Response of the seagrass Posidonia oceanica to different light environments: Insights from a combined molecular and photo-physiological study E. Dattolo a, *, 2 , M. Ruocco a, 1 , 2 , C. Brunet a , M. Lorenti a , C. Lauritano a , D. D'Esposito a , P. De Luca a , R. Sanges a , S. Mazzuca b , G. Procaccini a a Stazione Zoologica Anton Dohrn, Villa Comunale, 80121 Napoli, Italy b Laboratorio di Proteomica, Dipartimento di Chimica e Tecnologie Chimiche, Universit a della Calabria, Arcavacata di Rende 87036, Italy article info Article history: Received 13 May 2014 Received in revised form 18 July 2014 Accepted 21 July 2014 Available online xxx Keywords: Photosynthesis Seagrass Gene expression cDNA-microarray RT-qPCR Light-response Pigments abstract Here we investigated mechanisms underlying the acclimation to light in the marine angiosperm Pos- idonia oceanica, along its bathymetric distribution (at 5 m and 25 m), combining molecular and photo-physiological approaches. Analyses were performed during two seasons, summer and autumn, in a meadow located in the Island of Ischia (Gulf of Naples, Italy), where a genetic distinction between plants growing above and below the summer thermocline was previously revealed. At molecular level, analyses carried out using cDNA-microarray and RT-qPCR, revealed the up-regulation of genes involved in photoacclimation (RuBisCO, ferredoxin, chlorophyll binding proteins), and photoprotection (antioxi- dant enzymes, xanthophyll-cycle related genes, tocopherol biosynthesis) in the upper stand of the meadow, indicating that shallow plants are under stressful light conditions. However, the lack of photo- damage, indicates the successful activation of defense mechanisms. This conclusion is also supported by several responses at physiological level as the lower antenna size, the higher number of reaction centers and the higher xanthophyll cycle pigment pool, which are common plant responses to high-light adaptation/acclimation. Deep plants, despite the lower available light, seem to be not light-limited, thanks to some shade- adaptation strategies (e.g. higher antenna size, lower E k values). Furthermore, also at the molecular level there were no signs of stress response, indicating that, although the lower energy available, low- light environments are more favorable for P. oceanica growth. Globally, results of whole transcriptome analysis displayed two distinct gene expression signatures related to depth distribution, reflecting the different light-adaptation strategies adopted by P. oceanica along the depth gradient. This observation, also taking into account the genetic disjunction of clones along the bathymetry, might have important implications for micro-evolutionary processes happening at meadow scale. Further investigations in controlled conditions must be performed to respond to these questions. © 2014 Elsevier Ltd. All rights reserved. 1. Introduction Marine angiosperms (seagrasses) are able to grow from the surface to ~50 m depth (Duarte, 1991), although records exist for their distribution down to 90 m (see Dalla Via et al., 1998 and references therein). The deeper limit of seagrass distribution depends on specific features of single species and correlates with the local light attenuation coefficients, influenced by both natural and human driven processes (Duarte, 1991; Ralph et al., 2007). Irradiance decreases exponentially along the water column, and also the light spectral quality is rapidly altered, shifting from the sunlight spectrum into a narrow band of blue-green light, due to water absorption and scattering processes (Kirk, 2011). In the clearest oceanic waters, blue light reaches the greatest depth, while in the coastal shallow water, with high scattering, light at- tenuates first and green light penetrates deeper (Kirk, 2011). Moreover, light is further attenuated due to self-shading inside the * Corresponding author. Tel.: þ39 0815833236. E-mail addresses: dattolo@szn.it, emanudat@gmail.com (E. Dattolo). 1 Present address: CCMAR e Centre of Marine Sciences, 8005-139 Faro, Portugal. 2 These authors made equal contribution to this work. Contents lists available at ScienceDirect Marine Environmental Research journal homepage: www.elsevier.com/locate/marenvrev http://dx.doi.org/10.1016/j.marenvres.2014.07.010 0141-1136/© 2014 Elsevier Ltd. All rights reserved. Marine Environmental Research xxx (2014) 1e12 Please cite this article in press as: Dattolo, E., et al., Response of the seagrass Posidonia oceanica to different light environments: Insights from a combined molecular and photo-physiological study, Marine Environmental Research (2014), http://dx.doi.org/10.1016/j.marenvres.2014.07.010