Sucrose-induced changes in the transcriptome of cell suspension cultures of oilseed rape reveal genes associated with lipid biosynthesis

Abstract

Microspore-derived cell suspension cultures of Brassica napus L. cv Jet Neuf grown in increasing concentrations of sucrose have been shown to produce increasing amounts of triacylglycerol (TAG) that are accompanied by increasing acyl-CoA:diacylglycerol acyltransferase (DGAT; EC 2.3.1.20) activity. Here, we show that the sucrose-induced increase in the TAG biosynthetic capacity of these cells is also associated with increased production of mRNA encoding DGAT. In addition, differential display (DD) of mRNA was used to evaluate the production of other transcripts that might be linked to lipid biosynthesis that were induced by increasing the sucrose concentration in the growth media. The PCR-based technique identified eight cDNA fragments representing upregulated transcripts. The deduced amino acid sequence of one of these fragments displayed 96% identity to a mitochondrial acyl carrier protein from Arabidopsis thaliana suggesting a possible association between fatty acid biosynthesis in the mitochondria and TAG biosynthesis in the endoplasmic reticulum. Two other cDNA fragments encoded polypeptide segments that exhibited a high level of identity to ethylene-inducible protein and a member of the thioredoxin superfamily from A. thaliana. Another cDNA fragment had homology to sequences of unknown function whereas the remaining five cDNA fragments had no homology to previously reported sequences, and therefore represented the expression of unknown genes. Collectively, these results suggest DD of mRNA was an effective method for monitoring sucrose-modulated gene expression and that the method has the potential to identify novel sequences that may be related directly or indirectly to plant lipid metabolism.