Table 2.
Effect of different genetic modifications for enhancing PUFAs’ accumulation in microalgae. Studies are grouped by genetic modification, such as overexpression, silencing/knock-out, and heterologous expression, and then by the pathway in which the gene of interest is involved. The table represents the results obtained through specific genetic modifications. Genes and pathways are reported in Uniprot (https://www.uniprot.org/uniprot, accessed on 29 November 2021). Differences are shown as percentage increases, indicating the surplus over the wild-type control condition.
| Overexpression | |||||
| Gene | Pathway | Microalgal Species | Results | Reference | |
| AGPAT1 | TAG biosynthesis | P. tricornutum | +50% EPA, +50% DHA content, +80% TAG content | [91] | |
| GPAT | TAG biosynthesis | P. tricornutum | +41% PUFA content | [92] | |
| DGAT2 | TAG biosynthesis | P. tricornutum | +76% EPA content, +35% neutral lipid content | [93] | |
| DGAT2 | TAG biosynthesis | P. tricornutum | +100% total lipid, +80% TAG content, +20% EPA content | [94] | |
| DGAT2 | TAG biosynthesis | N. oceanica | +69% neutral lipid content | [95] | |
| DGAT1A | TAG biosynthesis | N. oceanica | +39% TAG content | [96] | |
| DGTT1-3 | TAG biosynthesis | C. reinhardtii | no changes in lipid content | [97] | |
| DGTT4 | TAG biosynthesis | C. reinhardtii | +2800%TAG content | [98] | |
| GPAT, DGAT2 | TAG biosynthesis | P. tricornutum | +170% total lipid content | [99] | |
| GK | TAG biosynthesis | F. solaris | +12% total lipid content | [100] | |
| GPDH | TAG biosynthesis | P. tricornutum | +60% TAG content | [101] | |
| LPAAT1 | TAG biosynthesis | C. reinhardtii | +20% TAG content | [102] | |
| thioesterase | FA biosynthesis | P. tricornutum | +72% total lipid, +10% EPA content | [103] | |
| TE | FA biosynthesis | P. tricornutum | +16% EPA content | [103] | |
| ACP, KAS, FAT | FA biosynthesis | H. pluvialis | +100% EPA, +340%DHA content, +32% total FA content | [104] | |
| ME | FA biosynthesis | P. tricornutum | +150% total lipid content, −10% PUFA content | [105] | |
| MCAT | FA biosynthesis | N. oceanica | +31% neutral lipid, +8% EPA content | [106] | |
| MCAT | FA biosynthesis | Schizochytrium sp. | +172.5% EPA, +81.5% DHA, +69.2% DPA content | [107] | |
| FA elongase | FA biosynthesis | T. pseudonana | +40% EPA, +350% DHA content | [108] | |
| Δ5 desaturase | FA biosynthesis | P. tricornutum | +65% TAG content, +58% EPA content | [109] | |
| Δ12 desaturase | FA biosynthesis | N. oceanica | +75% AA content | [110] | |
| bHLH2 | transcription factor | N. salina | +33% total lipid content | [111] | |
| DOF | transcription factor | C. reinhardtii | +100% total lipid content | [112] | |
| DOF | transcription factor | C. reinhardtii | +170% total lipid content | [113] | |
| PSR1 | transcription factor | C. reinhardtii | no quantified reduction of neutral lipid content | [114] | |
| PSR1 | transcription factor | C. reinhardtii | +10% TAG content | [115] | |
| bZIP | transcription factor | N. salina | +50% total lipid content | [116] | |
| PNPLA3 | lipid turnover | P. tricornutum | +70% neutral lipid, +26% PUFA content | [117] | |
| LDP1 | lipid droplet metabolism | P. tricornutum | +30% total lipid, +40% neutral lipid content | [118] | |
| ACCase | pyruvate metabolism | C. cryptica | no changes in lipid content | [119] | |
| G6PD | carbohydrates metabolism | P. tricornutum | +170% total lipid content | [120] | |
| NOA | nitric oxide metabolism | P. tricornutum | +80% neutral lipid, +400% TAG content | [121] | |
| Silencing | |||||
|---|---|---|---|---|---|
| Gene | Pathway | Method | Microalgal Species | Results | Reference |
| AGPase | Carbohydrates’ metabolism | random mutagenesis | C. reinhardtii | +250% total lipids, +900% TAG content | [122] |
| isoamylase | Carbohydrates’ metabolism | random mutagenesis | C. reinhardtii | +450% total lipid content | [123] |
