INRA, UMR 1095 GDEC (Génétique, Diversité et Ecophysiologie des Céréales), 234 Avenue du Brézet, Clermont-Ferrand 63100, France.
J Exp Bot. 2012 Jan;63(2):847-57. doi: 10.1093/jxb/err316. Epub 2011 Oct 12.
The initiation of flowering is a crucial trait that allows temperate plants to flower in the favourable conditions of spring. The timing of flowering initiation is governed by two main mechanisms: vernalization that defines a plant's requirement for a prolonged exposure to cold temperatures; and photoperiod sensitivity defining the need for long days to initiate floral transition. Genetic variability in both vernalization and photoperiod sensitivity largely explains the adaptability of cultivated crop plants such as bread wheat (Triticum aestivum L.) to a wide range of climatic conditions. The major genes controlling wheat vernalization (VRN1, VRN2, and VRN3) and photoperiod sensitivity (PPD1) have been identified, and knowledge of their interactions at the molecular level is growing. However, the quantitative effects of temperature and photoperiod on these genes remain poorly understood. Here it is shown that the distinction between the temperature effects on organ appearance rate and on vernalization sensu stricto is crucial for understanding the quantitative effects of the environmental signal on wheat flowering. By submitting near isogenic lines of wheat differing in their allelic composition at the VRN1 locus to various temperature and photoperiod treatments, it is shown that, at the whole-plant level, the vernalization process has a positive response to temperature with complex interactions with photoperiod. In addition, the phenotypic variation associated with the presence of different spring homoeoalleles of VRN1 is not induced by a residual vernalization requirement. The results demonstrate that a precise definition of vernalization is necessary to understand and model temperature and photoperiod effects on wheat flowering. It is suggested that this definition should be used as the basis for gene expression studies and assessment of functioning of the wheat flowering gene network, including an explicit account of the quantitative effect of environmental variables.
开花的启动是一个关键特征，使温带植物能够在春季的有利条件下开花。开花启动的时间由两个主要机制控制：春化作用定义了植物对长时间低温暴露的需求；光周期敏感性定义了需要长日照来启动花转变。春化作用和光周期敏感性的遗传变异性在很大程度上解释了栽培作物（如面包小麦（Triticum aestivum L.））对广泛气候条件的适应性。控制小麦春化作用（VRN1、VRN2 和 VRN3）和光周期敏感性（PPD1）的主要基因已经被鉴定出来，并且它们在分子水平上的相互作用的知识正在不断增加。然而，温度和光周期对这些基因的定量影响仍知之甚少。这里表明，区分温度对器官出现率和春化作用的影响对于理解环境信号对小麦开花的定量影响至关重要。通过将 VRN1 基因座等位基因组成不同的近等基因系小麦置于不同的温度和光周期处理下，可以表明，在整个植株水平上，春化过程对温度有正响应，并且与光周期有复杂的相互作用。此外，与 VRN1 的不同春同源等位基因存在相关的表型变异不是由剩余春化作用需求诱导的。结果表明，精确定义春化作用对于理解和模拟温度和光周期对小麦开花的影响是必要的。建议将这个定义用作基因表达研究和评估小麦开花基因网络功能的基础，包括对环境变量的定量效应的明确说明。
