Data from: The origin and evolution of phototropins

Plant phototropism, the ability to bend toward or away from light, is predominantly controlled by blue-light photoreceptors, the phototropins. Although phototropins have been well-characterized in Arabidopsis thaliana, their evolutionary history is largely unknown. In this study, we complete an in-depth survey of phototropin homologs across land plants and algae using newly available transcriptomic and genomic data. We show that phototropins originated in an ancestor of Viridiplantae (land plants + green algae). Phototropins repeatedly underwent independent duplications in most major land-plant lineages (mosses, lycophytes, ferns, and seed plants), but remained single-copy genes in liverworts and hornworts—an evolutionary pattern shared with another family of photoreceptors, the phytochromes. Following each major duplication event, the phototropins differentiated in parallel, resulting in two specialized, yet partially overlapping, functional forms that primarily mediate either low- or high-light responses. Our detailed phylogeny enables us to not only uncover new phototropin lineages, but also link our understanding of phototropin function in Arabidopsis with what is known in Adiantum and Physcomitrella (the major model organisms outside of flowering plants). We propose that the convergent functional divergences of phototropin paralogs likely contributed to the success of plants through time in adapting to habitats with diverse and heterogeneous light conditions.

植物向光性（Plant phototropism）指植物朝向或背离光源弯曲的能力，其调控主要依赖蓝光受体（blue-light photoreceptors）——向光素（phototropins）。尽管向光素在拟南芥（Arabidopsis thaliana）中已得到充分解析，但其演化历史仍在很大程度上尚不明确。本研究借助新近公开的转录组与基因组数据，对陆生植物及藻类中的向光素同源基因开展了全面深入的普查。研究结果显示，向光素起源于绿色植物总界（Viridiplantae，包含陆生植物与绿藻）的共同祖先。在多数主要陆生植物类群（苔藓植物、石松类植物、蕨类植物与种子植物）中，向光素先后发生了多次独立复制事件，但在地钱类与角苔类植物中始终维持单拷贝基因状态——这一演化模式与另一类光受体家族光敏色素（phytochromes）的演化模式一致。在每次主要复制事件后，向光素均发生平行分化，最终形成两种特化但功能部分重叠的功能亚型，分别主要介导低光与高光响应。本研究构建的精细系统发育树不仅帮助我们发现了新的向光素谱系，还将我们对拟南芥向光素功能的认知，与开花植物以外的两类主流模式生物——铁线蕨属（Adiantum）与小立碗藓（Physcomitrella）中的相关研究成果建立了关联。我们推测，向光素旁系同源基因的趋同功能分化，可能助力植物在漫长的演化历程中更好地适应多样且异质的光照生境。