SRA

Transcriptome analysis based on deep EST sequencing allows quantitative comparisons of gene expression across multiple species. Using pyrosequencing, we generated over seven million ESTs from four stages of developing seeds of Ricinus communis, Brassica napus, Euonymus alatus and Tropaeolum majus, which differ in their storage tissue for oil, ability to photosynthesize and in the structure and content of triacylglycerols (TAG). The larger number of ESTs in these 16 datasets provided reliable estimates of the expression of acyltransferases and other enzymes expressed at low levels. Analysis of EST levels from these oilseeds revealed both conserved and distinct species-specific expression patterns for genes involved in synthesis of glycerolipids and their precursors. Independent of the species and tissue type, ESTs for core fatty acid synthesis enzymes maintained a conserved stoichiometry and a strong correlation in temporal profiles throughout seed development. However, ESTs associated with non-plastid enzymes of oil biosynthesis displayed dissimilar temporal patterns indicative of different regulation. The EST levels for several genes potentially involved in accumulation of unusual TAG structures were distinct. Comparison of expression of members from multi-gene families allowed identification of specific isoforms with conserved function in oil biosynthesis. In all four oilseeds, ESTs for RuBisCo were present suggesting its possible role in carbon metabolism, irrespective of light availability. Together, these data provide a resource for the scientific community for comparative and functional genomics of diverse oilseeds. Expression data for >350 genes encoding enzymes and proteins involved in lipid metabolism are available at the 'ARALIP' website (http://aralip.plantbiology.msu.edu/)*.