Comparative study of screening with subtracted probe and differential screening on isolation of flower-specific cDNA clones from Nicotiana sylvestris

A simple and efficient screening procedure for isolation of tissue-specific cDNA clones is described. A plasmid cDNA library was constructed from mRNAs extracted from Nicotiana sylvestris flower buds. Flower-specific cDNA clones were identified after screening of the cDNA library with subtracted probe enriched for flower-specific sequences. Comparison of this procedure with the conventional differential screening indicated that it has the advantages of direct isolation of highly specific cDNA clones, as well as identification of less abundant specifically expressed clones. The isolated cDNA clones were classified into 14 independent cross-hybridization groups, Northern blot analysis with the cDNA clones as probes, distinguished three types of mRNA expression patterns: (1) specific expression in stamen during a restricted period of flower development; (2) expression in the reproductive organs; (3) expression in both the structural and reproductive flower organs, Sequencing revealed that 6 of the groups correspond to known genes, but the remaining 8 were not homologous to the sequences in the data bank.