Integrative transcriptomic and HPTL-ESI-MS analysis reveals a strong coordination between genes and pathways contributing to high erucic triacylglycerol biosynthesis during Pennycress (Thlaspi arvense L.) seed maturation

Abstract

Thlaspi arvense (Pennycress) is an emerging feedstock for biofuel production because of its high seed-oil content enriched in erucic acid (35-40% of total fatty acids). A transcriptomic analysis together with an HPTLC-ESI-MS and MSn positional analysis characterization of the TAG fractions in five different seed maturation stages was performed to study the high erucic seed-oil biosynthesis in Pennycress. The RNA-Seq data showed a temporal pattern of regulation in which genes involved in the synthesis of carbon precursors and fatty acids were highly abundant at the earlier stages of maturation, then decreasing in the mature ones. Genes involved in TAG biosynthesis showed a complex temporal regulation in which DGAT2 and PDAT1 showed higher expression at the earlier stages of maturation, coincident with the rapid incorporation of 22:1 to TAG. Genes from the acyl-editing pathway showed higher expression at the earlier stages of seed maturation, suggesting a major role of this pathway at the initial stages of seed-oil biosynthesis. HPTLC-ESI-MS analysis showed an increase of TAG species containing VLCFAs (22:1 and 24:1) with 18:2 at sn-2 position with seed maturation. This increase was concomitant with an increase of DGAT1 and PDAT2 mRNA levels, suggesting a higher Kennedy pathway activity. However, the concerted regulation between DGAT and PDAT enzymes suggested a coordination between pathways, isoforms and substrate pools for the synthesis of high erucic TAG in Pennycress.