Search

It was recently shown that allopolyploidy brings novel epistatic interactions to genes belonging to different genomes. However, systematic studies of the phenotypic relationships between synthetic hexaploid wheats and their parental lines have not been conducted. In this study, 27 synthetic hexaploid wheats were produced by crossing the tetraploid wheat cultivar ‘Langdon’ with 27 accessions of Aegilops tauschii. Variations in 20 morphological and flowering traits were analysed in both the synthetic wheat lines and the parental Ae. tauschii accessions. The 20 traits exhibited large variations in the wheat lines. For many of the traits, the degree of variation in the parental accessions was reduced in the hexaploid derivatives. Principal component analysis of floret-related traits divided the Ae. tauschii accessions into two subspecies, ssp. tauschii and ssp. strangulata, but this parental pattern of subspecific division was not detectable in the hexaploids. Our results suggest that the ‘Langdon’ genome may have an alleviating effect on the expression of D-genome-derived variations in derived synthetics. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM PUBLISHER]

Time‐courses of the development of freezing tolerance and the expression of a cold‐responsive gene wlt10 were monitored during cold acclimation in wheat (Triticum aestivum L.). Bioassay showed that cold acclimation conferred much higher freezing tolerance on a winter cultivar than a spring cultivar. Northern blot analysis showed that the expression of wlt10 encoding a novel wheat member of a cereal‐specific LT‐COR protein family was specifically induced by low temperature. A freezing‐tolerant winter cultivar accumulated the mRNA more rapidly and for a longer period than a susceptible spring cultivar. The increase in the amount of mRNA was temporary but the peak occurred at the time when the maximum level of freezing tolerance was attained. The mRNA accumulated more in the leaves than in the roots, and different light/dark regimes modulated the level of mRNA accumulation. Genomic Southern blot analyses using the nulli‐tetrasomic series showed that the wlt10 homologues were located on the homologous group 2 chromosomes. [ABSTRACT FROM PUBLISHER]