| UGPase | Carbohydrates’ metabolism | TALEN | P. tricornutum | +4400% TAG content | [124] |
| UGPase | Carbohydrates’ metabolism | RNAi | P. tricornutum | +4% total lipid content | [125] |
| CS | Carbohydrates’ metabolism | RNAi | T. pseudonana | +200% TAG content | [126] |
| SLM1 | Carbohydrates’ metabolism | random mutagenesis | S. obliquus | +51% TAG content | [127] |
| PEPC1 | pyruvate metabolism | CRISPRi | C. reinhardtii | +74% total lipid content | [128] |
| PEPC1 | pyruvate metabolism | RNAi | C. reinhardtii | +20% TAG content | [129] |
| PEPC1, PEPC2 | pyruvate metabolism | RNAi | C. reinhardtii | +48% FA content | [130] |
| PEPCK | pyruvate metabolism | RNAi | P. tricornutum | +40% total lipid content | [131] |
| CIS | pyruvate metabolism | RNAi | C. reinhardtii | +170% TAG content | [129] |
| PDK | pyruvate metabolism | RNAi | P. tricornutum | +82% neutral lipid, no changes in FA content | [132] |
| lipase | lipid turnover | RNAi | T. pseudonana | +300% EPA, +220% DHA content | [133] |
| omTGL | lipid turnover | RNAi | P. tricornutum | +70% EPA content | [134] |
| TGL1 | lipid turnover | RNAi | P. tricornutum | +200% TAG, +10% EPA content | [135] |
| LIP1 | lipid turnover | RNAi | C. reinhardtii | +150% TAG content | [136] |
| ACX2 | Β oxidation | insertional mutagenesis | C. reinhardtii | +400% neutral lipid, +70% TAG content | [137] |
| MLDP | lipid droplet metabolism | RNAi | C. reinhardtii | no changes in TAG content | [138] |
| LDP1 | lipid droplet metabolism | RNAi | P. tricornutum | −20% total lipid content | [130] |
| PDAT | TAG biosynthesis | RNAi | C. reinhardtii | general reduction of all TAG classes content | [139] |
| SAD | FA biosynthesis | RNAi | C. reinhardtii | +40% stearic acid content | [140] |
| ω-3-DES | FA biosynthesis | homologous recombination | C. vulgaris | no changes in PUFA and FA content | [141] |
| TES1 | FA biosynthesis | TALEN | P. tricornutum | +70% TAG content | [142] |
| PDH | FA biosynthesis | RNAi | C. reinhardtii | −50% FA content | [143] |
| DGTT | FA biosynthesis | RNAi | C. reinhardtii | −35% TAG content | [144] |
| NR | N assimilation | TALEN | P. tricornutum | +20% TAG content | [145] |
| NR | N assimilation | RNAi | P. tricornutum | +43% total lipid content | [146] |
| ZnCys | transcription factor | RNAi | N. gaditana | +35% total lipid content | [147] |
| - | - | random mutagenesis | P. lutheri | +33% EPA, +33% DHA content | [148] |
| - | - | insertional mutagenesis | N. oceanica | +180% PUFA, +40% EPA content | [149] |
| Heterologous expression | |||||
| Gene | Pathway | Source species | Receiver species | Results | Reference |
| Genes from microalgae in other microalgae | |||||
| GPAT | TAG biosynthesis | L. incisa | C. reinhardtii | +50% FA content | [150] |
| ELO5 | FA biosynthesis | O. tauri | P. tricornutum | +700% DHA content | [151] |
| ELO5, DES6 | FA biosynthesis | O. tauri | P. tricornutum | +800% DHA content | [151] |
| Δ5DES | FA biosynthesis | T. aureum | A. limacinum | +360% EPA, +1220% AA content | [152] |
| ME | FA biosynthesis | P. tricornutum | C. pyrenoidosa | +220% neutral lipid content | [105] |
| (Bn)AccD, (Cr)ME | pyruvate metabolism | B. napus, C. reinhardtii | D. salina | +12% total lipid content | [153] |
| ACCase | pyruvate metabolism | C. cryptica | N. saprophila | no changes in lipid content | [119] |
| thioesterase | FA biosynthesis | D. tertiolecta | C. reinhardtii | +50% FA content | [154] |
| DGAT2 | TAG biosynthesis | C. reinhardtii | S. obliquus | +85% total lipid content | [155] |
| Genes from other organisms in microalgae | |||||
| DGAT2 | TAG biosynthesis | B. napus (plant) | P. tricornutum | +12% ALA content | [156] |
| DGA1 | TAG biosynthesis | S. cerevisiae (yeast) | P. tricornutum | +130% TAG content | [157] |
| OLEO3 | TAG biosynthesis | A. thaliana (plant) | P. tricornutum | +40% TAGcontent | [157] |
