Department of Biochemistry , University of Wisconsin, Madison, Wisconsin 53706.
Plant Physiol. 2014 Feb;164(2):694-709. doi: 10.1104/pp.113.232678. Epub 2013 Dec 19.
Timing of flowering is key to the reproductive success of many plants. In temperate climates, flowering is often coordinated with seasonal environmental cues such as temperature and photoperiod. Vernalization is an example of temperature influencing the timing of flowering and is defined as the process by which a prolonged exposure to the cold of winter results in competence to flower during the following spring. In cereals, three genes (VERNALIZATION1 [VRN1], VRN2, and FLOWERING LOCUS T [FT]) have been identified that influence the vernalization requirement and are thought to form a regulatory loop to control the timing of flowering. Here, we characterize natural variation in the vernalization and photoperiod responses in Brachypodium distachyon, a small temperate grass related to wheat (Triticum aestivum) and barley (Hordeum vulgare). Brachypodium spp. accessions display a wide range of flowering responses to different photoperiods and lengths of vernalization. In addition, we characterize the expression patterns of the closest homologs of VRN1, VRN2 (VRN2-like [BdVRN2L]), and FT before, during, and after cold exposure as well as in different photoperiods. FT messenger RNA levels generally correlate with flowering time among accessions grown in different photoperiods, and FT is more highly expressed in vernalized plants after cold. VRN1 is induced by cold in leaves and remains high following vernalization. Plants overexpressing VRN1 or FT flower rapidly in the absence of vernalization, and plants overexpressing VRN1 exhibit lower BdVRN2L levels. Interestingly, BdVRN2L is induced during cold, which is a difference in the behavior of BdVRN2L compared with wheat VRN2 during cold.
开花时间是许多植物生殖成功的关键。在温带气候下,开花通常与季节性环境线索(如温度和光周期)相协调。春化作用是温度影响开花时间的一个例子,它被定义为植物长时间暴露在冬季寒冷中,导致其在随后的春季具有开花能力的过程。在谷类作物中,已经鉴定出三个影响春化要求的基因(VRN1、VRN2 和 FT),它们被认为形成了一个调控环,以控制开花时间。在这里,我们描述了短柄草(Brachypodium distachyon)春化和光周期反应的自然变异,短柄草是一种与小麦(Triticum aestivum)和大麦(Hordeum vulgare)相关的温带小禾本科植物。短柄草种的不同光周期和春化长度表现出广泛的开花反应。此外,我们还描述了 VRN1、VRN2(VRN2 样[BdVRN2L])和 FT 的最接近同源物在冷暴露前后以及不同光周期下的表达模式。在不同光周期下生长的不同品种中,FT mRNA 水平通常与开花时间相关,并且在冷后春化的植物中 FT 表达水平更高。VRN1 在叶片中受冷诱导,并在春化后持续高水平表达。过表达 VRN1 或 FT 的植物在没有春化的情况下迅速开花,而过表达 VRN1 的植物 BdVRN2L 水平较低。有趣的是,BdVRN2L 在冷诱导期间被诱导,这与小麦 VRN2 在冷期间的行为不同。