Benthic litter in the continental slope of the Gulf of Naples (central-western Mediterranean Sea) hosts limited fouling communities but facilitates molluscan spawning.

Seafloor pollution by benthic litter is an emerging phenomenon, although debris colonization by biota remains largely unexplored. We characterized the litter of the continental slope (~400-600 m) of the Gulf of Naples (Mediterranean) and investigated its fouling biota through integrative taxonomic approaches. Plastic pieces (82 %) with land-based origin (96 %) and limited sizes (10-20 cm) were the items most commonly encountered, suggesting a transfer to deep waters through floating and sinking. The majority of the items were not fouled, and the debris hosted an impoverished biota, leading to hypothesize that benthic litter supports wide communities only in shallow waters. Higher colonization rates were observed for gastropod and cephalopod eggs with no preference for materials and sizes, suggesting that even small pieces of soft plastic provide a spawning habitat for molluscs and affect species' connectivity in the deep-sea ecosystem. Holistic approaches are necessary to evaluate interactions between litter and biota.

Fruit-specific RNAi-mediated suppression of DET1 enhances carotenoid and flavonoid content in tomatoes.

Tomatoes are a principal dietary source of carotenoids and flavonoids, both of which are highly beneficial for human health. Overexpression of genes encoding biosynthetic enzymes or transcription factors have resulted in tomatoes with improved carotenoid or flavonoid content, but never with both. We attempted to increase tomato fruit nutritional value by suppressing an endogenous photomorphogenesis regulatory gene, DET1, using fruit-specific promoters combined with RNA interference (RNAi) technology. Molecular analysis indicated that DET1 transcripts were indeed specifically degraded in transgenic fruits. Both carotenoid and flavonoid contents were increased significantly, whereas other parameters of fruit quality were largely unchanged. These results demonstrate that manipulation of a plant regulatory gene can simultaneously influence the production of several phytonutrients generated from independent biosynthetic pathways, and provide a novel example of the use of organ-specific gene silencing to improve the nutritional value of plant-derived products.

Molecular toolbox for studying diatom biology in Phaeodactylum tricornutum.

Research into diatom biology has now entered the post-genomics era, following the recent completion of the Thalassiosira pseudonana and Phaeodactylum tricornutum whole genome sequences and the establishment of Expressed Sequence Tag (EST) databases. The thorough exploitation of these resources will require the development of molecular tools to analyze and modulate the function of diatom genes in vivo. Towards this objective, we report here the identification of several reference genes that can be used as internal standards for gene expression studies by quantitative real-time PCR (qRT-PCR) in P. tricornutum cells grown over a diel cycle. In addition, we describe a series of diatom expression vectors based on Invitrogen Gateway technology for high-throughput protein tagging and overexpression studies in P. tricornutum. We demonstrate the utility of the diatom Destination vectors for determining the subcellular localization of a protein of interest and for immunodetection. The availability of these new resources significantly enriches the molecular toolbox for P. tricornutum and provides the diatom research community with well defined high-throughput methods for the analysis of diatom genes and proteins in vivo.

Light modulation of biomass and macromolecular composition of the diatom Skeletonema marinoi.

The biochemical profile and growth of the coastal diatom Skeletonema marinoi was investigated under four different daily blue light doses (sinusoidal light peaking at 88, 130, 250 and 450 µmol photons m(−2) s(−1), respectively). Ability of cells to regulate the light energy input caused alterations in growth and different biosynthetic pathways. The light saturation index for photosynthesis (E(k)), which governs the photoacclimative processes, ranged between 250 and 300 µmol photons m(−2) s(−1). Cells that were adapted to low light (

Manipulation of DET1 expression in tomato results in photomorphogenic phenotypes caused by post-transcriptional gene silencing.

The tomato HIGH PIGMENT-2 gene encodes an orthologue of the Arabidopsis nuclear protein DE-ETIOLATED 1 (DET1). From genetic analyses it has been proposed that DET1 is a negative regulator of light signal transduction, and recent results indicate that it may control light-regulated gene expression at the level of chromatin remodelling. To gain further understanding about the function of DET1 during plant development, we generated a range of overexpression constructs and introduced them into tomato. Unexpectedly, we only observed phenotypes characteristic of DET1 inactivation, i.e. hyper-responsiveness to light. Molecular analysis indicated in all cases that these phenotypes were a result of suppression of endogenous DET1 expression, due to post-transcriptional gene silencing. DET1 silencing was often lethal when it occurred at relatively early stages of plant development, whereas light hyper-responsive phenotypes were obtained when silencing occurred later on. The appearance of phenotypes correlated with the generation of siRNAs but not DNA hypermethylation, and was most efficient when using constructs with mutations in the DET1 coding sequence or with constructs containing only the 3'-terminal portion of the gene. These results indicate an important function for DET1 throughout plant development and demonstrate that silencing of DET1 in fruits results in increased carotenoids, which may have biotechnological potential.