SummaryPlant nutrition critically depends on the activity of membrane transporters that translocate minerals from the soil into the plant and are responsible for their intra-and intercellular distribution. Most plant membrane transporters are encoded by multigene families whose members often exhibit overlapping expression patterns and a high degree of sequence homology. Furthermore, many inorganic nutrients are transported by more than one transporter family. These considerations, coupled with a large number of so-far non-annotated putative transporter genes, hamper our progress in understanding how the activity of speci®c transporters is integrated into a response to¯uctuating conditions. We designed an oligonucleotide microarray representing 1096 Arabidopsis transporter genes and analysed the root transporter transcriptome over a 96-h period with respect to 80 mM NaCl, K starvation and Ca 2 starvation. Our data show that cation stress led to changes in transcript level of many genes across most transporter gene families. Analysis of transcriptionally modulated genes across all functional groups of transporters revealed families such as V-type ATPases and aquaporins that responded to all treatments, and families ± which included putative non-selective cation channels for the NaCl treatment and metal transporters for Ca 2 starvation conditions ± that responded to speci®c ionic environments. Several gene families including primary pumps, antiporters and aquaporins were analysed in detail with respect to the mRNA levels of different isoforms during ion stress. Cluster analysis allowed identi®cation of distinct expression pro®les, and several novel putative regulatory motifs were discovered within sets of co-expressed genes.

Early in its life cycle, the marine mollusc Elysia chlorotica Gould forms an intracellular endosymbiotic association with chloroplasts of the chromophytic alga Vaucheria litorea C. Agardh. As a result, the dark green sea slug can be sustained in culture solely by photoautotrophic CO 2 fixation for at least 9 months if provided with only light and a source of CO 2 . Here we demonstrate that the sea slug symbiont chloroplasts maintain photosynthetic oxygen evolution and electron transport activity through photosystems I and II for several months in the absence of any external algal food supply. This activity is correlated to the maintenance of functional levels of chloroplast-encoded photosystem proteins, due in part at least to de novo protein synthesis of chloroplast proteins in the sea slug. Levels of at least one putative algal nuclear encoded protein, a light-harvesting complex protein homolog, were also maintained throughout the 9-month culture period. The chloroplast genome of V. litorea was found to be 119.1 kb, similar to that of other chromophytic algae. Southern analysis and polymerase chain reaction did not detect an algal nuclear genome in the slug, in agreement with earlier microscopic observations. Therefore, the maintenance of photosynthetic activity in the captured chloroplasts is regulated solely by the algal chloroplast and animal nuclear genomes.

Please cite this paper as: Shoji et al. (2011) A plant‐based system for rapid production of influenza vaccine antigens. Influenza and Other Respiratory Viruses 6(3), 204–210. Background  Influenza virus is a globally important respiratory pathogen that causes a high degree of annual morbidity and mortality. Significant antigenic drift results in emergence of new, potentially pandemic, virus variants. The best prophylactic option for controlling emerging virus strains is to manufacture and administer pandemic vaccines in sufficient quantities and to do so in a timely manner without impacting the regular seasonal influenza vaccine capacity. Current, egg‐based, influenza vaccine production is well established and provides an effective product, but has limited capacity and speed. Objectives  To satisfy the additional global demand for emerging influenza vaccines, high‐performance cost‐effective technologies need to be developed. Plants have a potential as an economic and efficient large‐scale production platform for vaccine antigens. Methods  In this study, a plant virus‐based transient expression system was used to produce hemagglutinin (HA) proteins from the three vaccine strains used during the 2008–2009 influenza season, A/Brisbane/59/07 (H1N1), A/Brisbane/10/07 (H3N2), and B/Florida/4/06, as well as from the recently emerged novel H1N1 influenza A virus, A/California/04/09. Results  The recombinant plant‐based HA proteins were engineered and produced in Nicotiana benthamiana plants within 2 months of obtaining the genetic sequences specific to each virus strain. These antigens expressed at the rate of 400–1300 mg/kg of fresh leaf tissue, with >70% solubility. Immunization of mice with these HA antigens induced serum anti‐HA IgG and hemagglutination inhibition antibody responses at the levels considered protective against these virus infections. Conclusions  These results demonstrate the feasibility of our transient plant expression system for the rapid production of influenza vaccine antigens.

HighlightsReport of a Phase I clinical trial to assess a malaria transmission blocking vaccine.P. falciparum Pfs25 virus-like particle produced under cGMP in a plant-based system.The vaccine candidate displays an acceptable safety and tolerability profile.The vaccine candidate induced Pfs25-specific IgG in a dose dependent manner.However, low transmission reducing activity implies need for an improved formulation.

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