Identification of Differentially Expressed Genes in Brassinosteroid-Treated 'Brassica napus' Seedlings

Brassinosteroid-mediated gene expression changes have been reported primarily in 'Arabidopsis thaliana' but not in its close relative Brassica napus. To obtain an initial idea of the molecular changes induced by long-term exposure to 24-epibrassinolide (EBR) in 'B. napus' seedlings, we used the differential display-reverse transcription PCR technique. Six differentially expressed cDNAs were isolated and characterized. These encode a mitochondrial transcription termination factor (mTERF)-related protein, glycine-rich protein 22 (GRP22), myrosinase, 3-ketoacyl-CoA thiolase, and a copia-like polyprotein. The first four were upregulated in EBR-treated seedlings while the latter was expressed at higher levels in untreated seedlings. Transcripts of mTERF-related protein, GRP22, and myrosinase were present at higher levels in treated seedlings under nonstress conditions, whereas those of 3-ketoacyl-CoA thiolase rose to higher levels in treated seedlings during exposure to heat stress. The results of the present study indicate that EBR treatment in 'B. napus' leads to substantial changes in the expression levels of genes involved in a variety of physiologic responses. The results provide a useful framework for further research into EBR-mediated molecular changes in 'B. napus', which will also add to our understanding of how brassinosteroids mediate stress tolerance in this agriculturally important oil crop.