Abstract
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.
Highlights
Light is the ultimate source of energy for almost all of life on earth, and a remarkable diversity of organisms uses photosynthesis to convert light into metabolic energy
Our results suggest that phototropins likely originated in an ancestor of Viridiplantae
The Origin of Phototropins We show here that phototropins are present in all major land plant lineages, as well as in green algae
Summary
Light is the ultimate source of energy for almost all of life on earth, and a remarkable diversity of organisms uses photosynthesis to convert light into metabolic energy Many of these organisms have evolved phototropic/phototactic responses, and those in plants are sophisticated—involving movement of shoots, leaves, and/or chloroplasts—in order to optimize their photosynthetic capacity. Darwin proposed that a transmissible substance produced at the tip is responsible for inducing phototropic movements in plants. This insight led to the first discovery of a plant hormone, auxin, and later to the identification of the blue-light photoreceptors for Phototropin evolution phototropism—phototropins (Briggs et al, 2001; Christie and Murphy, 2013; Briggs, 2014). The orthology of phototropin genes has been ambiguous, confounding assignments of functional homology, and impeding our understanding of how phototropin evolution has allowed plants to adapt to light environments
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
