Transcriptome dynamics and hub genes of green alga Nannochloris sp. JB17 under NaHCO3 stress

Review of biological algal fertilizer technology: Alleviating salinization, sequestering carbon, and improving crop productivity

Periphyton-based biofertilizer have a high potential for soil remediation, particularly for controlling soil salinization. This global environmental problem leads to low soil utilization and insufficient crop yields. Efficient and sustainable methods of managing saline soils are needed to reduce salinization and improve soil fertility and crop quality. Traditional methods such as physical mulching and chemical amendments, while improving soil conditions, exhibit limited effectiveness and may damage soil structure. This study aims to evaluate the feasibility of algae-based fertilizers in remediating saline-alkali soils and improving crop performance. The review delves into the and application prospects of algae-based fertilizers, highlighting their potential from both sustainable development and economic perspectives. It further advocates integrating other emerging technologies with the production and application of algae-based fertilizers to address the increasingly severe challenges posed by degraded soil resources and environmental instability. The review found that algal fertilizers are more environmentally friendly than traditional chemical fertilizers but are not inferior in function. This approach offers more efficient and sustainable solutions for managing saline-alkaline soils and effectively achieves sustainable agricultural production. Furthermore, it is necessary to conduct experimental research and monitoring evaluations of algal fertilizers to formulate scientific and rational fertilization plans to meet the increasingly serious challenges facing soil resources and unstable environments. The findings of this study will provide theoretical and technical support for using algae biofertilizers for soil remediation, improving crop quality and sequestering carbon.

Nannochloris sp. JB17 as a Potential Microalga for Carbon Capture and Utilization Bio-Systems: Growth and Biochemical Composition Under High Bicarbonate Concentrations in Fresh and Sea Water

Nannochloris sp. JB17 has been identified as an interesting microalgal species that can tolerate high salinity and high bicarbonate concentrations. In this study, Nannochloris sp. JB17 was long-term adapted to increased bicarbonate concentrations (10-60 g NaHCO3 per L) in fresh or sea-water-based growing media. This study aimed to evaluate its growth performance and biochemical composition under different cultivation conditions. The highest biomass production (1.24-1.3 g/L) achieved in the study was obtained in fresh water media supplemented with 40 g/L and 60 g/L NaHCO3, respectively. Total protein content fluctuated at similar levels among the different treatments (32.4-38.5%), displaying good essential amino acids indices of 0.85-1.02, but with low in vitro protein digestibility (15-20%) rates. Total lipids did not show any significant alteration among the different NaHCO3 concentrations in both fresh and sea water (12.6-13.3%) but at increased sodium strength, a significant increase in unsaturated lipids and in particular a-linolenic acid (C18:3) and linoleic acid (C18:2) was observed. Carbohydrate content also ranged at very similar levels among the cultures (26-30.9%). The main fraction of carbohydrates was in the type of neutral sugars ranging from around 72% to 80% (of total carbohydrates), while uronic acids were in negligible amounts. Moreover, Nannochloris sp. showed that it contained around 8-9% sulfated polysaccharides. Since the microalgae display good growth patterns at high bicarbonate concentrations, they could be a potential species for microalgal-based carbon capture and utilization systems.

Microalgae biofuels: illuminating the path to a sustainable future amidst challenges and opportunities

The development of microalgal biofuels is of significant importance in advancing the energy transition, alleviating food pressure, preserving the natural environment, and addressing climate change. Numerous countries and regions across the globe have conducted extensive research and strategic planning on microalgal bioenergy, investing significant funds and manpower into this field. However, the microalgae biofuel industry has faced a downturn due to the constraints of high costs. In the past decade, with the development of new strains, technologies, and equipment, the feasibility of large-scale production of microalgae biofuel should be re-evaluated. Here, we have gathered research results from the past decade regarding microalgae biofuel production, providing insights into the opportunities and challenges faced by this industry from the perspectives of microalgae selection, modification, and cultivation. In this review, we suggest that highly adaptable microalgae are the preferred choice for large-scale biofuel production, especially strains that can utilize high concentrations of inorganic carbon sources and possess stress resistance. The use of omics technologies and genetic editing has greatly enhanced lipid accumulation in microalgae. However, the associated risks have constrained the feasibility of large-scale outdoor cultivation. Therefore, the relatively controllable cultivation method of photobioreactors (PBRs) has made it the mainstream approach for microalgae biofuel production. Moreover, adjusting the performance and parameters of PBRs can also enhance lipid accumulation in microalgae. In the future, given the relentless escalation in demand for sustainable energy sources, microalgae biofuels should be deemed a pivotal constituent of national energy planning, particularly in the case of China. The advancement of synthetic biology helps reduce the risks associated with genetically modified (GM) microalgae and enhances the economic viability of their biofuel production.

