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Table 1 Influence of genes supplying substrates for lipid synthesis in transgenic strains

From: The dilemma for lipid productivity in green microalgae: importance of substrate provision in improving oil yield without sacrificing growth

Genes Description Host species Method of intervention Effects (relative to control) Inferred role Ref.
PDK Pyruvate dehydrogenase kinase Phaeodactylum tricornutum Antisense knockdown 33–82% more neutral lipids in 2 mutants PDK deactivates Pyruvate dehydrogenase complex (PDC). Knocking down PDK increases acetyl-CoA production from pyruvate via PDC [101]
NADK3 Arabidopsis thaliana NAD(H) kinase (AtNADK3) Chlorella pyrenoidosa Gene overexpression Total lipid content increased by 45.3–110.4%; NADPH content increased by 39.3–79.9% Heterologous NADH kinase increases NADPH which drives reductive biosynthesis reactions such as FA synthesis [72]
ACS E. coli Acetyl-CoA synthetase (ACS) Schizochytrium sp. Gene overexpression Total lipid content increased by 6.4–11.4%; Biomass increased by 24.3–29.9% Heterologous ACS overexpression improved utilization of acetate as a carbon resource for growth and lipid synthesis [78]
ACL Mus musculus ATP:citrate lyase Yarrowia lipolytica Gene overexpression Total lipid content increased by 50.6–215.1%; Citrate content decreased by 32% Heterologous expression of ACL with a low Km value for citrate increases lipid synthesis by providing more cytosolic acetyl-CoA as substrates [138]
PDH E1α E1 alpha subunit of the Pyruvate Dehydrogenase Complex Chlamydomonas reinhardtii Artificial microRNA knockdown Total lipid content decreased by 25–40%; Lower chlorophyll content, lower photosynthetic yield on PSII, and lower biomass in mutants PDC serves an essential role in the supply of carbon precursors for FA synthesis under photoautotrophy [100]
ME Malic enzyme Phaeodactylum tricornutum Gene overexpression 2.3- to 2.5-fold more neutral lipids in 2 mutants; growth rate unaffected ME could increase lipid synthesis without affecting biomass accumulation by providing NADPH [128]
ME Phaeodactylum tricornutum malic enzyme (PtME) Chlorella pyrenoidosa Gene overexpression 2.4- to 3.2-fold more neutral lipids in 2 mutants; growth rate unaffected Heterologous ME could increase lipid synthesis without affecting biomass accumulation by providing NADPH [129]
G6PDH Glucose-6-phosphate dehydrogenase Mortierella alpina RNAi knockdown Total lipid content decreased by 50%; NADPH content decreased by 40% G6PDH is a critical component of the Oxidative Pentose Phosphate Pathway which enables efficient lipid synthesis [66]
ACL/ME ATP:citrate lyase and Malic enzyme Yarrowia lipolytica Five gene modifications including overexpression of ME and ACL subunit 1 and subunit 2 Total lipid content increased to 74%, a 15-fold improvement over wild type (16.8%) ACL and ME cooperatively divert carbon precursors and reducing power towards lipid synthesis, and in conjunction with other modifications, lead to enhanced lipid accumulation [85]