Cellular and molecular basis of low temperature tolerance in cereals

冬粮通过春化和耐寒两种重要的进化适应机制来调节它们的发育。春化推迟了从营养阶段到生殖阶段的过渡，使植物在开花前能够在有利的有性繁殖条件下越冬。这一过程与冷驯化(CA)和FT的发育密切相关。利用不同的分子和基因组方法，从本实验室的耐寒小麦和黑麦中分离到了几个低温和春化反应基因。表达分析表明，有几个基因在冬小麦和春小麦中存在差异表达，它们的表达与小麦品种和其他谷类作物的春化反应和发育能力有关。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，不需要春化的耐性较差的春季品种不能保持LT反应基因处于上调状态。这限制了它们达到与春化反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赋予FT和控制开花时间方面具有重要功能。这个研究项目的基本目标是了解控制FT和春化的复杂遗传机制。为了实现这一目标，我们将着重于以下目标：1)确定谷物对LT和春化反应的调控网络，2)确定春化和CA之间遗传联系的调控机制，3)鉴定参与FT和花发育的microRNA(S)。了解温带谷类作物开花和开花的分子遗传学将有助于技术的发展，以操纵这些多基因性状，并在不断变化的气候条件下生产出可持续生产的作物物种。这将对加拿大和世界农业产生巨大影响。

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.