Biology subjects

Cazzaniga, S.

Publications and source records attributed to Cazzaniga, S..

8 recordsLinked to original sources

bioRxiv2026

Agricultural digestate ultrafiltrate outperforms synthetic media for microalgal biomass production while enabling biostimulant generation

Livestock digestate ultrafiltrate (UF), obtained through membrane treatment of anaerobic digestate, is a nutrient-rich stream whose valorization remains largely unexplored. By removing suspended solids while retaining dissolved nutrients, ultrafiltration reduces turbidity and overcomes major limitations associated with using digestate for microalgal cultivation. This study evaluated UF as a nutrient source for Chlorella sorokiniana and Nannochloropsis oceanica, coupling ammonium recovery and biomass production with biomass valorization as a plant biostimulant. Given the high ammonium content of UF, ammonium tolerance was assessed in both species using ammonium bicarbonate as the nitrogen source. Increasing UF concentrations were then tested in laboratory photobioreactors and compared with synthetic media. Biomass productivity, nutrient removal, biomass composition, and biostimulant activity were evaluated. Both species tolerated ammonium-rich conditions and grew efficiently in UF-based media. UF significantly outperformed synthetic media, increasing biomass accumulation by up to 104% in N. oceanica and 133% in C. sorokiniana, while ammonium removal exceeded 99% and 98%, respectively. C. sorokiniana maintained high productivity when UF was diluted exclusively with water, indicating that UF supplied most nutrients required for growth. The enhanced productivity could not be explained solely by ammonium availability, suggesting a contribution from the complex nutrient composition retained during ultrafiltration. UF-derived biomass exhibited biostimulant activity, promoting tomato root development and increasing root and shoot biomass under reduced nitrogen availability. Digestate-derived UF therefore acts as both an efficient nutrient-recovery stream and a growth-promoting microalgal medium, enabling the conversion of membrane-treated digestate into biostimulant biomass within a circular biorefinery framework.

bioengineering↗

bioRxiv2026

Photoprotection comes at a cost: non-photochemical quenching shapes growthproductivity trade-offs in Haematococcus lacustris

Non-photochemical quenching (NPQ) dissipates excess absorbed light energy and protects photosynthetic organisms from photodamage, but its role in regulating the balance between growth, stress tolerance and astaxanthin accumulation in Haematococcus lacustris remains unclear. Here, we investigated how enhanced NPQ affects photosynthetic performance, stress-induced differentiation, and productivity in this astaxanthin-producing microalga. We isolated and characterized an NPQ-enhanced mutant line, A116, using cultivation assays under different stress conditions, analysis of photosynthetic parameters, pigment profiling, and whole-genome resequencing. A116 displayed stronger and faster NPQ induction, driven by increased LHCSR accumulation, resulting in decreased photosynthetic electron transport and lower photochemical efficiency under moderate-to-high light. Enhanced NPQ delayed the transition to astaxanthin-rich cysts under high light, allowing greater biomass accumulation under CO2-limiting conditions. However, under high CO2 availability, where carbon fixation relieved excitation pressure supporting efficient photosynthesis, the enhanced NPQ phenotype reduced growth and astaxanthin productivity compared with the wild type. These results show that NPQ modulates a context-dependent trade-off between photoprotection and productivity in Haematococcus lacustris. Increased energy dissipation can improve high-light tolerance under carbon limitation, but becomes detrimental when absorbed light can be efficiently used for carbon assimilation. Thus, optimal algal productivity requires tuning photoprotective capacity to environmental conditions rather than maximizing NPQ.

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↗

bioRxiv2021

Initiation of organ maturation and fruit ripening in grapevine is controlled by the CARPO-NAC transcription factor

Grapevine is a woody temperate perennial plant and one of the most important fruit crops with global relevance in both the fresh fruit and winemaking industries. Unfortunately, global warming is affecting viticulture by altering developmental transitions and fruit maturation processes. In this context, uncovering the molecular mechanisms controlling the onset and progression of ripening could prove essential to maintain high-quality grapes and wines. Through a deep inspection of previously published transcriptomic data we identified the NAC family member VviCARPO (Controlled Adjustment of Ripening and maturation of Plant Organs) as a key regulator of grapevine maturation whose induction precedes the expression of well-known ripening associated genes. We explored VviCARPO binding landscapes through DAP-seq and overlapped its bound genes with transcriptomics datasets from stable and transient VviCARPO overexpressing grapevine plants to define a set of high-confidence targets. Among these, we identified key molecular ripening markers. Physiological, metabolic and promoter activation analyses showed that VviCARPO induces chlorophyll degradation and anthocyanin accumulation through the up-regulation of VviSGR1 and VviMYBA1, respectively, with the latter being up-regulated through a VviCARPO-VviNAC03 regulatory complex. Despite showing a closer phylogenetic relationship to senescent-related AtNAP homologues, VviCARPO complemented the nor mutant phenotype in tomato, suggesting it may have acquired a dual role as an orchestrator of both ripening- and senescence-related processes. Our data supports CARPO as a master regulator of the grapevine vegetative-to-mature phase organ transition and therefore an essential target for insuring fruit quality and environmental resilience. SIGNIFICANT STATEMENTCARPO is a grape NAC transcription factor central to fruit ripening and tissue senescence. This regulator influences multiple biological pathways common to both processes including cell wall metabolism, chlorophyll degradation, pigment production and hormone synthesis/signaling through regulation of their key genes. As various external stresses and changing climatic conditions influence vegetative growth and berry ripening, CARPO could prove a useful genetic and breeding target towards maintaining necessary crop performance and fruit-quality characteristics.

