Arctic Sea Ice Microalga Chlamydomonas latifrons KNF0041: Identification and Statistical Optimization of Medium for Enhanced Biomass and Omega-3/Omega-6.

Polar microorganisms produce biologically active compounds that enable them to survive in harsh environments. These compounds have potential biomedical applications. The green microalga Chlamydomonas latifrons KNF0041, isolated from Arctic sea ice, has been found to produce polyunsaturated fatty acids (PUFAs), including omega-3 and omega-6, which have antioxidant properties. To improve the biomass production of strain KNF0041, statistical methods such as the Plackett-Burman design, Box-Behnken design, and response surface methodology (RSM) were utilized for medium optimization. The optimized medium was designed with increased potassium phosphate content and reduced acetic acid (AcOH) content. The use of the optimized medium resulted in an increase in the cell number as biomass of strain KNF0041 by 34.18% and the omega-3 and omega-6 fatty acid (FA) content by 10.04% and 58.29%, respectively, compared to that in normal TAP medium, which is known as the growth medium for Chlamydomonas culture. In this study, Chlamydomonas latifrons was discovered for the first time in the polar region and identified using morphology and molecular phylogenetic analyses, the secondary structures of the internal transcribed spacers, and optimized culture conditions. The results of this study provide an efficient method for the application of polar microalgae for the production of bioactive compounds.

The glacier melting process is an invisible barrier to the development of Antarctic subtidal macroalgal assemblages.

Ecological macroalgal succession in glacier-free areas has remained at the pioneer seral stage despite six decades of glacial retreat at Marian Cove, King George Island, Antarctica. With the rapid melting of glaciers in the West Antarctic Peninsula owing to global warming, a massive amount of meltwater is flowing into the coast, creating marine environmental gradients such as turbidity, water temperature, and salinity. This study examined the spatial and vertical distributions (up to a depth of 25 m) of macroalgal assemblages from nine sites in Maxwell Bay and Marian Cove. The macroalgal assemblages were analyzed for six sites located 0.2, 0.8, 1.2, 2.2, 3.6, and 4.1 km away from the glacier, including three sites where the glacial retreat history of Marian Cove could be estimated. To investigate the effects of meltwater, differences in the coastal environment were analyzed based on data collected from five stations located 0.4, 0.9, 3.0, 4.0, and 5.0 km away from the glacier. The macroalgal assemblages and marine environment were divided into two groups-inside and outside the cove-based on the region 2-3 km away from the glacier, which has been ice-free since 1956 and shows significant differences. In the three sites near the glacier front, Palmaria decipiens was dominant, and three to four species were distributed, whereas in the two sites outside the cove, nine and 14 species appeared, respectively, similar to the assemblage of the other three sites in Maxwell Bay. Palmaria decipiens, a representative opportunistic pioneer species in Antarctica, is dominant because of its physiological adaptation despite the high turbidity and low water temperature of the glacier front. This study shows that macroalgal assemblages in Antarctic fjord-like coves respond to glacial retreat and are valuable in understanding the macroalgal succession in Antarctica.

TLR3 forms a highly organized cluster when bound to a poly(I:C) RNA ligand.

Toll-like Receptor 3 (TLR3) initiates a potent anti-viral immune response by binding to double-stranded RNA ligands. Previous crystallographic studies showed that TLR3 forms a homodimer when bound to a 46-base pair RNA ligand. However, this short RNA fails to initiate a robust immune response. To obtain structural insights into the length dependency of TLR3 ligands, we determine the cryo-electron microscopy structure of full-length TLR3 in a complex with a synthetic RNA ligand with an average length of ~400 base pairs. In the structure, the dimeric TLR3 units are clustered along the double-stranded RNA helix in a highly organized and cooperative fashion with a uniform inter-dimer spacing of 103 angstroms. The intracellular and transmembrane domains are dispensable for the clustering because their deletion does not interfere with the cluster formation. Our structural observation suggests that ligand-induced clustering of TLR3 dimers triggers the ordered assembly of intracellular signaling adaptors and initiates a robust innate immune response.

Combined Cyclin-Dependent Kinase Inhibition Overcomes MAPK/Extracellular Signal-Regulated Kinase Kinase Inhibitor Resistance in Plexiform Neurofibroma of Neurofibromatosis Type I.

