Xiang Gao

Scytonemin, a lipid-soluble indole-alkaloid pigment unique to cyanobacteria, is a bioactive small molecule with UV-shielding, antioxidant, and anti-inflammatory activities. Nostoc flagelliforme represents a promising strain for scytonemin biosynthesis, yet engineering to boost its yield remains challenging. Two genes encoding a histidine kinase (COO91_00772) and a response regulator (COO91_00771, ScyR) putatively constitute a two-component regulatory system governing the UV-induced biosynthesis of scytonemin. Here, we employed CRISPR/Cpf1 technology to achieve the insertion of an additional ScyR expression cassette into the N. flagelliforme genome and evaluated its effect on scytonemin yield. The engineered strain was designated Nf-psbA-ScyR, in which the ScyR gene was expressed under the PpsbA promoter. This strain exhibited a markedly enhanced accumulation of scytonemin, reaching 4.6 mg g⁻¹ dry weight under UV-B radiation after 15-day cultivation with exogenous tryptophan supplementation, representing a 1.9-fold increase compared with the MAAs-deficient (Nf-MAAs-D) strain. Upon transition from indoor UV-B exposure to outdoor solar radiation, scytonemin production further increased to 5.4 mg g⁻¹ dry weight. These findings indicate that the ScyR regulator can highly promote scytonemin biosynthesis under UV induction, providing an engineering strategy for the exploitation of N. flagelliforme.

1. With the depletion of fossil fuels and increasing concerns regarding greenhouse gas emissions, microalgae-based biodiesel has garnered substantial global interest as a sustainable alternative en...

Arrhythmogenic right ventricular cardiomyopathy (ARVC; OMIM #609040) is an inherited cardiomyopathy characterized by juvenile sudden cardiac death (SCD), with > 40% of familial cases driven by PLAKOPHILIN 2 (PKP2; OMIM #602861) mutations. This study reports a Chinese ARVC family with neonatal severe early-onset phenotype caused by novel compound heterozygous PKP2 mutations that exhibiting cosegregation with biallelic mutations (while heterozygous carriers remained asymptomatic), and aims to elucidate the synergistic pathogenic mechanisms and clinical implications. Mutations were identified via whole-genome sequencing and familial cosegregation analysis. Pathogenicity was predicted using SpliceAI and MutationTaster. MiniGene splicing assays and RT-PCR validated aberrant splicing. We analyzed subcellular protein localization by immunofluorescence microscopy and assessed protein stability via cycloheximide chase (CHX). The proband carried a maternally inherited novel splice-site variant (PKP2: c.224–3 C > G) and a paternally inherited frameshift deletion (PKP2: c.1125_1132del). Functional validation demonstrated: (a) c.224–3 C > G caused exon 2 skipping (deletion rate > 90%), generating a truncated protein (p.Asn76Trpfs*7); (b) c.1125_1132del induced frameshift (p.Phe376Alafs*8) without altering splicing. The mutant protein exhibited unchanged half-life but aberrant nuclear aggregation (immunofluorescence-confirmed). This study first confirms that compound heterozygous PKP2 mutations cause severe early-onset ARVC through biallelic inactivation: the maternal splice variant (c.224–3 C > G) truncates the protein, ablating all functional domains, while the paternal frameshift mutation (c.1125_1132del) mislocalizes the protein to the nucleus. Both defects synergistically disrupt desmosomal integrity in cardiomyocytes. These findings expand the PKP2-associated genotype-phenotype spectrum and provide molecular basis for prenatal diagnosis and genetic counseling in high-risk families.

Microalgae surviving in extreme conditions evolve tolerance mechanisms to diverse environmental stresses. Environmental nitrogen limitation or nitrogen starvation poses a significant threat to the growth of microalgae, but it is an effective factor in inducing lipid accumulation in many microalgal species. In this study, we report the genome sequence of a promising oil-producing strain, Vischeria sp. WL1, which is capable of resisting long-term nitrogen starvation and responds rapidly to nitrogen recovery. Its genome comprises 127 Mb of nuclear DNA and 17,392 protein-coding genes. Comparative genomic and transcriptomic analyses identified a group of genes involved in nitrate metabolism and lipid accumulation. Heterologous expression of three candidate genes in the model cyanobacterium Synechocystis sp. PCC 6803 demonstrated their effects on restoring the cellular chlorophyll upon nitrogen recovery. Our results provide novel insights into the molecular basis of metabolic shifts in response to nitrogen starvation and recovery in microalgae.

