Light acts as a master switch in early plant growth, from cyanobacteria to seedlings

Light is far more than fuel for photosynthesis. In a new editorial published in Frontiers in Plant Physiology, researchers Jay Prakash Maurya of Banaras Hindu University and Siddhartha Dutta of Sister Nivedita University argue that light should be understood as an information-rich signal that lets photosynthetic organisms sense their surroundings and time their developmental transitions. The editorial introduces a Research Topic of five publications that trace how light governs early plant growth, from the first photoreceptors of cyanobacteria to the germination of medicinal tree seedlings, and it makes the case that the earliest light-driven decisions of a plant’s life echo through every later stage of development, ultimately shaping yield and survival under adverse conditions.

The scope of the collection is unusually broad. The five publications span cyanobacteria, algae, bryophytes and seed plants, including cereals and medicinal species, and together they illuminate both the conserved and diversified nature of light-signaling processes. According to the editors, the topic moves from photoreceptors and photomorphogenesis to chloroplast biogenesis, hormonal regulation and stress responses, assembling a cross-lineage picture of how organisms translate the quality and quantity of light they perceive into cascades of molecular and physiological processes that shape vegetative and reproductive growth.

Two reviews in the collection examine the evolutionary breadth of photoreceptors from prokaryotes to land plants. Pandey and colleagues review how cyanobacteria detect and respond to diverse light conditions. Beyond the familiar cyanobacterial phytochromes and rhodopsins, these organisms deploy specialized compact photoreceptors called cyanobacteriochromes, which cover the spectrum from near-ultraviolet to near-infrared. The review also addresses the role of the photosynthetic electron transport chain in regulating photosystem activity and digs into spectral tuning, including the mechanisms of chromatic acclimation, in which light-harvesting phycobilisomes are remodeled to optimize light absorption. All seven types of chromatic acclimation are distinguished, and the RcaE–RcaF–RcaC phosphorelay observed in the cyanobacterium Fremyella diplosiphon emerges as a paradigm for how a single photoreceptor system can couple pigment composition to cell morphology and even carboxysome organization.

Pradhan and colleagues take an evolutionary-developmental view across the green lineage, comparing light signaling in flowering plants with three simpler relatives: the unicellular alga Chlamydomonas reinhardtii, the liverwort Marchantia polymorpha and the moss Physcomitrium patens. In Chlamydomonas, light is sensed through channel rhodopsin proteins localized in the eyespot, along with UVR8, phototropins and cryptochromes, and no phytochromes have been reported so far; notably, the UVR8–COP1 module still resembles that of angiosperms. Marchantia carries only one copy of most light-signaling factors studied in the reference plant Arabidopsis, including single copies of cryptochrome, phytochrome and UVR8. A single phytochrome and one PIF transcription factor control gemma germination, meristem dormancy, branching and far-red responses in this liverwort.

Physcomitrium tells the opposite story of expansion. The moss possesses seven phytochromes, four PIFs, nine COP1 and two SPA proteins, and mutants lacking COP1 and SPA develop green chloroplasts even in darkness, revealing how gene duplication has rewired light-dependent development in this lineage. The editors draw a central conclusion from these comparisons: although the core process of light perception, transduction and response is conserved across the green lineage, the gene copy number, the signaling network architecture and the developmental outputs have diverged dramatically over evolutionary time.

A third review, by Sandhya and colleagues, zooms in on the morphogenic events that establish stable plant growth at the seedling stage: hypocotyl elongation, apical hook formation, cotyledon expansion and greening. The review provides updated knowledge on the molecular mechanisms of light signaling involved in seed germination, hypocotyl and cotyledon development, chloroplast biogenesis and root development, and explains how the environment modulates these light-driven processes. At the molecular level, the photoreceptors, COP1, PIFs and the transcription factor HY5 act as regulatory hubs that integrate multiple phytohormonal signaling networks toward achieving optimum seedling development, effectively serving as crossroads where light information and hormone status are reconciled.

One of the most intriguing threads in the Sandhya review concerns roots, which grow underground yet are profoundly influenced by light. The review explains how shoot-derived light signals, perceived through multiple photoreceptors and particularly the phytochromes, directly or indirectly modulate various aspects of root development. These include primary root elongation, lateral root initiation, root hair differentiation and both gravitropic and phototropic responses, the growth movements that orient roots relative to gravity and light. The picture that emerges is of a plant in which the illuminated shoot acts as a sensory organ for the hidden half of the organism, converting canopy light cues into instructions that sculpt root architecture.

A fourth review, by Kushwah and colleagues, examines the physiology behind the dormancy-to-growth transition of seeds, arguably the single most consequential decision in a plant’s life. The review explains how phytochrome-mediated degradation of the PIF proteins tilts the balance between the hormones abscisic acid and gibberellic acid toward germination, with abscisic acid maintaining dormancy and gibberellin promoting growth. The authors also compile updated information on the epigenetic machinery regulating this first decision, covering the roles of DNA methylation, histone modification, chromatin remodeling and small RNAs in the switch from dormancy to germination.

The Kushwah review adds a transgenerational dimension that the editors flag as a frontier for future work: the maternal environment, notably light alongside temperature and other factors, directly influences progeny behavior at early developmental stages. In other words, the light conditions experienced by a mother plant can leave marks that shape how her offspring germinate and grow. The editorial notes that this epigenetic influence of maternal light conditions on progeny remains largely unexplored, and the collection also emphasizes the significance of spatial and temporal variations in light signals, including their timing and duration, in shaping physiological responses.

The fifth contribution, a research article by Rowshanaie and colleagues, translates light biology into a practical cultivation strategy. The team investigated seedling growth of tongkat ali (Eurycoma longifolia Jack), a medicinal plant, under varying water availability and different levels of irradiance. The study showed that severe shading at 70 percent lowered the root-to-shoot ratio, the root mass ratio and overall growth, whereas 50 percent shading performed better than full light under mild water deficit. This finding underscores the significance of moderate, low-level radiation in seedling development of E. longifolia and illustrates how knowledge of light responses in higher plants can support conservation, domestication and enhanced crop growth rate. Taken together, the editors write, the articles not only discuss the role of light at early developmental phases but also elucidate how early light-mediated decisions modulate later developmental stages, and they hope the Research Topic will boost multidisciplinary studies on light signaling by identifying mechanistic gaps and exploring translational opportunities for crop improvement.

Subject of Research: Light regulation of early plant growth and development across photosynthetic organisms.

Article Title: Editorial: Light regulation of early plant growth and development

Article References: Maurya, J. P., & Dutta, S. (2026). Editorial: Light regulation of early plant growth and development. Frontiers in Plant Physiology, 4, Article 2033579. https://doi.org/10.3389/fphgy.2026.2033579

Image Credits: AI Generated

DOI: 10.3389/fphgy.2026.2033579

Keywords: light signaling, photoreceptors, photomorphogenesis, cyanobacteria, Chlamydomonas, Marchantia, Physcomitrium, seed germination, chloroplast biogenesis, epigenetics, Eurycoma longifolia, plant development