Beschreibung:
<jats:title>Summary</jats:title><jats:p>Constitutive over‐expression of the <jats:styled-content style="fixed-case"><jats:italic>TaDREB3</jats:italic></jats:styled-content> gene in barley improved frost tolerance of transgenic plants at the vegetative stage of plant development, but leads to stunted phenotypes and 3‐ to 6‐week delays in flowering compared to control plants. In this work, two cold‐inducible promoters with contrasting properties, the <jats:italic><jats:styled-content style="fixed-case">WRKY</jats:styled-content>71</jats:italic> gene promoter from rice and the <jats:italic><jats:styled-content style="fixed-case">C</jats:styled-content>or39</jats:italic> gene promoter from durum wheat, were applied to optimize expression of <jats:styled-content style="fixed-case"><jats:italic>TaDREB3</jats:italic></jats:styled-content>. The aim of the work was to increase plant frost tolerance and to decrease or prevent negative developmental phenotypes observed during constitutive expression of <jats:styled-content style="fixed-case"><jats:italic>TaDREB3</jats:italic></jats:styled-content>. The <jats:italic><jats:styled-content style="fixed-case">OsWRKY71</jats:styled-content></jats:italic> and <jats:italic><jats:styled-content style="fixed-case">TdCor39</jats:styled-content></jats:italic> promoters had low‐to‐moderate basal activity and were activated by cold treatment in leaves, stems and developing spikes of transgenic barley and rice. Expression of the <jats:styled-content style="fixed-case"><jats:italic>TaDREB3</jats:italic></jats:styled-content> gene, driven by either of the tested promoters, led to a significant improvement in frost tolerance. The presence of the functional <jats:styled-content style="fixed-case">TaDREB3</jats:styled-content> protein in transgenic plants was confirmed by the detection of strong up‐regulation of cold‐responsive target genes. The <jats:italic><jats:styled-content style="fixed-case">OsWRKY71</jats:styled-content></jats:italic> promoter–driven <jats:styled-content style="fixed-case"><jats:italic>TaDREB3</jats:italic></jats:styled-content> provides stronger activation of the same target genes than the <jats:italic><jats:styled-content style="fixed-case">TdCor39</jats:styled-content></jats:italic> promoter. Analysis of the development of transgenic plants in the absence of stress revealed small or no differences in plant characteristics and grain yield compared with wild‐type plants. The <jats:italic>WRKY71–</jats:italic><jats:styled-content style="fixed-case"><jats:italic>TaDREB3</jats:italic></jats:styled-content> promoter–transgene combination appears to be a promising tool for the enhancement of cold and frost tolerance in crop plants but field evaluation will be needed to confirm that negative development phenotypes have been controlled.</jats:p>