In drylands, microalgae dwelling in the biocrust are inevitably confronted with nitrogen deficiency and desiccation stress, despite the protection afforded by the soil biological complex. However, the environmental adaptive features and mechanisms of these microalgae remain largely unknown. In this study, we explored the adaptive changes of a biocrust-derived unicellular microalga, Vischeria sp. WL1 (Eustigmatophyceae), in the face of long-term nitrogen deficiency. Attention was focused on the alterations in cell wall properties and the associated desiccation resistance. After exposure to long-term nitrogen deficiency, the cell walls of Vischeria sp. WL1 thickened substantially, accompanied by enhanced rigidity and an improvement in desiccation resistance. In contrast, Vischeria sp. WL1 cells cultivated under nitrogen-replete conditions were highly vulnerable to desiccation stress. Additional cell wall alterations after nitrogen starvation included distinct surface sculpturing, variations in monosaccharide composition, and changes in functional groups. Collectively, this study provides valuable insights into the survival strategies of biocrust-derived microalgae in nitrogen-deficient dryland environments.

Dynamic changes in diurnal light and temperature are a natural phenomenon, particularly pronounced in arid environments. However, it remains unclear whether the coupling of diurnal light and temperature fluctuations contributes to the capability and evolution of lipid accumulation in arid terrestrial microalgae. Here, we characterized the effects of diurnal light and temperature fluctuations on the growth, photosynthesis, lipids, carbohydrates, proteins and fatty acids in Vischeria sp. WL1, an oil-producing Eustigmatophyceae microalga sourced from an arid steppe. The photosynthetic activity parameters (F_v/F_m, PI_abs, ψ₀ and φ_E0) were the highest, while parameters of damage and energy dissipation (W_k and DI_O/RC) were the lowest, under the diurnal light cycle (DLC) among all conditions and then followed by the diurnal light–temperature cycle (DLTC). DLTC led to reduced growth and biomass but enhanced lipid accumulation, with lipid content reaching a maximum of 54.7% on day 4. This observation may suggest a carbon reallocation from carbohydrates toward lipid synthesis. DLTC resulted in an increase in the saturated fatty acids (SFA) content on day 12 and only in C18:2 among polyunsaturated fatty acids (PUFA) on day 4 while lowering eicosapentaenoic acid (EPA) concentration and content on day 12. Together, our findings will contribute to the understanding of the adaptive strategies of terrestrial microalgae to the arid environment, as well as the beneficial clues for exploring terrestrial microalgae for oil production.

Selenium (Se)-enriched microalgae are emerging as new food or agricultural resources. Thus far, the microalgae tested for Se accumulation or biofortification are still very limited. Here, we investigated the effects of selenite on the growth of three terrestrial microalgae (Vischeria sp. WL1, Chlorella sp. WL1, and Nostoc flagelliforme) and their total Se accumulation levels. The three microalgae were previously collected at the same location and show great application potential but differ in classification and growth speed. Three concentrations (10, 20, and 40 mg/L) of selenite were used for treatment. The former two species could resist 40 mg/L selenite but the last one could not. At the relatively optimal concentration (20 mg/L selenite), their specific growth rates were 0.09, 0.10, and 0.05 μ day⁻¹, respectively. Vischeria sp. WL1 could accumulate 3.3 mg/g dry weight (DW) Se after 16 days of cultivation; N. flagelliforme could accumulate 5.6 mg/g DW Se after 24 days of cultivation. Chlorella sp. WL1 accumulated a relatively lower amount of Se, being 0.74 mg/L DW after 18 days of cultivation, but its more rapid growth would be beneficial to saving production costs. These results indicate that three microalgae are capable of functioning as excellent carriers for Se nutrients. This study will contribute to enriching the microalgal resource pool for Se biofortification in food and agricultural areas.