Cold-specific and light-stimulated expression of a wheat (Triticum aestivum L.) Cor gene Wcor15 encoding a chloroplast-targeted protein

Wcor15, a member of the wheat cold-responsive (Cor) gene family, has been isolated and characterized. The deduced polypeptide WCOR15 (MW=14.7 kDa) showed high homology to the previously identified wheat and barley COR proteins. Southern blot analysis using diploid, tetraploid and hexaploid wheat and diploid Aegilops species showed that the wheat and related wild genomes possessed multiple copies of Wcor15 homologues. Five copies were assigned to the homoeologous group 2 chromosomes by nulli-tetrasomic analysis. Northern blot analysis showed that expression of Wcor15 was specifically induced by low-temperature. Homologous transcripts accumulated in leaves, and light markedly increased their steady-state levels. Bombardment-mediated transient expression analysis of a chimeric CaMV 35S::Wcor15-GFP construct showed protein-targeting to epidermal guard cell chloroplasts in excised spiderwort leaves. A promoter of Wcor15 contained at least three CRT/DRE-like sequence motifs found in Arabidopsis Cor genes and induced the reporter GUS gene expression in leaves of transgenic tobacco plants under low-temperature and light conditions. These results suggest that the functional Cor gene system involving the CRT/DRE cis-element is conserved in both monocotyledonous and dicotyledonous plants.