SUMMARY
Improvement of drought tolerance in plants depends upon understanding their molecular responses to dehydration stress. The drought resistance of 14 varieties of tall fescue (Festuca arundinacea Schreb.) was analysed by measuring various physiological traits under high temperature and drought conditions. A dehydration-responsive elementbinding-2 (DREB2) homologue cDNA from the cultivar ‘Plantation’, with high drought tolerance, designated FapDREB2, was isolated and sequenced.The FapDREB2 cDNA was predicted to encode a protein of 262 amino acid residues, with a molecular mass of 41.3 kDa and a pI of 5.28. Its deduced protein sequence, with a conserved AP2 DNA-binding domain, shared characteristics with the DREB2 gene family based on sequence homology, structure and phylogenetic analysis. Expression of the FapDREB2 gene in different plant organs indicated that its transcripts were abundant in leaves and leaf sheaths, and scarce in roots. In addition, FapDREB2 gene expression under drought and high temperature conditions was stronger than without such treatments in the laboratory. FapDREB2 mRNA
accumulated in response to various abiotic stresses, confirming that its expression was induced more prominently by drought or salt treatment than by cold stress, and did not respond to abscisic acid (ABA) treatment. FapDREB2 gene expression in seedlings grown in a study plot varied irregularly under drought and high temperature conditions, in contrast to seedlings grown with drought treatment in the laboratory. This suggests that expression of the DREB2 transcription factor would be complex during plant responses to different stresses.We concluded that the FapDREB2 gene is involved in plant responses to drought or salt stress through an ABA-independent pathway, which may lead to a better understanding of the regulatory mechanism of the DREB2 transcription factor in tall fescue.