Light serves as the source of energy as well as an information signal for photosynthetic plants. During evolution, plants have acquired the ability to monitor environmental light radiation and adjust their developmental patterns to optimally utilize light energy for photosynthesis. The mechanisms of light perception and signal transduction have been comprehensively studied in past decades, mostly in a few model plants, including Arabidopsis thaliana. However, systematic analyses of the origin and evolution of core components involved in light perception and signaling are still lacking. In this study, we took advantage of the recently sequenced genomes and transcriptomes covering all the main Archaeplastida clades in the public domain to identify orthologous genes of core components involved in light perception and signaling and to reconstruct their evolutionary history. Our analyses suggested that acclimation to different distribution of light quality in new environments led to the origination of specific light signaling pathways in plants. The UVR8 (UV Resistance Locus 8) signaling pathway originated during the movement of plants from the deeper sea to shallow water and enabled plants to deal with ultraviolet B light (UV-B). After acquisition of UV-B adaptation, origination of the phytochrome signaling pathway helped plants to colonize water surface where red light became the prominent light energy source. The seedling emergence pathway, which is mediated by a combination of light and phytohormone signals that orchestrate plant growth pattern transitions, originated before the emergence of seed plants. Although cryptochromes and some key components of E3 ubiquitin ligase systems already existed before the divergence of the plant and animal kingdoms, the coevolution and optimization of light perception and downstream signal transduction components, including key transcription factors and E3 ubiquitin ligase systems, are evident during plant terrestrialization.

光既是能源，又是光合作用植物的信息信号。在进化过程中，植物获得了监测环境光辐射并调整其发育方式以最佳地利用光能进行光合作用的能力。在过去的几十年中，已经对光感知和信号转导的机制进行了全面的研究，其中大部分是在一些拟南芥植物中进行的，包括拟南芥。然而，仍然缺乏对涉及光感知和信号传导的核心成分的起源和进化的系统分析。在这项研究中，我们利用了覆盖公共领域所有主要古细菌分支的最近测序的基因组和转录组，来鉴定参与光感知和信号传导的核心成分的直系同源基因，并重建它们的进化历史。我们的分析表明，适应新环境中光质量的不同分布会导致植物中特定光信号通路的起源。UVR8（抗紫外线基因座8）信号通路起源于植物从深海向浅水运动的过程中，使植物能够处理紫外线B光（UV-B）。获得UV-B适应性后，植物色素信号通路的起源帮助植物在水表面定居，其中红光成为主要的光能源。幼苗出苗途径是由种子植物出苗之前发起的，通过光和植物激素信号的结合来协调植物的生长方式转变。尽管在动植物界分化之前就已经存在隐色染料和E3泛素连接酶系统的一些关键成分，但是在植物生长期间，光感知和下游信号转导成分（包括关键转录因子和E3泛素连接酶系统）的协同进化和优化是显而易见的。陆地化。它是由光和植物激素信号的组合介导的，这些信号协调植物的生长模式转变，起源于种子植物出现之前。尽管在动植物界分化之前就已经存在隐色染料和E3泛素连接酶系统的一些关键成分，但是在植物生长期间，光感知和下游信号转导成分（包括关键转录因子和E3泛素连接酶系统）的协同进化和优化是显而易见的。陆地化。它是由光和植物激素信号的组合介导的，这些信号协调植物生长模式的转变，起源于种子植物出现之前。尽管在动植物界分化之前就已经存在隐色染料和E3泛素连接酶系统的一些关键成分，但是在植物生长期间，光感知和下游信号转导成分（包括关键转录因子和E3泛素连接酶系统）的协同进化和优化是显而易见的。陆地化。