Generation of expressed sequence tags of random root cDNA clones of Brassica napus by single-run partial sequencing

Two hundred thirty-seven expressed sequence tags (ESTs) of Brassica napus were generated by single-run partial sequencing of 197 random root cDNA clones. A computer search of these root ESTs revealed that 21 ESTs show significant similarity to the protein-coding sequences in the existing data bases, including five stress- or defense-related genes and four clones related to the genes from other kingdoms. Northern blot analysis of the 10 data base-matched cDNA clones revealed that many of the clones are expressed most abundantly in root but less abundantly in other organs. However, two clones were highly root specific. The results show that generation of the root ESTs by partial sequencing of random cDNA clones along with the expression analysis is an efficient approach to isolate genes that are functional in plant root in a large scale. We also discuss the results of the examination of cDNA libraries and sequencing methods suitable for this approach.