Development of a Nuclear Transformation System for Oleaginous Green Alga Lobosphaera (Parietochloris) incisa and Genetic Complementation of a Mutant Strain, Deficient in Arachidonic Acid Biosynthesis

Abstract Global primary production is driven largely by oxygenic photosynthesis, with algae as major contributors. The green alga Chromochloris zofingiensis reversibly switches off photosynthesis in the presence of glucose in the light and augments production of biofuel precursors (triacylglycerols) and the high-value antioxidant astaxanthin. Here we used forward genetics to reveal that this photosynthetic and metabolic switch is mediated by the glycolytic enzyme hexokinase (CzHXK1). In contrast to wild-type, glucose-treated hxk1 mutants do not shut off photosynthesis or accumulate astaxanthin, triacylglycerols, or cytoplasmic lipid droplets. We show that CzHXK1 is critical for the regulation of genes related to photosynthesis, ketocarotenoid synthesis and fatty acid biosynthesis. Sugars play fundamental regulatory roles in gene expression, physiology, metabolism, and growth in plants and animals, and we introduce a relatively simple, emerging model system to investigate conserved eukaryotic sugar sensing and signaling at the base of the green lineage.

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Improvement of Chloroplast Transformation Using CRISPR/Cas9

Journal of Biobased Materials and Bioenergy ◽

10.1166/jbmb.2020.1970 ◽

2020 ◽

Vol 14 (3) ◽

pp. 401-407

Author(s):

Ning Tang ◽

Yumei Xia ◽

Yijie Zhan ◽

Junhao Dan ◽

Mulan Yu ◽

...

Keyword(s):

Dna Damage ◽

Homologous Recombination ◽

Gene Editing ◽

Transformation Efficiency ◽

Chloroplast Transformation ◽

Nuclear Transformation ◽

Important Research ◽

Transformation System ◽

Repair Mechanism ◽

Damage Repair

Chloroplasts are organelles that contain genetic materials (DNA) in higher plant cells. The special genetic characteristics of chloroplasts mean that plasmid transformation has important research value, so it has become an important research direction second to nuclear transformation. Although the techniques of chloroplast genome modification have been successfully applied in tobacco and extended to other high plants, there are still many limitations. Exogenous genes are integrated into the chloroplast genome through homologous recombination. Therefore, the low efficiency of homologous recombination directly limits transformation efficiency. Gene editing with fixed-point cutting function and DNA damage repair mechanism may effectively improve the efficiency. In the present study, we aimed to use CRISPR/Cas9 to cut the site between two homologous recombinant fragments in chloroplast transformation to improve the efficiency by activating the DNA damage repair mechanism. The Cas9 gene and gRNA were added to the chloroplast transformation system of tobacco by co-transformation or integration into a transformation vector. The acquired resistant plants were screened by multiple selection of spectinomycin and chloroplast DNA was isolated for molecular detection by PCR. The results showed that the efficiency of chloroplast transformation increased by 6–10 times with the addition of gene editing technology. Although the transformation efficiency was still far below the level of nuclear transformation, this study may help to increase the efficiency of the plant chloroplast transformation system, and expand the types of plant receptors.

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