plant biology↗

bioRxiv2021

CO2 supply modulates lipid remodelling, photosynthetic and respiratory activities in Chlorella species

Microalgae represent potential solutions to reduce the atmospheric CO2 level through photosynthesis. To boost CO2 fixation by microalgae it is essential to understand physiologic and metabolic responses at the base of CO2 assimilation and carbon flow. In this work two Trebouxiophyceae species, Chlorella sorokiniana and Chlorella vulgaris, were investigated for their metabolic responses to high and low CO2 (air level) availability. High CO2 availability resulted in an increase in biomass accumulation in both species but with a different chloroplast and mitochondrial responses. In C. sorokiniana we observed increased polar lipids and protein amount and a balanced NADPH redox state and a similar total respiration in the two conditions analysed. In contrast, in C. vulgaris high CO2 level caused an increase in TAG accumulation and a higher NADPH consumption suggesting a CO2 dependent increase of reducing power consumption in the chloroplast, which in turn influences the redox state of the mitochondria by lowering total dark respiration. Several rearrangements of the photosynthetic machinery were observed in both species, which differ from those described for the model organism Chlamydomonas reinhardtii. In the case of C. reinhardtii, adaptation of the photosynthetic apparatus to different CO2 availability relies on the translational repressor NAB1. NAB1 homologous protein could be identified only in C. vulgaris but lacked the regulation mechanisms previously described in C. reinhardtii. These findings highlight that the acclimation strategies to cope with a fluctuating inorganic carbon supply are diverse among green microalgae and point to new biotechnological strategies to boost CO2 fixation. One sentence summaryHigh/low CO2 availability induces cell responses as lipids remodelling, adaptations of the photosynthetic apparatus and modulation of mitochondrial respiration not conserved among green algae

plant biology↗

bioRxiv2021

A synthetic switch based on orange carotenoid protein to control blue light responses in chloroplasts

ABSTRACTSynthetic biology approaches to engineer light-responsive system are widely used, but their applications in plants are still limited, due to the interference with endogenous photoreceptors. Cyanobacteria, such as Synechocystis spp., possess a soluble carotenoid associated protein named Orange Carotenoid binding Protein (OCP) that, when activated by blue-green light, undergoes reversible conformational changes that enable photoprotection of the phycobilisomes. Exploiting this system, we developed a new chloroplast-localized synthetic photoswitch based on a photoreceptor-associated protein-fragment complementation assay (PCA). Since Arabidopsis thaliana does not possess the prosthetic group needed for the assembly of the OCP2 protein, we implemented the carotenoid biosynthetic pathway with a bacterial {beta}-carotene ketolase enzyme (crtW), to generate keto-carotenoids producing plants. The novel photoswitch was tested and characterized in Arabidopsis protoplasts with experiments aimed to uncover its regulation by light intensity, wavelength, and its conversion dynamics. We believe that this pioneer study establishes the basis for future implementation of plastid optogenetics to regulate organelle responses, such as gene transcription or enzymatic activity, upon exposure to specific light spectra. One-sentence summaryInspired by the light-driven conformational transitions of orange carotenoid proteins of cyanobacteria, we generated a molecular device able to switch its dimeric state in response to blue light.

synthetic biology↗

bioRxiv2020

Pharmacological tuning of microRNA in FAP-derived Extracellular Vesicles by HDAC inhibitors promotes regeneration and reduces fibrosis in dystrophic muscles.

Functional interactions between cellular components of the muscle stem cell (MuSC) niche regulate the regenerative ability of skeletal muscles in physiological and pathological conditions; however, the identity of the mediators of these interactions remains largely unknown. We show here that fibro-adipogenic progenitor (FAP)-derived Extracellular Vesicles (EVs) mediate microRNA transfer to MuSCs, and that exposure of dystrophic FAPs to HDAC inhibitors (HDACi) increases the intra-EV levels of a subset of microRNAs (miRs), which cooperatively target biological processes of therapeutic interest, including regeneration, fibrosis and inflammation. In particular, we found that increased levels of miR206 in EVs released from FAPs of muscles from Duchenne dystrophic patients or mice (mdx) exposed to HDACi were associated with enhanced regeneration and inhibition of fibrosis of dystrophic muscles. Consistently, EVs from HDACi-treated dystrophic FAPs could stimulated MuSC activation and expansion ex vivo, and promoted regeneration, while inhibiting fibrosis and inflammation of dystrophic muscles, upon intramuscular transplantation, in vivo. These data reveal a potential for pharmacological modulation of FAP-derived EVs content as novel strategy for focal therapeutic interventions in Duchenne Muscular Dystrophy (DMD) and possibly other muscular diseases. Brief SummaryExtracellular Vesicles from HDACi-treated dystrophic FAPs promote regeneration, while inhibiting fibrosis and inflammation of dystrophic muscles

cell 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↗