Cellular and molecular basis of low temperature tolerance in cereals

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Winter cereals regulate their development through two important evolutionary adaptive mechanisms: vernalization and freezing tolerance (FT). Vernalization postpones the transition from the vegetative to the reproductive phase, allowing plants to overwinter before flowering under favourable conditions for sexual reproduction. This process is closely associated with cold acclimation (CA) and the development of FT. Using different molecular and genomic approaches, several low temperature(LT) and vernalization responsive genes were identified from freezing tolerant wheat and rye in our laboratory. Expression analyses demonstrated that several genes are differentially expressed in winter and spring genotypes and their expression was associated with the vernalization response and the capacity of wheat cultivars and other cereal species to 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 basic goal of this research program is to understand the complex genetic mechanisms that control FT and vernalization. To achieve this goal, we will focus on the following objectives: 1) Identify the regulatory networks modulating the response to LT and vernalization in cereals, 2) Determine the mechanisms regulating the genetic links between vernalization and CA, 3) Identify microRNA(s) involved in FT and floral development. 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.