Abstract
BACKGROUND: Oil in the form of triacylglycerols (TAGs) is quantitatively the most important storage form of energy for eukaryotic cells. Diacylglycerol acyltransferase (DGAT) is considered the rate-limiting enzyme for TAG accumulation. Chlorella, a unicellular eukaryotic green alga, has attracted much attention as a potential feedstock for renewable energy production. However, the function of DGAT1 in Chlorella has not been reported. RESULTS: A full-length cDNA encoding a putative diacylglycerol acyltransferase 1 (DGAT1, EC 2.3.1.20) was obtained from Chlorella ellipsoidea. The 2,142 bp open reading frame of this cDNA, designated CeDGAT1, encodes a protein of 713 amino acids showing no more than 40% identity with DGAT1s of higher plants. Transcript analysis showed that the expression level of CeDGAT1 markedly increased under nitrogen starvation, which led to significant triacylglycerol (TAG) accumulation. CeDGAT1 activity was confirmed in the yeast quadruple mutant strain H1246 by restoring its ability to produce TAG. Upon expression of CeDGAT1, the total fatty acid content in wild-type yeast (INVSc1) increased by 142%, significantly higher than that transformed with DGAT1s from higher plants, including even the oil crop soybean. The over-expression of CeDGAT1 under the NOS promoter in wild-type Arabidopsis thaliana and Brassica napus var. Westar significantly increased the oil content by 8-37% and 12-18% and the average 1,000-seed weight by 9-15% and 6-29%, respectively, but did not alter the fatty acid composition of the seed oil. The net increase in the 1,000-seed total lipid content was up to 25-50% in both transgenic Arabidopsis and B. napus. CONCLUSIONS: We identified a gene encoding DGAT1 in C. ellipsoidea and confirmed that it plays an important role in TAG accumulation. This is the first functional analysis of DGAT1 in Chlorella. This information is important for understanding lipid synthesis and accumulation in Chlorella and for genetic engineering to enhance oil production in microalgae and oil plants.
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Claims 7
Claim · model-written summary
CeDGAT1 expression under nitrogen starvation increased in Chlorella ellipsoidea.
Verbatim
t0“Chlorella ellipsoidea”
e1“expression level of CeDGAT1 markedly increased under nitrogen starvation”
Claim · model-written summary
CeDGAT1 over-expression raised oil content in Arabidopsis thaliana by 8-37%.
- Taxon
- Arabidopsis thaliana
Arabidopsis thalianae0 - Treatment
- over-expression of CeDGAT1 under the NOS promotere0
- Gene
- CeDGAT1e0
- Outcome
- oil contente0
- Direction
- increasede0
- Value
- 8-37%e0
- Comparator
- wild-type Arabidopsis thalianae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The over-expression of CeDGAT1 under the NOS promoter in wild-type Arabidopsis thaliana and Brassica napus var. Westar significantly increased the oil content by 8-37% and 12-18% and the average 1,000-seed weight by 9-15% and 6-29%, respectively”
Claim · model-written summary
CeDGAT1 over-expression raised oil content in Brassica napus var. Westar by 12-18%.
- Taxon
- Brassica napus var. Westar
_Brassica_napus_-_Habit.jpg?width=60)
Brassica napuse0 - Treatment
- over-expression of CeDGAT1 under the NOS promotere0
- Gene
- CeDGAT1e0
- Outcome
- oil contente0
- Direction
- increasede0
- Value
- 12-18%e0
- Comparator
- wild-typee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
_Brassica_napus_-_Habit.jpg?width=500)
Verbatim
e0“The over-expression of CeDGAT1 under the NOS promoter in wild-type Arabidopsis thaliana and Brassica napus var. Westar significantly increased the oil content by 8-37% and 12-18% and the average 1,000-seed weight by 9-15% and 6-29%, respectively”
Claim · model-written summary
CeDGAT1 over-expression raised average 1,000-seed weight in Arabidopsis by 9-15%.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Treatment
- over-expression of CeDGAT1 under the NOS promotere0
- Outcome
- average 1,000-seed weighte0
- Direction
- increasede0
- Value
- 9-15%e0
- Comparator
- wild-type Arabidopsis thalianae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The over-expression of CeDGAT1 under the NOS promoter in wild-type Arabidopsis thaliana and Brassica napus var. Westar significantly increased the oil content by 8-37% and 12-18% and the average 1,000-seed weight by 9-15% and 6-29%, respectively”
Claim · model-written summary
CeDGAT1 over-expression raised average 1,000-seed weight in Brassica napus by 6-29%.
- Taxon
- Brassica napus var. WestarBrassica napuse0
- Treatment
- over-expression of CeDGAT1 under the NOS promotere0
- Outcome
- average 1,000-seed weighte0
- Direction
- increasede0
- Value
- 6-29%e0
- Comparator
- wild-typee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The over-expression of CeDGAT1 under the NOS promoter in wild-type Arabidopsis thaliana and Brassica napus var. Westar significantly increased the oil content by 8-37% and 12-18% and the average 1,000-seed weight by 9-15% and 6-29%, respectively”
Claim · model-written summary
CeDGAT1 over-expression did not alter seed oil fatty acid composition in either plant.
- Taxon
- Arabidopsis thaliana and Brassica napus var. WestarArabidopsis thalianaBrassica napuse0
- Treatment
- over-expression of CeDGAT1e1
- Outcome
- fatty acid composition of the seed oile2
- Direction
- did not altere2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Arabidopsis thaliana and Brassica napus var. Westar”
e1“over-expression of CeDGAT1”
e2“did not alter the fatty acid composition of the seed oil”
Claim · model-written summary
The net increase in 1,000-seed total lipid content reached 25-50% in both transgenic plants.
- Taxon
- Arabidopsis and B. napusArabidopsisBrassica napuse1
- Outcome
- 1,000-seed total lipid contente1
- Direction
- increasee1
- Value
- 25-50%e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“transgenic Arabidopsis and B. napus”
e1“The net increase in the 1,000-seed total lipid content was up to 25-50% in both transgenic Arabidopsis and B. napus”