| (Sc)DGA1, (At)OLEO3 | TAG biosynthesis | S. cerevisiae (yeast), A. thaliana (plant) | P. tricornutum | +260% TAG content | [157] |
| (Sc)G3PDH-GPAT-LPAAT, (Yl)DGATs | TAG biosynthesis | S. cerevisiae, Y. lipolytica (yeasts) | C. minutissima | +120% total lipid content | [158] |
| Δ3DES | FA biosynthesis | S. dicilina (yeast) | Schizochytrium sp. | +3% DHA content | [159] |
| ACP reductase | FA biosynthesis | Synechocystis sp. (cyanobacteria) | C. merolae | +133% TAG content | [160] |
| (Cc)C14-TE, (Uc)C12-TE | FA biosynthesis | C. camphora, U. californica (plants) | P. tricornutum | +80% TAG content | [161] |
| (Cc)C14-TE, (Uc)C12-TE, (Ch)KAS | FA biosynthesis | C. camphora, U. californica, C. hookeriana (plants) | D. tertiolecta | +4% FA content | [162] |
| C14-TE, C10-TE, ACP | FA biosynthesis | C. lanceolata (plant) | C. reinhardtii | general increase in different FAs classes content | [163] |
| (Bn)AccD, (Cr)ME | pyruvate metabolism | B. napus (plant), C. reinhardtii | D. salina | +12% total lipid content | [153] |
| ACC1 | pyruvate metabolism | S. cerevisiae (yeast) | S. quadricauda | +60% FA content | [164] |
| ACC1, GDP1, GUT1 | pyruvate metabolism | S. cerevisiae (yeast) | S. quadricauda | +50% total lipid content | [164] |
| ACS | pyruvate metabolism | E. coli (bacteria) | Schizochytrium sp. | no changes in lipid content | [165] |
| (An)PhyA, (Ot)Elo5 | phytate metabolism | A. niger (yeast), O. tauri | P. tricornutum | +10% DHA, −25% EPA content | [166] |
| (Ec)AppA, (Ot)Elo5 | phytate metabolism | E. coli (bacteria), O. tauri | P. tricornutum | +12% DHA, −18% EPA content | [166] |
| DOF4 | transcription factor | G. max (plant) | C. ellipsoidea | +53% total lipid content | [167] |
| WRI1 | transcription factor | A. thaliana (plant) | N. salina | +64% tota lipid content | [168] |
| Genes from microalgae in other organisms | |||||
| antisense PEPC | pyruvate metabolism | Anabaena sp. | E. coli (bacteria) | +47% lipid content | [169] |
| ACCase | pyruvate metabolism | P. tricornutum | E. coli (bacteria) | +100% neutral lipid content | [170] |
| Δ9-ELO | FA biosynthesis | I. galbana | A. thaliana (plant) | +18% PUFA content | [171] |
| Δ9-ELO (codon optimized) | FA biosynthesis | I. galbana | A. thaliana (plant) | +64% PUFA content | [172] |
| Δ6-DES | FA biosynthesis | M. pusilla | A. thaliana (plant) | +26% EPA content | [173] |
| (Ig)Δ9E, (Eg)Δ8D, (Ma)Δ5D | FA biosynthesis | I. galbana, E. gracilis, M. alpina | A. thaliana (plant) | +23% PUFA, +3% EPA, +7% AA content | [171] |
| (Pt)Δ5D, (Pt)Δ6D, (Pp)Δ6E | FA biosynthesis | P. tricornutum, Physcomitrella patens | N. tabacum (plant) | +30% PUFA content | [174] |
| (Pt)Δ5D, (Pt)Δ6D, (Pp)Δ6E | FA biosynthesis | P. tricornutum, P. patens | L. usitatissimum (plant) | +30% PUFA content | [174] |
| (Sc)PUFA-synthase, (No)PPTase | FA biosynthesis | Schizochytrium sp., Nostoc sp. |
A. thaliana (plant) B. napus (plant) |
+4% DHA, +1% EPA content | [175] |
| ELO5 | FA biosynthesis | P. tricornutum | P. pastoris (yeast) | no quantified increase in DPA and DTA content | [176] |
| (Pt)ELO5, (Is)DES4 | FA biosynthesis | P. tricornutum, I. sphaerica | P. pastoris (yeast) | +3% DPA, +2.35% DHA content | [176] |
| DES2 | FA biosynthesis | C. vulgaris | S. cerevisiae (yeast) | no quantified reduction of LA content | [177] |
| DGTT2 | FA biosynthesis | C. reinhardtii | S. cerevisiae (yeast) | +800% TAG content | [178] |
| (Pt)Δ5D, (Pt)Δ6D, (Pp)Δ6E | FA biosynthesis | P. tricornutum, P. patens | S. cerevisiae (yeast) | +0.23% EPA, +0.17% AA content | [179] |
| DES6 | FA biosynthesis | M. pusilla | M. alpina (yeast) | +2500% EPA content | [180] |
| Δ6ELO | FA biosynthesis | Isochrysis sp. | E. coli (bacteria) | +6% SDA, +3% GLA content | [181] |
| (Iso)Δ6ELO, (Pav)Δ5DES | FA biosynthesis | Isochrysis sp., Pavlova sp. | E. coli (bacteria) | no quantified increase of AA and EPA content | [182] |