Accumulation of medium-chain, saturated fatty acyl moieties in seed oils of transgenic Camelina sativa.

With its high seed oil content, the mustard family plant Camelina sativa has gained attention as a potential biofuel source. As a bioenergy crop, camelina has many advantages. It grows on marginal land with low demand for water and fertilizer, has a relatively short life cycle, and is stress tolerant. As most other crop seed oils, camelina seed triacylglycerols (TAGs) consist of mostly long, unsaturated fatty acyl moieties, which is not desirable for biofuel processing. In our efforts to produce shorter, saturated chain fatty acyl moieties in camelina seed oil for conversion to jet fuel, a 12:0-acyl-carrier thioesterase gene, UcFATB1, from California bay (Umbellularia californica Nutt.) was expressed in camelina seeds. Up to 40% of short chain laurate (C12:0) and myristate (C14:0) were present in TAGs of the seed oil of the transgenics. The total oil content and germination rate of the transgenic seeds were not affected. Analysis of positions of these two fatty acyl moieties in TAGs indicated that they were present at the sn-1 and sn-3 positions, but not sn-2, on the TAGs. Suppression of the camelina KASII genes by RNAi constructs led to higher accumulation of palmitate (C16:0), from 7.5% up to 28.5%, and further reduction of longer, unsaturated fatty acids in seed TAGs. Co-transformation of camelina with both constructs resulted in enhanced accumulation of all three medium-chain, saturated fatty acids in camelina seed oils. Our results show that a California bay gene can be successfully used to modify the oil composition in camelina seed and present a new biological alternative for jet fuel production

Fatty acid compositions (mol%) of seed lipids in UcFATB1-transgenic camelina and in the wild type.

<p>T2 mCherry positive seeds from 7 independent transgenic lines and wild type were analyzed by gas chromatography. Values are the means±SD from five biological replicates. nd: not detectable.</p

Fatty acid composition of TAGs and <i>sn</i>-2 MAG from <i>UcFATB1</i> transgenic camelina T₃ homozygous line 12 and California bay.

<p>Values are the means ± SD of three biological replicates with 50 seeds per rep. (nd: not detectable).</p

Transgene <i>UcFATB1</i> expression was detected in T₃ immature seeds.

<p>There is no <i>UcFATB1</i> transgene expression detected in Wt. The <i>UcFATB1</i> expression level of Line 80 was used as a calibrator (expression level was arbitrarily set at 1), other lines’ expression levels were expressed as the fold of the expression level of line 80.</p

Medium-chain, saturated FA compositions in seed oil of two camelina lines co-transformed with <i>UcFATB1</i> and <i>CsKASII</i> RNAi-2.

<p>Thirty T₂ seeds of Line 15, and 26 seeds of Line 18, and four wild type seeds were analyzed by gas chromatography.</p

Seed oil content analysis of four T₄ <i>UcFATB1</i> transgenic lines and WT as measured with gas chromatography (30 mCherry positive or WT seeds per sample, 5 replicates).

<p>* indicates significant difference compared to other samples (P<0.05).</p

Fatty acid compositions of T₃ mCherry positive seeds from <i>CsKASII RNAi1</i> and <i>CsKASII RNAi2</i> transgenic lines.

<p>Each value is the mean ± SD of five biological replicates, six seeds per rep.</p

Accumulation of medium-chain, saturated fatty acyl moieties in seed oils of transgenic <i>Camelina sativa</i>

<div><p>With its high seed oil content, the mustard family plant <i>Camelina sativa</i> has gained attention as a potential biofuel source. As a bioenergy crop, camelina has many advantages. It grows on marginal land with low demand for water and fertilizer, has a relatively short life cycle, and is stress tolerant. As most other crop seed oils, camelina seed triacylglycerols (TAGs) consist of mostly long, unsaturated fatty acyl moieties, which is not desirable for biofuel processing. In our efforts to produce shorter, saturated chain fatty acyl moieties in camelina seed oil for conversion to jet fuel, a 12:0-acyl-carrier thioesterase gene, <i>UcFATB1</i>, from California bay (<i>Umbellularia californica</i> Nutt.) was expressed in camelina seeds. Up to 40% of short chain laurate (C12:0) and myristate (C14:0) were present in TAGs of the seed oil of the transgenics. The total oil content and germination rate of the transgenic seeds were not affected. Analysis of positions of these two fatty acyl moieties in TAGs indicated that they were present at the <i>sn-1</i> and <i>sn-3</i> positions, but not <i>sn-2</i>, on the TAGs. Suppression of the camelina <i>KASII</i> genes by RNAi constructs led to higher accumulation of palmitate (C16:0), from 7.5% up to 28.5%, and further reduction of longer, unsaturated fatty acids in seed TAGs. Co-transformation of camelina with both constructs resulted in enhanced accumulation of all three medium-chain, saturated fatty acids in camelina seed oils. Our results show that a California bay gene can be successfully used to modify the oil composition in camelina seed and present a new biological alternative for jet fuel production.</p></div

Algal ancestor of land plants was preadapted for symbiosis

Colonization of land by plants was a major transition on Earth, but the developmental and genetic innovations required for this transition remain unknown. Physiological studies and the fossil record strongly suggest that the ability of the first land plants to form symbiotic associations with beneficial fungi was one of these critical innovations. In angiosperms, genes required for the perception and transduction of diffusible fungal signals for root colonization and for nutrient exchange have been characterized. However, the origin of these genes and their potential correlation with land colonization remain elusive. A comprehensive phylogenetic analysis of 259 transcriptomes and 10 green algal and basal land plant genomes, coupled with the characterization of the evolutionary path leading to the appearance of a key regulator, a calcium- and calmodulin-dependent protein kinase, showed that the symbiotic signaling pathway predated the first land plants. In contrast, downstream genes required for root colonization and their specific expression pattern probably appeared subsequent to the colonization of land. We conclude that the most recent common ancestor of extant land plants and green algae was preadapted for symbiotic associations. Subsequent improvement of this precursor stage in early land plants through rounds of gene duplication led to the acquisition of additional pathways and the ability to form a fully functional arbuscular mycorrhizal symbiosis