Cellular and molecular basis of low temperature tolerance in cereals

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Winter cereals require prolonged exposure to low temperature (LT) to trigger the genetic mechanisms to induce freezing tolerance (FT) and to promote flowering through vernalization. Using different molecular and genomic approaches, several LT- responsive genes were identified from freezing tolerant wheat and rye in our laboratory. Expression analyses revealed that several of these genes are differentially expressed in winter and spring genotypes. Their expression was associated with the vernalization response and the capacity of wheat cultivars and other cereal species to cold acclimate and develop FT. Molecular and genetic studies designed to explain this differential expression have demonstrated that the level and duration of gene expression determine the degree of FT and depend on the vernalization response. As a consequence, the less tolerant spring cultivars, which do not require vernalization, cannot maintain the LT responsive genes in an up-regulated state. This limits their ability to achieve the same levels of FT as the vernalization responsive hardy winter cultivars. These genes and their products may have an important function in conferring FT and controlling flowering time. The goal of this research program is to understand the complex genetic mechanisms that control LT tolerance and vernalization. To achieve this goal, we will focus on the following objectives: 1) Identify and characterize the regulatory mechanisms and the signalling pathway that sense the cold and control the expression of the LT responsive genes. We will focus on the epigenetic regulation of cold response at both histone modifications and DNA methylation. In addition, the role of microRNAs and methyl-jasmonate in regulating these mechanisms will be studied; 2) determine the molecular and genetic connections between vernalization and cold acclimation. Understanding the molecular genetics of FT and flowering in temperate cereals will facilitate the development of the technology to manipulate these multigenic traits and produce crop species with sustainable production under changing climate conditions. This will have a tremendous impact on Canadian and world agriculture.