Back to the Seabed: The Unique Photosystem I Architecture of the Seagrass Posidonia oceanica

Back to the Seabed: The Unique Photosystem I Architecture of the Seagrass Posidonia oceanica | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Back to the Seabed: The Unique Photosystem I Architecture of the Seagrass Posidonia oceanica Roberto Bassi, Antonello Amelii, Stefano Capaldi, Mattia Russo, and 8 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8575725/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted You are reading this latest preprint version Abstract Seagrasses are marine angiosperms re-adapted to underwater life, forming productive ecosystems and long-term carbon sinks. Posidonia oceanica thrives up to 50 m depth, where light is scarce and spectrally shifted; yet, the molecular basis of its photosynthetic adaptation remains unclear. We showed that P. oceanica is genetically adapted to perform highly efficient photon use under dim light by enhancing photosystems antenna size and reducing exciton trapping time. We solved the structures of P. oceanica PSI supercomplexes by cryo-electron microscopy, revealing an expanded antenna system composed of PSI-LHCI, a trimeric phospho-LHCII, and an additional LHCI heterodimer. Low-energy chlorophyll spectral forms associated to LHCI, which modulate antenna-to-reaction center excitation transfer, are lost. Ultrafast spectroscopy revealed that this loss results in faster exciton trapping, thus compensating for antenna expansion and loss of quantum efficiency under dim light. Key residues responsible for the loss of low-energy forms were identified; replacing them with land-plant orthologs restored red-shifted emission, providing strategies to enhance light-use efficiency in crops. Biological sciences/Plant sciences/Photosynthesis/Photosystem I Biological sciences/Structural biology/Electron microscopy/Cryoelectron microscopy Biological sciences/Ecology/Ecophysiology Biological sciences/Plant sciences/Plant evolution Biological sciences/Plant sciences/Photosynthesis/Antenna complex Full Text Additional Declarations There is NO Competing Interest. Supplementary Files SupplementaryDataS1.FRETEETvaluesforPSILHCImegaAmeliietal.xlsx Data S1. EMD54396validationreport.pdf EMD-54396 validation report EMD54443validationreport.pdf EMD-54443 validation report EMD54441validationreport.pdf EMD-54441 validation report EMD54379validationreport.pdf EMD-54379 validation report EMD54380validationreport.pdf EMD-54380 validation report EMD54439validationreport.pdf EMD-54439 validation report EMD54444validationreport.pdf EMD-54444 validation report PDB9S1Lvalidationreport.pdf PDB 9S1L validation report PDB9S1Mvalidationreport.pdf PDB 9S1M validation report ReportingSummaryAmeliietal.pdf Reporting Summary Nature Portfolio_Amelii et al. AuthorizationforseagrassharvestingAmeliietal.pdf Authorization for seagrass harvesting_Amelii et al SupplementaryInformationAmeliietal.docx Supplementary Information Cite Share Download PDF Status: Under Review Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8575725","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":585257077,"identity":"6aa1d181-619c-431a-ae97-dec54c4c4187","order_by":0,"name":"Roberto 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