MAPK/extracellular signal-regulated kinase kinase (MEK) 1/2 inhibitors (MEKis) have recently achieved surprising success in treating unresectable plexiform neurofibromas (PNFs). However, few studies have investigated the mechanisms of MEKi resistance in patients with PNF. We determined the efficacy of six different MEKis for treating PNFs, explored drug resistance mechanisms, and identified potential combination therapies to overcome resistance. By screening drug efficacy among six MEKis in human NF1-deficient PNF cell lines, TAK-733 was found to reduce PNF cell viability the most. We then cultured the TAK-733‒resistant cells and explored the potential targets for further treatment. Both high-throughput drug screening and RNA sequencing analyses of MEKi-resistant PNF cells identified cyclin-dependent kinase inhibitors as potential agents for PNFs. Dinaciclib, a cyclin-dependent kinase inhibitor, showed synergistic effects on MEKi-resistant cells. Coadministration of dinaciclib and TAK-733 significantly reduced cell viability and inhibited sphere formation and colony formation. Dinaciclib did not affect MEK signaling but decreased the expression of several prosurvival proteins, including survivin and cyclin-dependent kinase 1, to induce apoptosis and inhibit mitosis. TAK-733/dinaciclib combination therapy induced tumor reduction in PNF patient‒derived xenografts mouse models. Therefore, the combination of MEKi and cyclin-dependent kinase inhibitor may be promising for treating inoperable PNFs, especially when drug resistance exists. Our findings provide evidence for future clinical trials with MEKi-resistant patients with PNF.

[Effects of tillage with mulching on potato yield and the characteristics of soil water and temperature in arid area of southern Ningxia]. / 宁南旱区耕作覆盖对马铃薯产量及土壤水热特征的影响.

To clarify the effects of tillage with mulching on potato yield and soil water and heat characteristics, we conducted a field experiment for two consecutive years in arid region of southern Ningxia. The results showed that tillage depths and mulching materials had significant impacts on soil water storage at 0-100 cm layer during the potato sowing period. The interactive effects of tillage depths and mulching materials were not significant. In 2019, the highest soil water storage was obtained in the subsoiling 30 cm with plastic film mulching, while soil water storage under the subsoiling 40 cm with straw mulch was the highest in 2020. Subsoiling 30 cm with plastic film mul-ching and subsoiling 40 cm with straw mulch significantly increased soil water storage by 16.9% and 33.4% compared with the plowing 15 cm with no mulch (CK), respectively. Tillage depths and mulching materials significantly affected soil water storage in the key growth period of potato. Among the tillage systems, the straw mulching plots and plastic film mulching plots had the strongest effect of soil water conservation. Irrespective of the mulching materials, soil water storage was significantly improved in the subsoiling 30-40 cm plots. Mulching materials and the interaction between tillage depths and mulching materials significantly affected soil effective accumulated temperature at 0-25 cm soil layer after sowing to budding. Among the tillage systems, the plastic film mulching plots significantly increased the average soil effective accumulated temperature by 9.3%, whereas the straw mulching plots significantly reduced the temperature by 18.7%, in comparison with no mulching plots. The highest soil effective accumulated temperature during the whole growth period was obtained in the subsoiling 30 cm with plastic film mulching and subsoiling 40 cm with plastic film mulching treatments in 2019 and 2020. The highest potato tuber yield and economic benefit in 2019 were found in the subsoiling 30 cm with straw mulching treatment, respectively, being 84.6% and 107.9% higher than CK. In 2020, the improvement effect of subsoiling 40 cm with straw mulch on potato tuber yield and economic benefit was the strongest, respectively, which were significantly increased by 81.7% and 105.7%, compared with CK. Tillage depths and mulching materials had significant interactive effects on the water and heat use efficiency of crop. The higher water use efficiency was obtained in the subsoiling 30-40 cm with straw mulch treatments, whereas the accumulated temperature use efficiency was increased significantly under different tillage depths with straw mulching treatments compared with CK. Soil water and effective accumulated temperature during the tuber formation stage were the main factors affecting potato total yield, with stronger effect of soil water than that of soil effective accumulated temperature. Therefore, the treatments of subsoiling 30-40 cm with straw mulch could improve soil moisture and heat condition, and realize potato yield and income increase and efficient use of water and heat resources, which have application and popularization value in dryland potato cultivation of southern Ningxia.

