Dataset Information

Engineering astaxanthin accumulation reduces photoinhibition and increases biomass productivity under high light in Chlamydomonas reinhardtii.

ABSTRACT:

Background

Astaxanthin is a highly valuable ketocarotenoid with strong antioxidative activity and is natively accumulated upon environmental stress exposure in selected microorganisms. Green microalgae are photosynthetic, unicellular organisms cultivated in artificial systems to produce biomass and industrially relevant bioproducts. While light is required for photosynthesis, fueling carbon fixation processes, application of high irradiance causes photoinhibition and limits biomass productivity.

Results

Here, we demonstrate that engineered astaxanthin accumulation in the green alga Chlamydomonas reinhardtii conferred high light tolerance, reduced photoinhibition and improved biomass productivity at high irradiances, likely due to strong antioxidant properties of constitutively accumulating astaxanthin. In competitive co-cultivation experiments, astaxanthin-rich Chlamydomonas reinhardtii outcompeted its corresponding parental background strain and even the fast-growing green alga Chlorella vulgaris.

Conclusions

Metabolic engineering inducing astaxanthin and ketocarotenoids accumulation caused improved high light tolerance and increased biomass productivity in the model species for microalgae Chlamydomonas reinhardtii. Thus, engineering microalgal pigment composition represents a powerful strategy to improve biomass productivities in customized photobioreactors setups. Moreover, engineered astaxanthin accumulation in selected strains could be proposed as a novel strategy to outperform growth of other competing microalgal strains.

SUBMITTER: Cazzaniga S

PROVIDER: S-EPMC9277849 | biostudies-literature | 2022 Jul

REPOSITORIES: biostudies-literature

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Publications

Engineering astaxanthin accumulation reduces photoinhibition and increases biomass productivity under high light in Chlamydomonas reinhardtii.

Cazzaniga Stefano S Perozeni Federico F Baier Thomas T Ballottari Matteo M

Biotechnology for biofuels and bioproducts 20220711 1

<h4>Background</h4>Astaxanthin is a highly valuable ketocarotenoid with strong antioxidative activity and is natively accumulated upon environmental stress exposure in selected microorganisms. Green microalgae are photosynthetic, unicellular organisms cultivated in artificial systems to produce biomass and industrially relevant bioproducts. While light is required for photosynthesis, fueling carbon fixation processes, application of high irradiance causes photoinhibition and limits biomass produ ...[more]

PMID: 35820961

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Project description:Interest in exploiting algae as a biofuel source and the role of nutrient deficiency in inducing triacylglyceride (TAG) accumulation in cells necessitates a strategy to efficiently formulate species-specific culture media that can be easily manipulated. Using the reference organism Chlamydomonas reinhardtii, we tested the hypothesis that modeling trace element supplements on the ionomes of cells would result in optimized cell growth. We characterized the ionomes of multiple wild-type Chlamydomonas strains in various culture conditions and developed a revised trace element solution to parallel our measurements. Comparison of cells growing in the revised supplement versus a traditional trace element solution revealed faster growth rates and higher maximum cell densities with the revised recipe. RNA-seq analysis of cultures growing in the traditional versus revised medium suggest that the variation in transcriptomes was smaller than that found between laboratories using the same supplement. Visual observation did not reveal defects in cell motility or mating efficiency. Ni2+-inducible expression from the CYC6 promoter remained a useful tool, albeit with an increased amount of Ni2+ supplementation due to the introduction of an EDTA buffer system in the revised medium. Equilibrium modeling of the revised supplement predicts less metal precipitation in the revised medium. Other advantages include more facile preparation of trace element stock solutions that can readily be adapted for deficiency studies, a reduction in total chemical use, a more consistent batch-to-batch formulation, and long-term stability (up to 5 years). Under the new growth regime, we analyzed cells growing under different macro- and micronutrient-deficiencies. In N and S deficiency, cells accumulate TAG as well in the new medium as previously demonstrated. Fe and Zn deficiency also induced TAG accumulation as suggested by Nile Red and Bodipy staining. This ionomic approach can be used to efficiently optimize culturing conditions for other algal species to improve growth and assay cell physiology.

Project description:BACKGROUND:Proteasomes remove regulatory proteins in eukaryotic cells, and control a variety of plant processes. Proteasomes are localized to the cytosol and nuclear, but their role in plant biology has recently been extended to chloroplasts, where it regulates TOC complex. This is turn controls the import of nuclear-encoded chloroplastic proteins, which remodels the chloroplast proteome and facilitates proper developmental transitions. Proteasomal regulation of the TOC complex also alleviates stressors that generate reactive oxygen species. These recent advances motivated us to determine if proteasome inhibition rapidly alters photosynthetic processes stemming from photoinhibition induced by high light. RESULTS:The short-term effects of proteasome inhibition on photosystem II during light stress was measured in Chlamydomonas reinhardtii, which allowed the dual monitoring of both chlorophyll fluorescence and cell viability. After 48 h at low light, proteasome inhibition did not affect viability or photochemistiry, but decreased cell concentration and increased cell volume. Two hours of high light stress impaired the efficiency of photosystem II in proteasome-inhibited cells, as determined by a decrease in Fv/Fm and the electron transport rate. Elevated photoinhibition in proteasome inhibited cells was not caused by a decrease in cell viability or chlorophyll content. Recovery from photoinhibition was attenuated in MG132-treated cells, and suppressed growth of a reestablished culture. Proteasome inhibition decreased de novo protein synthesis, which possibly constrained the ability to remodel the plastid proteome, and thus hampering the ability to adjust to high light stress. CONCLUSION:The proteasome is implicated in protecting photosystem II from photoinhibition. In addition to high light stress, other stressors- including metals, drought, and salt- are also known to generate reactive oxygen species localized to the chloroplast. Therefore, proteasome maintenance in plants may help protect photosynthesis during abiotic stress, which could increase crop yield during adverse conditions.

Dataset Information

Engineering astaxanthin accumulation reduces photoinhibition and increases biomass productivity under high light in Chlamydomonas reinhardtii.

Background

Results

Conclusions

Publications

Engineering astaxanthin accumulation reduces photoinhibition and increases biomass productivity under high light in Chlamydomonas reinhardtii.

Similar Datasets

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