Biology subjects

La Rocca, N.

Publications and source records attributed to La Rocca, N..

3 recordsLinked to original sources

bioRxiv2026

Is constitutive red-shift an advantage for oxygenic photosynthesis under M-dwarf starlight? Insights from Acaryochloris marina sp. str. Moss Beach

In the next years, several space missions will search for evidence of life on exoplanets, focusing on robust biosignatures associated with oxygenic photosynthesis, including atmospheric oxygen accumulation and the Vegetation Red-Edge in surface reflectance spectra. Many potentially habitable rocky exoplanets orbit M-dwarf stars, whose spectral energy distribution may challenge oxygenic photosynthesis. Differently from the Sun, M-dwarf stars emit predominantly far-red (700- 750 nm) and infrared (750-1000 nm) light, and relatively little visible (400-700 nm) radiation, which constitutes photosynthetically active radiation. Some organisms have been found to photosynthesize under such spectrum but less efficiently than under solar light, as their photosynthetic apparatus evolved to harvest visible light emitted by the Sun. Around M-dwarfs, such different irradiation might have selected adaptations optimized for harvesting far-red / infra-red light. On Earth, similar selection can be found in Acaryochloris marina strains, constitutively presenting high chlorophyll d content in photosystem II & I, with in vivo absorption peaks beyond 700 nm. Here we tested the Moss Beach strain under a simulated M-dwarf spectrum and a simulated primeval atmosphere - anoxic and enriched in carbon dioxide. Results underline how this permanently red-shifted photosynthetic apparatus does not require acclimation to the stellar spectrum and enables for a strong growth and oxygen production, higher than under simulated solar light. Moreover, cells reflectance spectrum highlights a shift of the canonical red-edge toward longer wavelengths, resulting in a Chl d-near-infrared edge, suggesting a similar metabolism on exoplanets orbiting M-dwarfs could successfully produce both a gaseous biosignature and a characteristic surface biosignature. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=144 SRC="FIGDIR/small/719884v1_ufig1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@7f91bdorg.highwire.dtl.DTLVardef@1391bdborg.highwire.dtl.DTLVardef@53f7b4org.highwire.dtl.DTLVardef@ab59fa_HPS_FORMAT_FIGEXP M_FIG C_FIG Created in BioRender. Liistro, E. (2026) https://BioRender.com/j2de4ay

plant biology↗

bioRxiv2025

Enhanced carotenoid photoprotection in Far-Red light acclimated Chroococcidiopsis thermalis

Oxygenic photosynthesis is mainly driven by visible light in most photosynthetic organisms. However, some cyanobacteria strains can reversibly remodel their photosynthetic apparatus in order to rely exclusively on far-red photons. This acclimation, known as FaRLiP, requires the synthesis of red-shifted pigments, chlorophyll d, chlorophyll f and far-red allophycocyanin, that are incorporated in paralog subunits of the main photosynthetic complexes, namely photosystem II and photosystem I as well as phycobilisomes. In addition, some far-red-acclimating strains were also observed to show a rise in the carotenoid content and in the expression of genes involved in the biosynthesis of UV-shielding molecules, suggesting a counterintuitive photoprotective response concomitant with acclimation to lower energy wavelengths. In this work we investigated the response of Chroococcidiopsis thermalis to far-red light, and identified a robust set of photoprotective mechanisms associated with acclimation. Enhanced carotenoid/chlorophyll content ratios correlated with stronger carotenoid-chlorophyll triplet quenching, particularly pronounced for red-shifted chlorophylls. Non-photochemical quenching was higher and activated more rapidly than in cells grown under simulated solar light, and this was accompanied by enhanced antioxidant activity. Collectively, these findings indicate that the far-red acclimated cells, whose photosynthetic apparatus is not optimal under visible light, exhibit a strong photoprotected state, that we propose to be crucial under fluctuating irradiance conditions and during transitions from shaded to non-shaded environments. HighlightsO_LIFar-red light photoacclimation (FaRLiP) in Chroococcidiopsis thermalis is associated with an increased carotenoid-to-chlorophyll ratio. The relative abundance of myxol-2 fucoside, echinenone and {beta}-carotene increased in cells acclimated to far-red light compared with cells acclimated to simulated solar irradiation. C_LIO_LIUpon establishment of FaRLiP an exceptionally strong chlorophyll triplet quenching by carotenoids was observed, and it was specifically involving red-shifted chlorophylls. C_LIO_LIWhen exposed to the same light treatment, non-photochemical quenching was higher in far-red-acclimated cells than in solar-acclimated. Moreover, following high visible-light stress, far-red-acclimated cells exhibited lower levels of reactive oxygen species. The FaRLiP photosynthetic apparatus is safeguarded by robust mechanisms of photoprotection. C_LI

plant biology↗

bioRxiv2025

Thylakoids reorganization enables driving photosynthesis under far-red light in the microalga Nannochloropsis gaditana

O_LIOxygenic photosynthesis is driven by visible light in most photosynthetic organisms, with exceptions in few cyanobacteria and microalgae species, that can extend the light absorption to far-red wavelengths, by synthesizing new pigments or shifting the antennae absorption range beyond 700 nm. C_LIO_LIIn this work, we describe a novel mechanism of acclimation in the marine microalga Nannochloropsis gaditana, that resulted capable of growth relying solely on far-red light. Unexpectedly, the response did not involve the synthesis of red-shifted absorption forms, rather a peculiar reorganization of chloroplasts. C_LIO_LIThe abundance of photosynthetic complexes changed, with an increased accumulation of all pigment binding proteins and photosystem II. Chloroplasts became bigger and thylakoid membranes increased in number occupying almost all the organelle volume, showing also newly observed structures, composed of a central superstack with perpendicular electrondense interconnections, that we propose to name thylakoidal bodies. C_LIO_LITo the best of our knowledge, these results describe a novel acclimation strategy to far-red light, overall highlighting that the biodiversity of responses to far-red light is currently underestimated. C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=174 SRC="FIGDIR/small/665317v1_ufig1.gif" ALT="Figure 1"> View larger version (60K): org.highwire.dtl.DTLVardef@6d9038org.highwire.dtl.DTLVardef@1178b53org.highwire.dtl.DTLVardef@bc0e4corg.highwire.dtl.DTLVardef@4eb999_HPS_FORMAT_FIGEXP M_FIG C_FIG

plant biology↗