional knowledge is also needed for these factors in seeds. Here, we assess target gene expression in endosperm cells in planta and endosperm-derived cell suspension cultures (EDCCs). Endosperm cells were taken from three representative seed developmental stages, and cell suspensions were grown from these samples. Glucose, nitrogen, and abscisic acid concentrations were varied in an attempt to optimize biomass growth and oil yield. Oil production in EDCCs reached a maximum of 5% (w/w) of total lipids. Although much lower than lipid production in seed, lipid profiles of EDCCs remain identical to those produced in planta. The expression levels of five major transcription factors (TFs), as well as KAS1, accA, DGAT1/2 and PDAT1 enzymes, and the OLE1 protein, all key components of the lipid biosynthesis pathway were also measured. Significant expression of LEC1, FUS3, ABI3, and WRI1 was found in endosperm cells throughout seed development, suggesting similar functions to their counterparts in Arabidopsis and providing a reference expression level for cell cultures. J. curcas EDCCs showed lower expression of most TFs compared with endosperm tissue, with the exception of WRI1 which had comparable expression levels in the two systems. Conversely, the enzymes KAS1, accA, and DGAT had the same or higher expression levels in EDCCs versus endosperm cells. Interestingly, the genes that encoded for DGAT1 and DGAT2 enzymes were found preferentially expressed in endosperm cells and EDCCs, respectively. Contrary to other studies, our findings indicate that the addition of ABA does not result in increased expression of genes involved in storage lipid biosynthesis.