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


RESULTS
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.


CONCLUSIONS
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.
Hutcheon
Carolyn
C
Targeted Growth, Inc., Suite 300, Seattle, WA 98102, USA. jay.derocher@targetedgrowth.com
Ditt
Renata F
RF
Beilstein
Mark
M
Comai
Luca
L
Schroeder
Jesara
J
Goldstein
Elianna
E
Shewmaker
Christine K
CK
Nguyen
Thu
T
De Rocher
Jay
J
Kiser
Jack
J
D000123:Acetyltransferases / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D001483:Base Sequence; D019607:Brassicaceae / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D044943:Fatty Acid Desaturases / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D000081031:Fatty Acid Elongases; D005227:Fatty Acids / Q000096:biosynthesis; D018628:Gene Dosage; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D018745:Genome, Plant / Q000235:genetics; D008969:Molecular Sequence Data; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D020641:Polymorphism, Single Nucleotide; D011123:Polyploidy; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid
D005227:Fatty Acids; D010940:Plant Proteins; D044943:Fatty Acid Desaturases; C040448:delta-12 fatty acid desaturase; D000123:Acetyltransferases; D000081031:Fatty Acid Elongases