Response to Light Quality and Photoperiod in Arabidopsis: Plasticity and Pleiotropy

Pigliucci 9707552分子遗传学家和生理学家利用模式系统拟南芥实现了对两种不同形式的表型可塑性的详细机制理解：对光质量的反应和对光周期的反应。这些分析清楚地证明，控制这两种形式可塑性的基因之间存在广泛的重叠，这引发了关于多效性和遗传冗余的进化起源和生态影响的问题。PI对这些遗传细节的理解使我们能够解决一个复杂的问题：植物如何整合一套线索，这些线索提供关于多因素选择性环境的不同方面的信息？对于一年生植物来说，光质量是当前和迫在眉睫的光竞争的具体和可靠的线索，因为侵占竞争对手改变了光质量(即红光与远红光的比率-R：FR)。类似地，在生长拟南针的温带地区，光周期的长短是季节性的指标。自然种群能否在感知和响应光质线索的能力上对选择做出反应？R：FR介导的可塑性综合征和光周期介导的可塑性之间的关系有多强？PI将建议利用重复的选择和控制线进行短期选择试验。PI将与田纳西州东部已经在进行密集研究的大量自然种群合作。我们将直接根据R：FR介导的开花时间可塑性进行选择。在评估对直接选择的反应时，我们还将研究两种形式的间接反应。首先，在R：FR介导的其他性状的可塑性中是否有反应？其次，对同一性状，即开花时间，光周期介导的可塑性(即，不同的线索)是否有反应？PI计划解决性状之间的相互作用，并在一系列突变系中实现R：FR和光周期介导的可塑性。这些突变体缺乏影响包括生殖适合性在内的一系列特征的特定感光基因。此外，在这些突变株系及其相关的野生型中，正常和改变的可塑性模式发生在相同的遗传背景中。因此，可以对控制可塑性的一个或多个基因如何影响整个生物体，包括其性能或适应性(多效性)做出强有力的推断。

Pigliucci 9707552 Molecular geneticists and physiologists working with the model system Arabidopsis thaliana have achieved a detailed mechanistic understanding of two distinct forms of phenotypic plasticity: the response to light quality and the response to photoperiod. These analyses have clearly established that there is extensive overlap among the genes that regulate these two forms of plasticity, raising questions about the evolutionary origins and ecological implications of pleiotropy and genetic redundancy. The PIs' understanding of these genetic details allows us to address a complex question: how do plants integrate a suite of cues that provide information about different aspects of multifactor selective environments? For annual plants, light quality serves as a specific and reliable cue for present and imminent competition for light, because encroaching competitors alter light quality (i.e., the ratio of red to far-red light - R:FR). Similarly, in the temperate regions where A. thaliana grows, the length of the photoperiod is an indicator of seasonality. Can natural populations of A. thaliana respond to selection on the ability to sense and respond to light quality cues? How strong is the relationship, if any, between the R:FR-mediatedplasticity syndrome, andphotoperiod-mediated plasticity? The PIs will propose a short-term selection experiment with replicated selection and control lines. The PIs will work with a large natural population already under intensive study in East Tennessee. We will select directly on the R:FR-mediated plasticity of flowering time. While assessing the response to this direct selection, we will also examine two forms of indirect response. First, was there a response in the R:FR-mediated plasticity of other traits? Second, was there a response in the photoperiod-mediated plasticity (i.e., a different cue) of the same trait, flowering time? The PIs' plan to address the interaction among traits and be tween R:FR- and photoperiodmediated plasticity in a series of mutant lines. These mutants lack specific photoreceptor genes that affect a suite of traits, including reproductive fitness. Furthermore, in these mutant lines and their associated wild types, normal and altered patterns of plasticity occur in the same genetic background. Thus, it is possible to make strong inferences about how a gene (or genes) controlling plasticity affects the whole organism, including its performance or fitness (pleiotropy).