Mitochondrial genome of the Antarctic microalga Micractinium simplicissimum KSF0127 (Chlorellaceae, Trebouxiophyceae).

We report the first mitochondrial genome of the Antarctic microalga Micractinium simplicissimum KSF0127. The circular mitochondrial genome was 67,923 bp in length and contained 45 protein-coding genes, one ribosomal RNA gene, and 60 transfer RNA genes. The phylogenetic tree was constructed with eight previously reported mitogenome sequences and showed the phylogenetic position of M. simplicissimum KSF0127 within the Chlorellaceae family.

A cross-sectional survey on nutritional risk and prevalence of malnutrition per Global Leadership Initiative on Malnutrition criteria in patients with end-stage malignant gastrointestinal tumors in a tertiary (A) hospital in Changsha / 中华临床营养杂志

Objective:To investigate the nutritional risk and prevalence of malnutrition in patients with terminal stage gastrointestinal malignant tumors in a tertiary hospital in Changsha.Methods:Cluster sampling was used to conduct a cross-sectional survey of inpatients from Departments of Gastroenterology, Gastrointestinal Surgery, Hepatobiliary Surgery and Oncology in Hunan Provincial People's Hospital from January 2019 to July 2020. Nutritional Risk Screening 2002 (NRS 2002) was used to assess the prevalence of nutritional risk with malnutrition defined as concurrent presence of BMI < 18.5 kg/m 2, poor general condition and NRS 2002 nutritional impairment score of 3. Step 2 of Global Leadership Initiative on Malnutrition (GLIM) diagnostic criteria (without whole body muscle mass) was adopted to diagnose malnutrition. Step 3 of GLIM criteria was used to evaluate the prevalence of severe malnutrition. Results:A total of 802 patients registered in the 4 departments were selected for screening via cluster sampling and 514 were enrolled according to the inclusion/exclusion criteria. The prevalence of nutritional risk in patients with terminal stage gastrointestinal cancer was 49.8% (256/514). The prevalence of malnutrition and severe malnutrition per GLIM criteria were 41.6% (214/514) and 18.3% (94/514), respectively.Conclusions:Although nutritional support therapy is not recommended for patients with end-stage cancer. This paper suggests that the prevalence of nutritional risk and malnutrition in patients with end-stage gastrointestinal cancer is not as high as described in some articles.

30 years revisit survey for long-term changes in the Antarctic subtidal algal assemblage.

A long-term change of a subtidal macroalgal assemblage has been investigated in Maxwell Bay, King George Island (KGI) of the Antarctic coast by a revisit survey after 30 years. Field surveys were done by SCUBA diving at six sites in 2016-2018 to directly compare with the previous survey conducted in 1988-1993 at the same sites. The total number of macroalgal species was similar between the previous and the present survey, 25 and 27 species respectively. However, the macroalgal assemblage changed substantially with the average similarity of 48.2% between the two surveys. Also, the species-level abundance showed a high variability between surveys. On the other hand, over the 30 years interval there was little overall change at the between-site level hierarchical structure in the subtidal communities of Maxwell Bay. The sites near the penguin rookery consistently showed the highest biodiversity, indicating the importance of land-based nutrients input in Antarctic coastal habitats. A noticeable pattern change over 30 years was the increase of Desmarestia complex and Plocamium cartilagineum and the decrease of Himantothallus grandifolius. Both groups are still dominant, but the shift from Himantothallus to Desmarestia-Plocamium may reflects temperature rise on the Maxwell Bay coast compared to the past.

Co-production of biodiesel and bioethanol using psychrophilic microalga Chlamydomonas sp. KNM0029C isolated from Arctic sea ice.

