Abstract:

A cDNA clone encoding DREB2Awas isolated from a cDNA library prepared under drought stress by the gene-specific PCR amplification from Populus tomentosa. The cDNA was 946 bp in length with an open reading frame (ORF, 864 bp in length) which is capable of encoding a protein of 287 amino acids. The deduced protein sequence of the PtDREB2A shares 80.3％, and 83.3％ identity with functional domain of AP2/ERF of Arabidopsis thaliana AtDREB2A, and Oryza sativa OsDREB2A, respectively. Tissue differential expression detected with realtime-PCR indicated that PtDREB2Atranscripts had their mRNA products in roots, stems, leaves and apical shoot meristems with varied levels. The PtDREB 2Atranscripts were the most abundant mRNA products in leaves, with medium expression in stem bark and roots, but a weak expression was detected in apical shoot meristems, and in the phloem, cambium, and xylem of stem. We analyzed the expression patterns of PtDREB2Aunder abiotic stress conditions and phytohormone treatment, and revealed that expression of PtDREB2A was induced by heat-shock, cold, drought and high-salt stress, but also by IAA, NAA, and GA₃, not by ABA. The genomic sequences of PtDREB2A in 45 individuals were aligned, compared and analyzed using the software MEGA4.0 and DnaSP4.50.4. A total of 49 single nucleotide polymorphisms (SNPs) were detected and the frequency and diversity of SNPs were 1/18 bp and 0.010 48, respectively. In total, 46 SNPs were detected in the coding regions of PtDREB2A, of which 19 and 27 were silent and missense mutations, respectively. The results, therefore, would provide the important foundation for gene-assisted improvement of tolerance to abiotic stresses in P. tomentosa.

Key words: Populus tomentosa, DREB2A gene, abiotic stress, single nucleotide polymorphisms