Second-strand cDNA priming is a central problem for full-length characterization of transcripts. A new strategy using bacteriophage T4 DNA ligase and partially degenerate adapters is proposed for grafting a sequence tag to the end of polyribonucleotides. Based on this RNA tagging system and previously described protocols, a new method for full-length cDNA production has been implemented. Validation of the method is shown in Arabidopsis thaliana by the construction of a full-length cDNA library and the analysis of 154 clones and by 5'-RACE-PCR run on a documented experimental system.