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Effects of overexpression of a bHLH transcription factor on biomass and lipid production in Nannochloropsis salina.

Kang NK, Jeon S, Kwon S, Koh HG, Shin SE, Lee B, Choi GG, Yang JW, Jeong BR, Chang YK - Biotechnol Biofuels (2015)

Bottom Line: These enhanced growth and nutrient uptake resulted in increased productivities of biomass and FAME.Conclusively, the improved growth in the transformants can be associated with the enhanced nutrient uptake.We are currently assessing their potential for scale-up cultivation with positive outcomes.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemical and Biomolecular Engineering, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon, 305-701 Republic of Korea.

ABSTRACT

Background: Microalgae are considered promising alternative energy sources because they consume CO2 and accumulate large amounts of lipids that can be used as biofuel. Nannochloropsis is a particularly promising microalga due to its high growth rate and lipid content, and the availability of genomic information. Transcription factors (TFs) are global regulators of biological pathways by up- or down-regulation of related genes. Among these, basic helix-loop-helix (bHLH) TFs regulate growth, development, and stress responses in plants and animals, and have been identified in microalgae. We identified two bHLH TFs in the genome of N. salina CCMP1776, NsbHLH1, and NsbHLH2, and characterized functions of NsbHLH2 that may be involved in growth and nutrient uptake.

Results: We obtained NsbHLH2 overexpressing transformants of N. salina CCMP1776 by particle bombardment and confirmed that these were stable transformants. Quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting using antibodies against the FLAG tag that was attached at the end of the coding sequence confirmed the expression of the NsbHLH2 protein under various culture conditions. The qRT-PCR results also indicated that the endogenous and transgenic expression of NsbHLH2 was reduced under stressed conditions. Overexpression of NsbHLH2 led to increased growth rate in the early growth period, and concomitantly higher nutrient uptake, than wild type (WT). These enhanced growth and nutrient uptake resulted in increased productivities of biomass and FAME. For example, one of the transformants, NsbHLH2 3-6, showed increased biomass productivity by 36 % under the normal condition, and FAME productivity by 33 % under nitrogen limitation condition. Conclusively, the improved growth in the transformants can be associated with the enhanced nutrient uptake. We are currently assessing their potential for scale-up cultivation with positive outcomes.

Conclusion: Overexpression of NsbHLH2 led to enhanced growth rate and nutrient uptake during the early growth phase, and increased biomass and FAME productivity, especially in the later period under normal and stressed conditions. Based on these results, we postulate that NsbHLH2 can be employed for the industrial production of biodiesel from N. salina.

No MeSH data available.


Related in: MedlinePlus

Nutrient consumption during growth of NsbHLH2 transformants. a Nutrient uptake was estimated by measuring concentrations of nitrate (a, c, e) and phosphate (b, d, f) in the culture media under normal (a, b), N limitation (c, d), and osmotic stress conditions (e, f). Cells were cultivated at 25 °C, 120 rpm, 120 µmol photons/m2/s of fluorescent light, and 0.5 vvm of 2 % CO2. Data points represent means and standard errors (n = 4)
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Fig5: Nutrient consumption during growth of NsbHLH2 transformants. a Nutrient uptake was estimated by measuring concentrations of nitrate (a, c, e) and phosphate (b, d, f) in the culture media under normal (a, b), N limitation (c, d), and osmotic stress conditions (e, f). Cells were cultivated at 25 °C, 120 rpm, 120 µmol photons/m2/s of fluorescent light, and 0.5 vvm of 2 % CO2. Data points represent means and standard errors (n = 4)

Mentions: In order to investigate the mechanism behind increased accumulation of biomass and FAME productivity, we analyzed nutrient uptake in the NsbHLH2 transformants (Fig. 5). The NsbHLH2 transformants consumed nitrate and phosphate more rapidly under all culture conditions, in parallel with their rapid growth during the early growth phase (Fig. 3). However, as most of the nutrients were consumed by day 8, the specific growth rates, FAME productivity, and DCWs of the transformants became similar with those of WT (Fig. 4; Table 2).Fig. 5


Effects of overexpression of a bHLH transcription factor on biomass and lipid production in Nannochloropsis salina.

