Walking the Edges – Probing the Limits of Near-UV and Near-IR Photosynthesis

Photosynthesis, fundamental to both terrestrial and aquatic ecosystems, has traditionally been understood as a process driven by visible light absorbed by chlorophyll a and canonical photosystems. However, recent research has revealed unexpected complexity in the photosynthetic action spectrum, particularly through the discovery of cyanobacteria and other microorganisms capable of using far-red and near-infrared light beyond 700 nm. These organisms employ alternative pigments such as chlorophyll d and f and exhibit far-red light photoacclimation mechanisms, effectively extending the energetic threshold for oxygen evolution. Similarly, certain anoxygenic phototrophs achieve even longer wavelength absorption with bacteriochlorophylls, providing crucial insights into the lower-energy limits of light-driven metabolism. On the opposite end of the spectrum, chlorophyll a can utilize near-ultraviolet light through its Soret band absorption, but the ecological and physiological roles of such high-energy photons remain only partially understood. Together, these discoveries have challenged long-held assumptions about the energetic constraints of photosynthesis and opened new lines of inquiry into its diversity, adaptability, and potential signatures beyond Earth.This Research Topic aims to elucidate the physiological, biochemical, and ecological mechanisms that enable photosynthetic organisms to function at the spectral margins of sunlight. By integrating experimental, theoretical, and comparative studies across oxygenic and anoxygenic systems, it seeks to define the limits of photon energy utilization and to identify the evolutionary and structural factors that govern pigment adaptation and efficiency. A central goal is to evaluate whether and how photosynthesis can sustain growth, perform oxygen evolution, and maintain energy balance when reliant solely on near-infrared or near-UV illumination. In doing so, the Research Topic will promote a deeper understanding of the energetic thresholds that constrain life’s ability to harness light and its implications for biosignature detection on habitable worlds.This Research Topic welcomes contributions that explore the physiological, biochemical, and ecological boundaries of light-driven energy conversion in phototrophic organisms. Emphasizing chlorophyll-based systems while encouraging comparative insights from anoxygenic phototrophs, it seeks to foster interdisciplinary research linking photobiology, biophysics, ecology, and planetary science. To gather further insights in these areas, we welcome articles addressing, but not limited to, the following themes:• Physiology and growth analysis under exclusive near-IR or near-UV illumination• Mechanistic basis and ecological significance of far-red light photoacclimation• Energetics and redox constraints of Photosystem II and anoxygenic reaction centers under low photon energy• Soret-band-driven photochemistry and its physiological relevance• Mechanisms of photodamage and photoprotection in near-UV conditions• Distribution and habitat specialization of long-wavelength phototrophs• Evolutionary perspectives on pigment adaptation and diversification• Modeling spectral efficiency, productivity, and ecological impact• Astrobiological implications for the detection of oxygenic biosignatures on exoplanets• Comparative spectral limits across oxygenic and anoxygenic phototrophs Topic editors: Marcel Dann, Tomáš Zavrel Source: https://www.frontiersin.org/research-topics/78723/walking-the-edges---probing-the-limits-of-near-uv-and-near-ir-photosynthesis