We studied erucic acid accumulation in the biodiesel feedstock Pennycress (Thlaspi arvense L.) as a first step towards the development of a sustainable strategy for biofuel production in the EU territory. To that end, two inbred Pennycress lines of European origin, "NASC" and "French," were cultivated in a controlled chamber and in experimental field plots, and their growth, seed production and seed oil characteristics analyzed. Differences in some agronomical traits like vernalization (winter-French versus spring-NASC), flowering time (delayed in the French line) and seed production (higher in the French line) were detected. Both lines showed a high amount (35-39%) of erucic acid (22:1) in their seed oil. Biochemical characterization of the Pennycress seed oil indicated that TAG was the major reservoir of 22:1. Incorporation of 22:1 to TAG occurred very early during seed maturation, concomitant with a decrease of desaturase activity. This change in the acyl fluxes towards elongation was controlled by different genes at different levels. TaFAE1 gene, encoding the fatty acid elongase, seemed to be controlled at the transcriptional level with high expression at the early stages of seed development. On the contrary, the TaFAD2 gene that encodes the Δ12 fatty acid desaturase or TaDGAT1 that catalyzes TAG biosynthesis were controlled post-transcriptionally. TaWRI1, the master regulator of seed-oil biosynthesis, showed also high expression at the early stages of seed development. Our data identified genes and processes that might improve the biotechnological manipulation of Pennycress seeds for high-quality biodiesel production.

Melon Fusarium wilt (MFW), caused by Fusarium oxysporum f. sp. melonis (Fom), is one of the most destructive diseases of melon (Cucumis melo L.). The development and deployment of resistant cultivars is generally considered to be the best approach to control MFW. Based on the host resistance genes associated with variants of this pathogen, Fom isolates were classified into four physiological races designated 0, 1, 2, and 1,2. Two dominant resistance genes, Fom-1 and Fom-2, control resistance to races 0 and 2, and 0 and 1, respectively. Fom isolates classified as race 1,2 are able to induce disease in melon lines carrying the above resistance genes. Many sources of resistance to Fom races 0, 1, and 2 have been reported. Partial resistance to race 1,2 controlled by polygenic recessive genes was only detected in a few Far Eastern melon accessions, except for the breeding line BIZ where complete resistance was described. Identification of DNA markers tightly linked to genes conferring resistance to Fom has immediate application in MFW resistance breeding programs. The Fom-2 gene has been cloned, and it encodes a protein with a nucleotide binding site (NBS) and leucine-rich repeats domain (LRR). Based on the sequence of this domain, some molecular markers linked to this gene were developed. Several DNA markers linked to Fom-1 have also been described. However, the usefulness of these markers was variety-dependent. Therefore, their combined use would be very useful in marker assisted selection for introducing resistance to Fom races 0 and 2 in melon. Recently, these markers were used for the positional cloning of this gene, which encoded a protein with a NBS–LRR domains that shows similarity to the toll and interleukin-1 receptores (TIR). Regarding Fom race 1,2, nine QTL were detected on five linkage groups by composite interval mapping. In this paper we review the current knowledge of MFW disease, and focus on genetic resistance to Fom and marker-assisted selection for resistance.

Brassicaceae present a great heterogeneity of seed oil and fatty acid composition, accumulating Very Long Chain Fatty Acids with industrial applications. However, the molecular determinants of these differences remain elusive. We have studied the βketoacyl-CoA synthase from the high erucic feedstock Thlaspi arvense (Pennycress).Functional characterization of the Pennycress FAE1 enzyme was performed in two Arabidopsis backgrounds; Col-0, with less than 2.5% of erucic acid in its seed oil and the fae1-1 mutant, deficient in FAE1 activity, that did not accumulate erucic acid. Seedspecific expression of the Pennycress FAE1 gene in Col-0 resulted in a 3 to 4-fold increase of erucic acid content in the seed oil. This increase was concomitant with a decrease of eicosenoic acid levels without changes in oleic ones. Interestingly, only small changes in eicosenoic and erucic acid levels occurred when the Pennycress FAE1 gene was expressed in the fae1-1 mutant, with high levels of oleic acid available for elongation, suggesting that the Pennycress FAE1 enzyme showed higher affinity for eicosenoic acid substrates, than for oleic ones in Arabidopsis. Erucic acid was incorporated to triacylglycerol in the transgenic lines without significant changes in their levels in the diacylglycerol fraction, suggesting that erucic acid was preferentially incorporated to triacylglycerol via DGAT1. Expression analysis of FAE1, AtDGAT1, AtLPCAT1 and AtPDAT1 genes in the transgenic lines further supported this conclusion. Differences in FAE1 affinity for the oleic and eicosenoic substrates among Brassicaceae, as well as their incorporation to triacylglycerol might explain the differences in composition of their seed oil.

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