BACKGROUND: Biofuels, generated using microalgae as sustainable energy, have received a lot of attention. Microalgae can be cultivated at low cost with CO2 and solar energy without competition from edible crops. Psychrophilic microalgae can be a suitable feedstock to produce biofuels without the environmental constraints of low temperatures, because they can grow below 10 °C. However, there is a lack of efficient strategies using psychrophilic microalgae to produce biodiesel and bioethanol. Therefore, the current study aimed to optimize the production of biodiesel and bioethanol from Arctic Chlamydomonas sp. KNM0029C at low temperatures. RESULTS: After incubation in a 20-L photobioreactor, fatty acid methyl ester (FAME) was extracted using modified FAME extraction methods, producing a maximum yield of 0.16-g FAME/g KNM0029C. Residual biomass was pretreated for bioethanol production, and the yields from different methods were compared. The highest bioethanol yield (0.22-g/g residual biomass) was obtained by pretreatment with enzyme (amyloglucosidase) after sonication. Approximately 300-mg biofuel was obtained, including 156-mg FAME biodiesel and 144-mg bioethanol per g dried cells, representing the highest recorded yield from psychrophilic microalgae. CONCLUSIONS: This is the first to attempt at utilizing biomass from psychrophilic Arctic microalga Chlamydomonas sp. KNM0029C for the co-production of bioethanol and biodiesel, and it yielded the highest values among reported studies using psychrophilic organisms. These results can be used as a source for the efficient biofuel production using polar microalgae.

Nomogram for predicting overall survival in children with neuroblastoma based on SEER database

Purpose@#This study was performed to establish and validate a nomogram for predicting the overall survival in children with neuroblastoma. @*Methods@#The latest clinical data of neuroblastoma in Surveillance, Epidemiology, and End Results (SEER) database was extracted from 2000 to 2016. The cases included were randomly divided into training and validation cohorts. The survival curves were drawn with a Kaplan-Meier estimator to investigate the influences of certain single factors on overall survival. Also, least absolute shrinkage and selection operator regression was applied to further select the prognostic variables for neuroblastoma. Additionally, receiver operating characteristic (ROC) curves and calibration curves were used to evaluate the accuracy of the nomogram. @*Results@#In total, 1,262 patients were collected and 8 independent prognostic factors were achieved, including patients’ age, sex, race, tumor grade, radiotherapy, chemotherapy, tumor site, and tumor size. Then we constructed a nomogram by using the data of the training cohort with 886 cases. Subsequently, the nomogram was validated internally and externally with 886 and 376 cases, respectively. The internal validation revealed that the area under the curves (AUC) of ROC curves of 1-, 3-, and 5-year overall survival were 0.69, 0.78, and 0.81, respectively. Accordingly, the external validation also showed that the AUC of 1-, 3-, and 5-year overall survival were all ≥0.69. Both methods of validation demonstrated that the predictive calibration curves were consistent with standard curves. @*Conclusion@#The nomogram possess the potential to be a new tool in predicting the survival rate of neuroblastoma patients.

Nomogram for predicting overall survival in children with neuroblastoma based on SEER database

Purpose@#This study was performed to establish and validate a nomogram for predicting the overall survival in children with neuroblastoma. @*Methods@#The latest clinical data of neuroblastoma in Surveillance, Epidemiology, and End Results (SEER) database was extracted from 2000 to 2016. The cases included were randomly divided into training and validation cohorts. The survival curves were drawn with a Kaplan-Meier estimator to investigate the influences of certain single factors on overall survival. Also, least absolute shrinkage and selection operator regression was applied to further select the prognostic variables for neuroblastoma. Additionally, receiver operating characteristic (ROC) curves and calibration curves were used to evaluate the accuracy of the nomogram. @*Results@#In total, 1,262 patients were collected and 8 independent prognostic factors were achieved, including patients’ age, sex, race, tumor grade, radiotherapy, chemotherapy, tumor site, and tumor size. Then we constructed a nomogram by using the data of the training cohort with 886 cases. Subsequently, the nomogram was validated internally and externally with 886 and 376 cases, respectively. The internal validation revealed that the area under the curves (AUC) of ROC curves of 1-, 3-, and 5-year overall survival were 0.69, 0.78, and 0.81, respectively. Accordingly, the external validation also showed that the AUC of 1-, 3-, and 5-year overall survival were all ≥0.69. Both methods of validation demonstrated that the predictive calibration curves were consistent with standard curves. @*Conclusion@#The nomogram possess the potential to be a new tool in predicting the survival rate of neuroblastoma patients.

