Targeted Growth, Inc., Suite 300, Seattle, WA 98102, USA.
BMC Plant Biol. 2010 Oct 27;10:233. doi: 10.1186/1471-2229-10-233.
Camelina sativa, 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 C. sativa genome, however. A study was undertaken to characterize two genes in the fatty acid biosynthesis pathway, fatty acid desaturase (FAD) 2 and fatty acid elongase (FAE) 1, which revealed unexpected complexity in the C. sativa genome.
In C. sativa, Southern analysis indicates the presence of three copies of both FAD2 and FAE1 as well as LFY, a known single copy gene in other species. All three copies of both CsFAD2 and CsFAE1 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 CsFAD2 and upstream of CsFAE1 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 C. sativa is approximately three-fold that of diploid Camelina relatives. Phylogenetic analyses further support a history of duplication and indicate that C. sativa and C. microcarpa might share a parental genome.
There is compelling evidence for triplication of the C. sativa genome, including a larger chromosome number and three-fold larger measured genome size than other Camelina relatives, three isolated copies of FAD2, FAE1, and the KCS17-FAE1 intergenic region, and three expressed haplotypes observed for six predicted single-copy genes. Based on these results, we propose that C. sativa 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 C. sativa should consider and, when possible take advantage of, the implications of polyploidy.
荠蓝，十字花科的一种油料作物，由于其在生物燃料应用方面的潜力而重新引起人们的兴趣。然而，人们对荠蓝基因组的性质知之甚少。本研究对脂肪酸生物合成途径中的两个基因（脂肪酸去饱和酶（FAD）2 和脂肪酸延长酶（FAE）1）进行了特征描述，结果揭示了荠蓝基因组的出人意料的复杂性。
在荠蓝中，Southern 分析表明，FAD2 和 FAE1 以及 LFY（其他物种的单一拷贝基因）都存在三个拷贝。三个 CsFAD2 和 CsFAE1 拷贝都在发育中的种子中表达，序列比对表明存在先前描述的保守位点，这表明两个基因的所有三个拷贝都可能具有功能。CsFAD2 下游和 CsFAE1 上游区域与拟南芥基因组具有共线性。此外，在 454 测序分析中观察到六个预测的单拷贝基因的三个表达单倍型，而流式细胞术的结果表明荠蓝的 DNA 含量大约是二倍体荠蓝亲缘种的三倍。系统发育分析进一步支持了复制的历史，并表明荠蓝和荠蓝微种可能共享一个亲本基因组。
有确凿的证据表明荠蓝基因组发生了三倍化，包括比其他荠蓝亲缘种更大的染色体数和三倍的基因组大小，FAD2、FAE1 和 KCS17-FAE1 基因间区的三个独立拷贝，以及六个预测的单拷贝基因中观察到的三个表达单倍型。基于这些结果，我们建议将荠蓝视为异源六倍体。脂肪酸合成途径基因的特征描述将允许对这种新兴生物燃料作物的油组成进行未来的操作；然而，油组成的靶向操作和荠蓝的一般发展应该考虑并在可能的情况下利用多倍体的影响。
