Biology subjects

Perozeni, F.

Publications and source records attributed to Perozeni, F..

3 recordsLinked to original sources

bioRxiv2025

Heterologous expression of the cyanobacterial fructose-1,6-/sedoheptulose-1,7-bisphosphatase in Chlamydomonas reinhardtii causes increased cell size and biomass productivity in mixotrophic conditions

The Calvin-Benson-Bassham (CBB) cycle is the metabolic pathway responsible for CO assimilation in oxygenic photosynthetic organisms. Two key rate-limiting steps in this cycle are catalyzed by the enzymes fructose-1,6-bisphosphatase (FBPase) and sedoheptulose-1,7-bisphosphatase (SBPase), making them promising targets for genetic enhancement to improve carbon fixation. A potential strategy involves overexpressing a cyanobacterial dual-function FBP/SBPase, which catalyzes both reactionsOverexpression of this enzyme in tobacco plants or in other plants led to an increase in growth rate and biomass accumulation. Here, the overexpression of the same enzyme was achieved in Chlamydomonas reinhardtii. The recombinant cyanobacterial FBP/SBPase isolated from C. reinhardtii exhibited the expected catalytic activity, being Mg2+ dependent and strongly activated in the presence of a reducing agent. The FBP/SBPase expressing lines exhibited an increased photosynthetic activity at the cell level and decreased production of singlet oxygen upon exposure to high irradiances, suggesting improved capacity to manage high excitation pressure of the photosynthetic apparatus. Increased cell volume was measured in FBP/SBPase-expressing lines under different growth conditions. However, increased growth and biomass productivity were observed only in mixotrophy when light and CO2 were limiting, leading to increased starch, protein, and lipid content on a cellular basis. This phenotype caused an increased sedimentation rate in the transformant lines: the expression of FBP/SBPase enzyme could thus be considered as a strategy to improve the cell harvesting process. These findings provide new insights into carbon metabolism in microalgae, and could, in the future, support improved biomass accumulation, paving the way for effective domestication and industrial use.

plant biology↗

bioRxiv2022

Photosystem II monomeric antenna CP26 has a key role in Non-Photochemical Quenching in Chlamydomonas reinhardtii

O_LIThermal dissipation of the excitation energy harvested in excess, named non-photochemical quenching (NPQ), is one of the main photoprotective mechanisms evolved in oxygenic photosynthetic organisms. Here, the specific function in photoprotection and light harvesting of the monomeric Photosystem II antenna CP26, was investigated in Chlamydomonas, model organism for green algae C_LIO_LICRISPR/Cas9 genome editing and complementation strategies were applied to generate new cp26 knock-out mutants (named k6#) that differently from previous findings, did not negatively affected CP29 accumulation, allowing to compare mutants specifically deprived of CP26, CP29 or both C_LIO_LIThe absence of CP26 partially affected Photosystem II activity causing a reduced growth at low or medium light but not at high irradiances. However, the main phenotype observed in k6# mutants was a more than 70% reduction of NPQ compared to wild-type. This NPQ phenotype could be fully rescued by genetic complementation demonstrating that [~]50% of CP26 content compared to wild-type was sufficient to restore the NPQ capacity. C_LIO_LIOur findings demonstrate a pivotal role for CP26 in NPQ induction while CP29 has a crucial function for Photosystem II activity. The genetic engineering of these two proteins could be a promising strategy to regulate photosynthetic efficiency of microalgae under different light regimes. C_LI

plant biology↗

bioRxiv2019

Turning a green alga red: engineering astaxanthin biosynthesis by intragenic pseudogene revival in Chlamydomonas reinhardtii.

The green alga Chlamydomonas reinhardtii does not synthesize high-value ketocarotenoids like canthaxanthin and astaxanthin, however, a {beta}-carotene ketolase (CrBKT) can be found in its genome. CrBKT is poorly expressed, contains a long C-terminal extension not found in homologues and likely represents a pseudogene in this alga. Here, we used synthetic re-design of this gene to enable its constitutive overexpression from the nuclear genome of C. reinhardtii. Overexpression of the optimized CrBKT extended native carotenoid biosynthesis to generate ketocarotenoids in the algal host causing noticeable changes the green algal colour to a reddish-brown. We found that up to 50% of native carotenoids could be converted into astaxanthin and more than 70% into other ketocarotenoids by robust CrBKT overexpression. Modification of the carotenoid metabolism did not impair growth or biomass productivity of C. reinhardtii, even at high light intensities. Under different growth conditions, the best performing CrBKT overexpression strain was found to reach ketocarotenoid productivities up to 4.5 mg L-1 day-1. Astaxanthin productivity in engineered C. reinhardtii shown here is competitive with that reported for Haematococcus lacustris (formerly pluvialis) which is currently the main organism cultivated for industrial astaxanthin production. In addition, the extractability and bio-accessibility of these pigments was much higher in cell wall deficient C. reinhardtii than the resting cysts of H. lacustris. Engineered C. reinhardtii strains could thus be a promising alternative to natural astaxanthin producing algal strains and may open the possibility of other tailor-made pigments from this host.

plant biology↗