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Microalgae are interesting chassis cells in synthetic biology because they play a significant role in primary productivity and global photosynthesis.
Researchers from the Chinese Academy of Sciences’ Qingdao Institute of Bioenergy and Bioprocess Technology (QIBEBT) have uncovered the distribution pattern and dynamic changes in DNA N6-methyladenine (6mA) at a single-base resolution in both wild-type and 6mA-disrupted mutant strains. This has led to the revelation of 6mA’s critical role in lipid accumulation, particularly in high light conditions. Their study was published in Plant Communications.
Renowned for its resilience and efficacy in outdoor cultivation, Nannochloropsis oceanica confers benefits like swift development, a powerful lipid synthesis capacity, great carbon dioxide tolerance, and superior unsaturated fatty acid content. Its tiny genome (around 30 Mb) and haploid makeup make it amenable to highly efficient editing of a variety of genetic modifications, such as gene knockout, overexpression, large genomic fragment deletion, and homologous recombination.
Uncovering the Function of 6mA in Gene Expression
One significant DNA methylation alteration is 6mA. The whole-genome 6mA landscape of Nannochloropsis oceanica was unveiled by the researchers through the use of single-molecule real-time sequencing. The findings show that 6mA is preferentially enriched in the AGGYV motif, that its levels are higher in transposons and 3′ untranslated regions, and that it is closely related to active transcription.
The study’s co-first author, GONG Yanhai, stated, “We observed a gradual increase of 6mA along the gene transcription direction, with specific enrichment near splice donors and transcription termination sites.”
Furthermore, compared to lowly expressed genes, highly expressed genes have a higher abundance of 6mA in the genome, indicating a positive interaction between 6mA and general transcription factors.
Microalgae: A Green Revolution for Climate Action and Sustainability
Impact of Adjusting 6mA Levels
The 6mA methyltransferase gene (NO08G00280) was deleted by the researchers in order to further examine the consequences of 6mA. As a result, there was a decline in biomass and oil production as well as modifications to methylation patterns and the expression of important genes linked to the molybdenum cofactor, sulphate transporters, glycosyl transferase, lipase, and methionine sulphoxide reductase.
On the other hand, elevated 6mA levels and slower growth were seen with ablation of the demethylase gene (NO06G02500).
Prof. WANG Qintao, co-first author of the paper, stated, “These findings not only validated key enzymes in the epigenetic regulation pathway but also shed light on the pivotal role of 6mA in lipid accumulation in Nannochloropsis under high light conditions.”
Possibility of Industrial Uses
These results shed light on how industrial microalgae might use epigenetic genome alterations to boost biomass and lipid production efficiency. As part of the Nannochloropsis Design & Synthesis Initiative (NanDeSyn), which coordinates efforts to promote molecular breeding and synthetic biology research in commercial carbon-fixing, oil-producing microalgae, 26 research teams from eight countries are involved in this project.
We’ve worked together to create complete datasets that are publicly available, including transcriptomes, related mutations under different growth conditions, and whole-genome 6mA epigenetic modification maps. The scientific community can now access these invaluable resources by visiting the NanDeSyn website. Prof. XU Jian, the study’s corresponding author, stated, “Our shared objective is to advance industrial microalgae research by promoting the exchange of germplasm resources, genetic tools, and functional genomics information.”
Reference: “Genome-wide adenine N6-methylation map reveals epigenomic regulation of lipid accumulation in Nannochloropsis” by Yanhai Gong, Qintao Wang, Li Wei, Wensi Liang, Lianhong Wang, Nana Lv, Xuefeng Du, Jiashun Zhang, Chen Shen, Yi Xin, Luyang Sun and Jian Xu, 24 November 2023, Plant Communications.
