Polyploid genome of Camelina sativa revealed by isolation of fatty acid synthesis genes

<p>Abstract</p> <p>Background</p> <p><it>Camelina sativa</it>, an oilseed crop in the Brassicaceae family, has inspired renewed interest due to its potential for biofuels applications. Little is understood of the nature of the <it>C. sativa </it>genome, however. A study was undertaken to characterize two genes in the fatty acid biosynthesis pathway, <it>fatty acid desaturase (FAD) 2 </it>and <it>fatty acid elongase (FAE) 1</it>, which revealed unexpected complexity in the <it>C. sativa </it>genome.</p> <p>Results</p> <p>In <it>C. sativa</it>, Southern analysis indicates the presence of three copies of both <it>FAD2 </it>and <it>FAE1 </it>as well as <it>LFY</it>, a known single copy gene in other species. All three copies of both <it>CsFAD2 </it>and <it>CsFAE1 </it>are expressed in developing seeds, and sequence alignments show that previously described conserved sites are present, suggesting that all three copies of both genes could be functional. The regions downstream of <it>CsFAD2 </it>and upstream of <it>CsFAE1 </it>demonstrate co-linearity with the Arabidopsis genome. In addition, three expressed haplotypes were observed for six predicted single-copy genes in 454 sequencing analysis and results from flow cytometry indicate that the DNA content of <it>C. sativa </it>is approximately three-fold that of diploid <it>Camelina </it>relatives. Phylogenetic analyses further support a history of duplication and indicate that <it>C. sativa </it>and <it>C. microcarpa </it>might share a parental genome.</p> <p>Conclusions</p> <p>There is compelling evidence for triplication of the <it>C. sativa </it>genome, including a larger chromosome number and three-fold larger measured genome size than other <it>Camelina </it>relatives, three isolated copies of <it>FAD2</it>, <it>FAE1</it>, and the <it>KCS17-FAE1 </it>intergenic region, and three expressed haplotypes observed for six predicted single-copy genes. Based on these results, we propose that <it>C. sativa </it>be considered an allohexaploid. The characterization of fatty acid synthesis pathway genes will allow for the future manipulation of oil composition of this emerging biofuel crop; however, targeted manipulations of oil composition and general development of <it>C. sativa </it>should consider and, when possible take advantage of, the implications of polyploidy.</p

Engineering Vitamin E Content: From Arabidopsis Mutant to Soy Oil

We report the identification and biotechnological utility of a plant gene encoding the tocopherol (vitamin E) biosynthetic enzyme 2-methyl-6-phytylbenzoquinol methyltransferase. This gene was identified by map-based cloning of the Arabidopsis mutation vitamin E pathway gene3-1 (vte3-1), which causes increased accumulation of δ-tocopherol and decreased γ-tocopherol in the seed. Enzyme assays of recombinant protein supported the hypothesis that At-VTE3 encodes a 2-methyl-6-phytylbenzoquinol methyltransferase. Seed-specific expression of At-VTE3 in transgenic soybean reduced seed δ-tocopherol from 20 to 2%. These results confirm that At-VTE3 protein catalyzes the methylation of 2-methyl-6-phytylbenzoquinol in planta and show the utility of this gene in altering soybean tocopherol composition. When At-VTE3 was coexpressed with At-VTE4 (γ-tocopherol methyltransferase) in soybean, the seed accumulated to >95% α-tocopherol, a dramatic change from the normal 10%, resulting in a greater than eightfold increase of α-tocopherol and an up to fivefold increase in seed vitamin E activity. These findings demonstrate the utility of a gene identified in Arabidopsis to alter the tocopherol composition of commercial seed oils, a result with both nutritional and food quality implications

Distinct Prion Domain Sequences Ensure Efficient Amyloid Propagation by Promoting Chaperone Binding or Processing <i>In Vivo</i>

<div><p>Prions are a group of proteins that can adopt a spectrum of metastable conformations <i>in vivo</i>. These alternative states change protein function and are self-replicating and transmissible, creating protein-based elements of inheritance and infectivity. Prion conformational flexibility is encoded in the amino acid composition and sequence of the protein, which dictate its ability not only to form an ordered aggregate known as amyloid but also to maintain and transmit this structure <i>in vivo</i>. But, while we can effectively predict amyloid propensity <i>in vitro</i>, the mechanism by which sequence elements promote prion propagation <i>in vivo</i> remains unclear. In yeast, propagation of the [<i>PSI</i>^<i>+</i>] prion, the amyloid form of the Sup35 protein, has been linked to an oligopeptide repeat region of the protein. Here, we demonstrate that this region is composed of separable functional elements, the repeats themselves and a repeat proximal region, which are both required for efficient prion propagation. Changes in the numbers of these elements do not alter the physical properties of Sup35 amyloid, but their presence promotes amyloid fragmentation, and therefore maintenance, by molecular chaperones. Rather than acting redundantly, our observations suggest that these sequence elements make complementary contributions to prion propagation, with the repeat proximal region promoting chaperone binding to and the repeats promoting chaperone processing of Sup35 amyloid.</p></div