High light-induced changes in whole-cell proteomic profile and its correlation with the organization of thylakoid super-complex in cyclic electron transport mutants of Chlamydomonas reinhardtii

Mild osmotic stress offers photoprotection in Chlamydomonas reinhardtii under high light

The exposure of autotrophs to high light intensities significantly impacts their photosynthetic performance. When combined with unpredictable climate changes, the lethality of these effects is exacerbated and, often surpassing the organisms' threshold for tolerance. In this regard, our study centres on examining the mitigating effects of mild osmotic stress induced by 2% Polyethylene Glycol (PEG) in conjunction with high-light conditions, using Chlamydomonas reinhardtii as a model system. Cells were cultivated under low PEG-induced osmotic stress at various light intensities, and their responses were analyzed through biochemical and biophysical approaches. Remarkably, cells grown under lower PEG concentrations exhibited superior growth, increased biomass, and enhanced photosynthetic efficiency under high light compared to non-PEG-treated cells. Surprisingly, their non-photochemical quenching (NPQ) levels were lower, indicating the operation of a distinct photoprotective mechanism in PEG-grown samples. The PEG-grown cells demonstrated higher chlorophyll content but lower carotenoid content, supporting the NPQ data. Circular dichroism analysis suggested that the macro-organization of super-complexes was minimally disrupted in PEG-grown samples, even under high light. This was further supported by Blue native PAGE, which showed greater stability of the super-complexes in PEG-grown cells, implying heightened stability in pigment-protein interactions. Immunoblot analysis revealed minimal differences in core reaction center proteins between PEG-grown and non-PEG cells. Notably, this protective mechanism was absent in the cell wall-deficient mutant CC503. We propose that the partial photoprotection observed is attributed to the PEG shielding the cell wall. This result holds promise for enhancing algal biomass production under natural environmental conditions influenced by fluctuating light intensity.

International conference on "Photosynthesis and Hydrogen Energy Research for Sustainability-2023": in honor of Robert Blankenship, Győző Garab, Michael Grätzel, Norman Hüner and Gunnar Öquist

The 11th International Photosynthesis Conference on Hydrogen Energy Research and Sustainability 2023 was organized in honor of Robert Blankenship, Győző Garab, Michael Grätzel, Norman Hüner, and Gunnar Öquist, in Istanbul, Türkiye at Bahçeşehir University Future Campus from 03 to 09 July 2023. It was jointly supported by the International Society of Photosynthesis Research (ISPR) and the International Association for Hydrogen Energy (IAHE). In this article we provide brief details of the conference, its events, keynote speakers, and the scientific contribution of scientists honored at this conference. Further, we also describe the participation of young researchers, their talks, and their awards.

Exploring LHCSR3 expression and its role in Chlamydomonas reinhardtii under osmotic stress: Implications for non-photochemical quenching mechanism

Plants have a protective mechanism called non-photochemical quenching to prevent damage caused by excessive sunlight. A critical component of this mechanism is energy-dependent quenching (qE). In Chlamydomonas reinhardtii, the protein expression called light-harvesting complex stress-related protein 3 (LHCSR3) is crucial for the qE mechanism. LHCSR3 expression is observed in various conditions that result in photooxidation, such as exposure to high light or nutrient deprivation, where the amount of captured light surpasses the maximum photosynthetic capacity. Although the role of LHCSR3 has been extensively studied under high light (HL) conditions, its function during nutrient starvation remains unclear. In this study, we demonstrate that LHCSR3 expression can occur under light intensities below saturation without triggering qE, particularly when nutrients are limited. To investigate this, we cultivated C. reinhardtii cells under osmotic stress, which replicates conditions of nutrient scarcity. Furthermore, we examined the photosynthetic membrane complexes of wild-type (WT) and npq4 mutant strains grown under osmotic stress. Our analysis revealed that LHCSR3 expression might modify the interaction between the photosystem II core and its peripheral light-harvesting complex II antennae. This alteration could potentially impede the transfer of excitation energy from the antenna to the reaction center.

An oral toxicity assessment of a mosquito larvicidal transgenic algae (Chlamydomonas reinhardtii) using adult Zebrafish and its embryos

Mosquito-borne diseases pose a global health threat, with pathogens like Malaria, Dengue fever, and others transmitted by mosquitoes. Our study focuses on evaluating the toxicity of genetically engineered mosquito larvicidal algae (Chlamydomonas reinhardtii) to non-target organisms, specifically Zebrafish. We conducted a 90-day experiment, feeding Zebrafish different combinations of larvicidal algae and commercial fish feed. Statistical analysis revealed no significant differences in mortality, allergenicity, or moribundity among groups. Hematology, molecular analysis, and necropsy showed no physiological differences. Our findings indicate that the transgenic algae (TN72.cry11Ba) had no adverse effects on adult Zebrafish or their larvae. This study confirmed the safety of algae on non-target organisms, such as zebrafish.

Key Proteomics Tools for Fundamental and Applied Microalgal Research

Microscopic, photosynthetic prokaryotes and eukaryotes, collectively referred to as microalgae, are widely studied to improve our understanding of key metabolic pathways (e.g., photosynthesis) and for the development of biotechnological applications. Omics technologies, which are now common tools in biological research, have been shown to be critical in microalgal research. In the past decade, significant technological advancements have allowed omics technologies to become more affordable and efficient, with huge datasets being generated. In particular, where studies focused on a single or few proteins decades ago, it is now possible to study the whole proteome of a microalgae. The development of mass spectrometry-based methods has provided this leap forward with the high-throughput identification and quantification of proteins. This review specifically provides an overview of the use of proteomics in fundamental (e.g., photosynthesis) and applied (e.g., lipid production for biofuel) microalgal research, and presents future research directions in this field.

TMT-Based Proteomics Analysis of Senescent Nucleus Pulposus from Patients with Intervertebral Disc Degeneration

Lower back pain, a leading cause of disability worldwide, is associated with intervertebral disc degeneration (IDD) in approximately 40% of cases. Although nucleus pulposus (NP) cell senescence is a major contributor to IDD, the underlying mechanisms remain unclear. We collected NP samples from IDD patients who had undergone spinal surgery. Healthy and senescent NP tissues (n = 3) were screened using the Pfirrmann grading system combined with immunohistochemistry, as well as hematoxylin and eosin, Safranin O, Alcian blue, and Masson staining. Differentially expressed proteins (DEPs) were identified using quantitative TMT-based proteomics technology. Bioinformatics analyses included gene ontology (GO) annotation, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, and protein-protein interaction (PPI) analyses. In addition, immunofluorescence was used to verify protein expression. In total, 301 DEPs were identified in senescent NP tissues, including 92 upregulated and 209 downregulated proteins. In GO, DEPs were primarily associated with NF-kappaB transcription factor, extracellular regions, cellular protein metabolic processes, and post-translational protein modification. The enriched KEGG pathways included TGF-β, Wnt, RAP1, interleukin-17, extracellular matrix-receptor adhesion, and PI3K/Akt signaling pathways. PPI analysis demonstrated interactions between multiple proteins. Finally, immunofluorescence verified the expressions of MMP3, LUM, TIMP1, and CDC42 in senescent NP cells. Our study provides valuable insights into the mechanisms underlying senescent NP tissues in IDD patients. DEPs provide a basis for further investigation of the effects of senescent factors on IDD.