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