Composition and structure of the marine benthic community in Terra Nova Bay, Antarctica: Responses of the benthic assemblage to disturbances.

The community structure and assemblages of marine benthic organisms were investigated in coastal areas near the Jang Bogo Antarctic Research Station in Terra Nova Bay during the 2012-2018 summer seasons. We also examined the recovery pattern of marine benthic organisms following disturbance due to the construction of the Jang Bogo Station. A total of 26 taxa were identified in the study area during the experimental period. Species number and diversity indices (richness, evenness, and diversity) were relatively low compared to data previously reported from Terra Nova Bay. Sphaerotylus antarcticus, Clavularia frankliniana, Hydractinia sp., Iridaea cordata, Fragilariopsis spp., Alcyonium antarcticum, and Metalaeospira pixelli were the dominant species in this area. Of these, the diatom Fragilariopsis spp. were the most abundant species, indicating their key role in maintaining the marine benthic community and controlling biogeochemical cycling. During the construction of the Jang Bogo Station, sediment coverage increased and diatoms declined due to the release of sediment into the coastal area. In February 2014, one month after the disturbance due to cyclone, the diatom coverage increased dramatically and thereby species number, richness index, and diversity index steadily rose from 2015 to 2018. However, non-metric multidimensional scaling ordination analysis of species similarities among sampling times showed that community structure had not completely recovered by 2018. Thus, long-term monitoring is required to elucidate the post-disturbance settlement mechanisms of marine benthic organisms at the study area in Terra Nova Bay.

Type II Ice-Binding Proteins Isolated from an Arctic Microalga Are Similar to Adhesin-Like Proteins and Increase Freezing Tolerance in Transgenic Plants.

Microalgal ice-binding proteins (IBPs) in the polar region are poorly understood at the genome-wide level, although they are important for cold adaptation. Through the transcriptome study with the Arctic green alga Chloromonas sp. KNF0032, we identified six Chloromonas IBP genes (CmIBPs), homologous with the previously reported IBPs from Antarctic snow alga CCMP681 and Antarctic Chloromonas sp. They were organized with multiple exon/intron structures and low-temperature-responsive cis-elements in their promoters and abundantly expressed at low temperature. The biological functions of three representative CmIBPs (CmIBP1, CmIBP2 and CmIBP3) were tested using in vitro analysis and transgenic plant system. CmIBP1 had the most effective ice recrystallization inhibition (IRI) activities in both in vitro and transgenic plants, and CmIBP2 and CmIBP3 had followed. All transgenic plants grown under nonacclimated condition were freezing tolerant, and especially 35S::CmIBP1 plants were most effective. After cold acclimation, only 35S::CmIBP2 plants showed slightly increased freezing tolerance. Structurally, the CmIBPs were predicted to have ß-solenoid forms with parallel ß-sheets and repeated TXT motifs. The repeated TXT structure of CmIBPs appears similar to the AidA domain-containing adhesin-like proteins from methanogens. We have shown that the AidA domain has IRI activity as CmIBPs and phylogenetic analysis also supported that the AidA domains are monophyletic with ice-binding domain of CmIBPs, and these results suggest that CmIBPs are a type of modified adhesins.

Draft Genome Sequence of Arthrobacter oryzae TNBS02, a Bacterium Containing Heavy Metal Resistance Genes, Isolated from Soil of Antarctica.

Arthrobacter oryzae TNBS02 was isolated from soil at Terra Nova Bay of Victoria Land, Antarctica. The genome consists of a chromosome with 4,248,670 bp which contains a total of 3,994 genes. It was identified that this strain has many heavy metal resistance genes similar to other Arthrobacter strains isolated from contaminated environments.

Lipid Production by Arctic Microalga Chlamydomonas sp. KNF0008 at Low Temperatures.

A lipid-producing microalga, Chlamydomonas sp. KNF0008, collected from the Arctic was capable of growing at temperatures ranging from 4 to 20 °C, and the highest cell density was measured at 15 °C and 100 µmol photons m-2 s-1 light intensity under continuous shaking and external aeration. KNF0008 showed the elevated accumulation of lipid bodies under nitrogen-deficient conditions, rather than under nitrogen-sufficient conditions. Fatty acid production of KNF0008 was 4.2-fold (104 mg L-1) higher than that of C. reinhardtii CC-125 at 15 °C in Bold's Basal Medium. The dominant fatty acids were C16:0, C16:4, C18:1, and C18:3, and unsaturated fatty acids (65.69%) were higher than saturated fatty acids (13.65%) at 15 °C. These results suggested that Arctic Chlamydomonas sp. KNF0008 could possibly be utilized for production of biodiesel during periods of cold weather because of its psychrophilic characteristics.