Exploring cell aggregation as a defense strategy against perchlorate stress in Chlamydomonas reinhardtii through multi-omics analysis

Perchlorate (ClO4-) is a type of novel, widely distributed, and persistent inorganic pollutant. However, the impacts of perchlorate on freshwater algae remain unclear. In this study, the response and defense mechanisms of microalgae (Chlamydomonas reinhardtii) under perchlorate stress were investigated by integrating physiological and biochemical monitoring, transcriptomics, and metabolomics. Weighted gene co-expression network analysis (WGCNA) of transcriptome data was used to analyze the relationship between genes and phenotype and screen the key pathways. C. reinhardtii exhibited aggregate behavior when exposed to 100- and 200-mM perchlorate but was restored to its unicellular lifestyle when transferred to fresh medium. WGCNA results found that the "carbohydrate metabolism" and "lipid metabolism" pathways were closely related to cell aggregation phenotype. The differential expression genes (DEGs) and differentially accumulated metabolites (DAMs) of these pathways were upregulated, indicating that the lipid and carbohydrate metabolisms were enhanced in aggregated cells. Additionally, most genes and metabolites related to phytohormone abscisic acid (ABA) biosynthesis and the mitogen-activated protein kinase (MAPK) signaling pathway were significantly upregulated, indicating their crucial roles in the signal transmission of aggregated cells. Meanwhile, in aggregated cells, extracellular polymeric substances (EPS) and lipid contents increased, photosynthesis activity decreased, and the antioxidant system was activated. These characteristics contributed to C. reinhardtii's improved resistance to perchlorate stress. Above results demonstrated that cell aggregation behavior was the principal defense strategy of C. reinhardtii against perchlorate. Overall, this study sheds new light on the impact mechanisms of perchlorate to aquatic microalgae and provides multi-omics insights into the research of multicellular-like aggregation as an adaptation strategy to abiotic stress. These results are beneficial for assessing the risk of perchlorate in aquatic environments.

Physiological responses of marine Chlorella sp. exposed to environmental levels of triphenyltin

Triphenyltin (TPT) is a herbicide and antifouling agent that has been widely used. After TPT flows into water bodies, it will cause toxic effects on marine life. We evaluated the effect of environmental concentration level (0, 10, 100, and 200 ng/L) on the cell density, antioxidant capability, and photosynthesis-related genes in the marine Chlorella sp. The results showed that 10 and 100 ng/L TPT can promote the growth of marine Chlorella sp., 200 ng/L TPT can inhibit the growth of marine Chlorella sp., and the TPT toxicity was accumulative. The chlorophyll composition changed. The content of chlorophyll a in 100 ng/L and 200 ng/L groups was significantly higher than that in the control group (p < 0.05) in 13 days. The content of chlorophyll b in the 100 ng/L and 200 ng/L groups in 1 day and 13 days was significantly different from that in the control group (p < 0.05). The content of total chlorophyll in the 100 ng/L and 200 ng/L groups in 13 days was higher than that in the control group (p < 0.05). The 200 ng/L group began to suffer oxidative damage on the 12th day, and the pigment protein complex responded to oxidative damage through self-feedback regulation. On the 18th day, chld, cao, psy, rbcS, and rbcL genes were downregulated, and psbA gene was upregulated in the 10 ng/L and 100 ng/L groups, which may be a feedback regulation of self-oxidative damage. This paper analyzed toxicity of environmental levels of TPT to marine Chlorella sp., which provided new data support for the comprehensive evaluation of its marine ecological toxicity.

