Dataset Information

Photosynthesis in a different light: spectro-microscopy for in vivo characterization of chloroplasts.

ABSTRACT: During photosynthesis, energy conversion at the two photosystems is controlled by highly complex and dynamic adaptation processes triggered by external factors such as light quality, intensity, and duration, or internal cues such as carbon availability. These dynamics have remained largely concealed so far, because current analytical techniques are based on the investigation of isolated chloroplasts lacking full adaptation ability and are performed at non-physiologically low temperatures. Here, we use non-invasive in planta spectro-microscopic approaches to investigate living chloroplasts in their native environment at ambient temperatures. This is a valuable approach to study the complex function of these systems, because an intrinsic property-the fluorescence emission-is exploited and no additional external perturbations are introduced. Our analysis demonstrates a dynamic adjustment of not only the photosystemI/photosystemII (PSI/PSII) intensity ratio in the chloroplasts but also of the capacity of the LHCs for energy transfer in response to environmental and internal cues.

SUBMITTER: Peter S

PROVIDER: S-EPMC4082301 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Photosynthesis in a different light: spectro-microscopy for in vivo characterization of chloroplasts.

Peter Sébastien S Zell Martina B MB Blum Christian C Stuhl Alexander A Elgass Kirstin K Sackrow Marcus M Subramaniam Vinod V Meixner Alfred J AJ Harter Klaus K Maurino Veronica G VG Schleifenbaum Frank E FE

Frontiers in plant science 20140630

During photosynthesis, energy conversion at the two photosystems is controlled by highly complex and dynamic adaptation processes triggered by external factors such as light quality, intensity, and duration, or internal cues such as carbon availability. These dynamics have remained largely concealed so far, because current analytical techniques are based on the investigation of isolated chloroplasts lacking full adaptation ability and are performed at non-physiologically low temperatures. Here, ...[more]

PMID: 25071790

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Project description:Simple Summary Kleptoplasty is the capacity of a non-photosynthetic organism to acquire and maintain structurally intact chloroplasts from its algal food source(s), thereafter termed kleptoplasts. In animals, the capacity for long-term (several weeks to months) maintenance of photosynthetic active kleptoplasts is a unique characteristic in a handful of sea slugs, mostly within the genus Elysia. In this study, we investigated the role of kleptoplast photosynthesis on mucus production by the tropical sea slug Elysia crispata. Mucus secretion is paramount for mollusks, playing a role in locomotion, feeding, reproduction and protection. Limiting photosynthesis by rearing animals under reduced light led to lower mucus production and lower carbohydrate concentrations in the secreted mucus. This study indicates that production of mucus by kleptoplast-bearing sea slugs is supported by photosynthesis, confirming the biological relevance of kleptoplasty to the fitness of these peculiar mollusks. Abstract A handful of sea slugs of the order Sacoglossa are able to steal chloroplasts—kleptoplasts—from their algal food sources and maintain them functionally for periods ranging from several weeks to a few months. In this study, we investigated the role of kleptoplast photosynthesis on mucus production by the tropical sea slug Elysia crispata. Animals reared for 5 weeks in quasi dark (5 μmol photons m−2 s−1) showed similar growth to those under regular light (60–90 μmol photons m−2 s−1), showing that kleptoplast photosynthesis was not relevant for growth when sea slugs were fed ad libitum. However, when subjected to short-term desiccation stress, animals reared under regular light produced significantly more mucus. Furthermore, the carbohydrate content of secreted mucus was significantly lower in slugs limited in the photosynthetic activity of their kleptoplasts by quasi-dark conditions. This study indicates that photosynthesis supports the synthesis of protective mucus in kleptoplast-bearing sea slugs.

Project description:Photosynthetic organelles offer attractive features for engineering small molecule bioproduction by their ability to convert solar energy into chemical energy required for metabolism. The possibility to couple biochemical production directly to photosynthetic assimilation as a source of energy and substrates has intrigued metabolic engineers. Specifically, the chemical diversity found in plants often relies on cytochrome P450-mediated hydroxylations that depend on reductant supply for catalysis and which often lead to metabolic bottlenecks for heterologous production of complex molecules. By directing P450 enzymes to plant chloroplasts one can elegantly deal with such redox prerequisites. In this study, we explore the capacity of the plant photosynthetic machinery to drive P450-dependent formation of the indigo precursor indoxyl-β-D-glucoside (indican) by targeting an engineered indican biosynthetic pathway to tobacco (Nicotiana benthamiana) chloroplasts. We show that both native and engineered variants belonging to the human CYP2 family are catalytically active in chloroplasts when driven by photosynthetic reducing power and optimize construct designs to improve productivity. However, while increasing supply of tryptophan leads to an increase in indole accumulation, it does not improve indican productivity, suggesting that P450 activity limits overall productivity. Co-expression of different redox partners also does not improve productivity, indicating that supply of reducing power is not a bottleneck. Finally, in vitro kinetic measurements showed that the different redox partners were efficiently reduced by photosystem I but plant ferredoxin provided the highest light-dependent P450 activity. This study demonstrates the inherent ability of photosynthesis to support P450-dependent metabolic pathways. Plants and photosynthetic microbes are therefore uniquely suited for engineering P450-dependent metabolic pathways regardless of enzyme origin. Our findings have implications for metabolic engineering in photosynthetic hosts for production of high-value chemicals or drug metabolites for pharmacological studies.

Dataset Information

Photosynthesis in a different light: spectro-microscopy for in vivo characterization of chloroplasts.

Publications

Photosynthesis in a different light: spectro-microscopy for in vivo characterization of chloroplasts.

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