Cellular and molecular basis of low temperature tolerance in cereals

冬季谷物需要长时间暴露于低温（LT）中，以触发诱导抗冻性（FT）的遗传机制，并通过春化促进开花。利用不同的分子和基因组方法，我们从耐冻小麦和黑麦中鉴定了几个低温反应基因。表达分析表明，其中一些基因在冬季和春季基因型中存在差异表达。它们的表达与春化反应以及小麦品种和其他谷类品种的冷适应性和发育FT的能力有关。旨在解释这种差异表达的分子和遗传学研究表明，基因表达的水平和持续时间决定了FT的程度，并取决于春化反应。因此，不需要春化的耐受性较差的春季品种不能将LT反应基因维持在上调状态。这限制了它们获得与春化响应的耐寒冬季品种相同的FT水平的能力。这些基因及其产物可能在控制开花时间和FT中起重要作用。本研究计划的目标是了解控制LT耐受性和春化的复杂遗传机制。为了实现这一目标，我们将重点关注以下目标：1)识别和表征感知寒冷和控制低温反应基因表达的调控机制和信号通路。我们将重点关注组蛋白修饰和DNA甲基化对冷反应的表观遗传调控。此外，还将研究microrna和茉莉酸甲酯在调节这些机制中的作用；2)确定春化与冷驯化之间的分子和遗传联系。了解温带谷物中FT和开花的分子遗传学将促进技术的发展，以操纵这些多基因性状，并在不断变化的气候条件下生产可持续生产的作物品种。这将对加拿大和世界农业产生巨大影响。

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.