Identification of Potential Pathways of Morella cerifera Seedlings in Response to Alkali Stress via Transcriptomic Analysis

Alkali stress, a type of abiotic stress, severely inhibits plant growth. Only a few studies have investigated the mechanism underlying the transcriptional-level response of Morella cerifera to saline-alkali stress. Based on RNA-seq technology, gene expression differences in the fibrous roots of M. cerifera seedlings exposed to low- and high-concentration alkali stress (LAS and HAS, respectively) were investigated, and the corresponding 1312 and 1532 alkali stress-responsive genes were identified, respectively. According to gene set enrichment analysis, 65 gene sets were significantly enriched. Of these, 24 gene sets were shared by both treatment groups. LAS and HAS treatment groups exhibited 9 (all downregulated) and 32 (23 downregulated) unique gene sets, respectively. The differential gene sets mainly included those involved in trehalose biosynthesis and metabolism, phospholipid translocation, and lignin catabolism. Kyoto Encyclopedia of Genes and Genomes pathway analysis revealed that M. cerifera seedlings were specifically enriched in stilbenoid, diarylheptanoid, and gingerol biosynthesis; phenylalanine, tyrosine, and tryptophan biosynthesis; and sesquiterpenoid and triterpenoid biosynthesis. Moreover, the related genes involved in hormone signaling pathways and transcription factors were determined through a localization analysis of core abiotic stress pathways. These genes and their molecular mechanisms will be the focus of future research.

A comprehensive review on carbon source effect of microalgae lipid accumulation for biofuel production

Energy is a major driving force for the economic development. Due to the scarcity of fossil fuels and negative impact on the environment, it is important to develop renewable and sustainable energy sources for humankind. Microalgae as the primary feedstock for biodiesel has shown great application potential. However, lipid yield from microalgae is limited by the upstream cost, which restrain the realization of large-scale biofuel production. The modification of lipid-rich microalgae cell has become the focus over the last few decades to improve the lipid content and productivity of microalgae. Carbon is a vital nutrient that regulates the growth and metabolism of microalgae. Different carbon sources are assimilated by microalgae cells via different pathways. Inorganic carbon sources are mainly used through the CO₂-concentrating mechanisms (CCMs), while organic carbon sources are absorbed by microalgae mainly through the Pentose Phosphate (PPP) Pathway and the Embden-Meyerhof-Pranas (EMP) pathway. Therefore, the addition of carbon source has a significant impact on the production of microalgae biomass and lipid accumulation. In this paper, mechanisms of lipid synthesis and carbon uptake of microalgae were introduced, and the effects of different carbon conditions (types, concentrations, and addition methods) on lipid accumulation in microalgal biomass production and biodiesel production were comprehensively discussed. This review also highlights the recent advances in microalgae lipid cultivation with large-scale commercialization and the development prospects of biodiesel production. Current challenges and constructive suggestions are proposed on cost-benefit concerns in large-scale production of microalgae biodiesel.

Biotinylated subunit of 3-methylcrotonyl-CoA carboxylase encoding gene (AtMCCA) participating in Arabidopsis resistance to carbonate Stress by transcriptome analysis

Soil salinization is a major factor impacting modern agricultural production, and alkaline soils contain large amounts of NaHCO₃. Therefore, understanding plant tolerance to high levels of NaHCO₃ is essential. In this study, a transcriptome analysis of shoot and root tissues of wild-type Arabidopsis thaliana was conducted at 0, 4, 12, 24 and 48 h after exposure to a 3 mM NaHCO₃ stress. We focused on differentially expressed genes (DEGs) in roots identified in the early stages (4 h and 12 h) of the NaHCO₃ stress response that were enriched in GO term, carboxylic acid metabolic process, and utilize HCO₃^-. Six genes were identified that exhibited similar expression patterns in both the RNA-seq and qRT-PCR data. We also characterized the phenotypic response of AtMCCA-overexpressing plants to carbonate stress, and found that the ability of AtMCCA-overexpressing plants to tolerate carbonate stress was enhanced by the addition of biotin to the growth medium.