In this review we focus on a specific sub-branch of light-harvesting bioelectrochemical systems called biophotovoltaic systems.

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Recent advances in fuel cell (FC) and microbial fuel cell (MFC) research have demonstrated these electrochemical technologies as effective methods for generating electrical power from chemical fuels and organic compounds. This led to the development of MFC-inspired photovoltaic (BPV) devices that produce electrical power by harvesting solar energy through biological activities of photosynthetic organisms. We describe the fabrication of a BPV device with multiple microchannels. This allows a direct comparison between sub-cellular photosynthetic organelles and whole cells, and quantitative analysis of the parameters affecting power output. Electron transfer within the photosynthetic materials was studied using the metabolic inhibitors DCMU (3-(3,4-dichlorophenyl)-1,1-dimethylurea) and methyl viologen (1,1 0 -dimethyl-4,4 0 -bipyridinium dichloride). These experiments suggest that the electrons that cause an increase in power upon illumination leave the photosynthetic electron transfer chain from the reducing end of photosystem I. Several key factors limiting performance efficiency, including density of the photosynthetic catalyst, electron carrier concentration, and light intensity were investigated.

Recent advances in synthetic biology research have been underpinned by an exponential increase in available genomic information and a proliferation of advanced DNA assembly tools. The adoption of plasmid vector assembly standards and parts libraries has greatly enhanced the reproducibility of research and the exchange of parts between different labs and biological systems. However, a standardized modular cloning (MoClo) system is not yet available for cyanobacteria, which lag behind other prokaryotes in synthetic biology despite their huge potential regarding biotechnological applications. By building on the assembly library and syntax of the Plant Golden Gate MoClo kit, we have developed a versatile system called CyanoGate that unites cyanobacteria with plant and algal systems. Here, we describe the generation of a suite of parts and acceptor vectors for making (1) marked/unmarked knock-outs or integrations using an integrative acceptor vector, and (2) transient multigene expression and repression systems using known and previously undescribed replicative vectors. We tested and compared the CyanoGate system in the established model cyanobacterium Synechocystis sp. PCC 6803 and the more recently described fastgrowing strain Synechococcus elongatus UTEX 2973. The UTEX 2973 fast-growth phenotype was only evident under specific growth conditions; however, UTEX 2973 accumulated high levels of proteins with strong native or synthetic promoters. The system is publicly available and can be readily expanded to accommodate other standardized MoClo parts to accelerate the development of reliable synthetic biology tools for the cyanobacterial community.

Summary• The relationship in sugarcane ( Saccharum spp.) between photosynthetic source tissue and sink material was examined through manipulation of the sink:source ratio of field-grown Saccharum spp. hybrid cv. N19 (N19).• To enhance sink strength, all leaves, except for the third fully expanded leaf, were enclosed in 90% shade cloth for varying periods of time. Variations in sucrose, glucose and fructose concentrations were measured and the effects of shading on the leaf gas exchange and fluorescence characteristics recorded. Changes in carbon partitioning caused by shading were examined based on the uptake and translocation of fixed 14 CO 2 .• Following a decline in sucrose concentrations in young internodal tissue and shaded leaves, significant increases in the CO 2 -saturated photosynthetic rate ( J max ), carboxylation efficiency (CE) and electron transport rate were observed in unshaded leaves after 8 d of shading treatment.• It was concluded that up-regulation of source-leaf photosynthetic capacity is correlated with a decrease in assimilate availability to acropetal culm sink tissue. Furthermore, a significant relationship was revealed between source hexose concentration and photosynthetic activity.