Kang NK, Jeon S, Kwon S, Koh HG, Shin SE, Lee B, Choi GG, Yang JW, Jeong BR, Chang YK - Biotechnol Biofuels (2015)

Nutrient consumption during growth of NsbHLH2 transformants. a Nutrient uptake was estimated by measuring concentrations of nitrate (a, c, e) and phosphate (b, d, f) in the culture media under normal (a, b), N limitation (c, d), and osmotic stress conditions (e, f). Cells were cultivated at 25 °C, 120 rpm, 120 µmol photons/m2/s of fluorescent light, and 0.5 vvm of 2 % CO2. Data points represent means and standard errors (n = 4)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4666162&req=5

Fig5: Nutrient consumption during growth of NsbHLH2 transformants. a Nutrient uptake was estimated by measuring concentrations of nitrate (a, c, e) and phosphate (b, d, f) in the culture media under normal (a, b), N limitation (c, d), and osmotic stress conditions (e, f). Cells were cultivated at 25 °C, 120 rpm, 120 µmol photons/m2/s of fluorescent light, and 0.5 vvm of 2 % CO2. Data points represent means and standard errors (n = 4)
Mentions: In order to investigate the mechanism behind increased accumulation of biomass and FAME productivity, we analyzed nutrient uptake in the NsbHLH2 transformants (Fig. 5). The NsbHLH2 transformants consumed nitrate and phosphate more rapidly under all culture conditions, in parallel with their rapid growth during the early growth phase (Fig. 3). However, as most of the nutrients were consumed by day 8, the specific growth rates, FAME productivity, and DCWs of the transformants became similar with those of WT (Fig. 4; Table 2).Fig. 5

Bottom Line: These enhanced growth and nutrient uptake resulted in increased productivities of biomass and FAME.Conclusively, the improved growth in the transformants can be associated with the enhanced nutrient uptake.We are currently assessing their potential for scale-up cultivation with positive outcomes.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemical and Biomolecular Engineering, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon, 305-701 Republic of Korea.

ABSTRACT

Background: Microalgae are considered promising alternative energy sources because they consume CO2 and accumulate large amounts of lipids that can be used as biofuel. Nannochloropsis is a particularly promising microalga due to its high growth rate and lipid content, and the availability of genomic information. Transcription factors (TFs) are global regulators of biological pathways by up- or down-regulation of related genes. Among these, basic helix-loop-helix (bHLH) TFs regulate growth, development, and stress responses in plants and animals, and have been identified in microalgae. We identified two bHLH TFs in the genome of N. salina CCMP1776, NsbHLH1, and NsbHLH2, and characterized functions of NsbHLH2 that may be involved in growth and nutrient uptake.

Results: We obtained NsbHLH2 overexpressing transformants of N. salina CCMP1776 by particle bombardment and confirmed that these were stable transformants. Quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting using antibodies against the FLAG tag that was attached at the end of the coding sequence confirmed the expression of the NsbHLH2 protein under various culture conditions. The qRT-PCR results also indicated that the endogenous and transgenic expression of NsbHLH2 was reduced under stressed conditions. Overexpression of NsbHLH2 led to increased growth rate in the early growth period, and concomitantly higher nutrient uptake, than wild type (WT). These enhanced growth and nutrient uptake resulted in increased productivities of biomass and FAME. For example, one of the transformants, NsbHLH2 3-6, showed increased biomass productivity by 36 % under the normal condition, and FAME productivity by 33 % under nitrogen limitation condition. Conclusively, the improved growth in the transformants can be associated with the enhanced nutrient uptake. We are currently assessing their potential for scale-up cultivation with positive outcomes.

Conclusion: Overexpression of NsbHLH2 led to enhanced growth rate and nutrient uptake during the early growth phase, and increased biomass and FAME productivity, especially in the later period under normal and stressed conditions. Based on these results, we postulate that NsbHLH2 can be employed for the industrial production of biodiesel from N. salina.

No MeSH data available.


Related in: MedlinePlus