Mitochondrial and Plastid Genomes from Coralline Red Algae Provide Insights into the Incongruent Evolutionary Histories of Organelles.

Mitochondria and plastids are generally uniparentally inherited and have a conserved gene content over hundreds of millions of years, which makes them potentially useful phylogenetic markers. Organelle single gene-based trees have long been the basis for elucidating interspecies relationships that inform taxonomy. More recently, high-throughput genome sequencing has enabled the construction of massive organelle genome databases from diverse eukaryotes, and these have been used to infer species relationships in deep evolutionary time. Here, we test the idea that despite their expected utility, conflicting phylogenetic signal may exist in mitochondrial and plastid genomes from the anciently diverged coralline red algae (Rhodophyta). We generated complete organelle genome data from five coralline red algae (Lithothamnion sp., Neogoniolithon spectabile, Renouxia sp., Rhodogorgon sp., and Synarthrophyton chejuensis) for comparative analysis with existing organelle genome data from two other species (Calliarthron tuberculosum and Sporolithon durum). We find strong evidence for incongruent phylogenetic signal from both organelle genomes that may be explained by incomplete lineage sorting that has maintained anciently derived gene copies or other molecular evolutionary processes such as hybridization or gene flow during the evolutionary history of coralline red algae.

Genome sequencing of the winged midge, Parochlus steinenii, from the Antarctic Peninsula.

Background: In the Antarctic, only two species of Chironomidae occur naturally-the wingless midge, Belgica antarctica , and the winged midge, Parochlus steinenii . B. antarctica is an extremophile with unusual adaptations. The larvae of B. antarctica are desiccation- and freeze-tolerant and the adults are wingless. Recently, the compact genome of B. antarctica was reported and it is the first Antarctic eukaryote to be sequenced. Although P. steinenii occurs naturally in the Antarctic with B. antarctica , the larvae of P. steinenii are cold-tolerant but not freeze-tolerant and the adults are winged. Differences in adaptations in the Antarctic midges are interesting in terms of evolutionary processes within an extreme environment. Herein, we provide the genome of another Antarctic midge to help elucidate the evolution of these species. Results: The draft genome of P. steinenii had a total size of 138 Mbp, comprising 9513 contigs with an N50 contig size of 34,110 bp, and a GC content of 32.2%. Overall, 13,468 genes were predicted using the MAKER annotation pipeline, and gene ontology classified 10,801 (80.2%) predicted genes to a function. Compared with the assembled genome architecture of B. antarctica , that of P. steinenii was approximately 50 Mbp longer with 6.2-fold more repeat sequences, whereas gene regions were as similarly compact as in B. antarctica . Conclusions: We present an annotated draft genome of the Antarctic midge, P. steinenii . The genomes of P. steinenii and B. antarctica will aid in the elucidation of evolution in harsh environments and provide new resources for functional genomic analyses of the order Diptera.

Enzymatic modification by point mutation and functional analysis of an omega-6 fatty acid desaturase from Arctic Chlamydomonas sp.

Arctic Chlamydomonas sp. is a dominant microalgal strain in cold or frozen freshwater in the Arctic region. The full-length open reading frame of the omega-6 fatty acid desaturase gene (AChFAD6) was obtained from the transcriptomic database of Arctic Chlamydomonas sp. from the KOPRI culture collection of polar micro-organisms. Amino acid sequence analysis indicated the presence of three conserved histidine-rich segments as unique characteristics of omega-6 fatty acid desaturases, and three transmembrane regions transported to plastidic membranes by chloroplast transit peptides in the N-terminal region. The AChFAD6 desaturase activity was examined by expressing wild-type and V254A mutant (Mut-AChFAD6) heterologous recombinant proteins. Quantitative gas chromatography indicated that the concentration of linoleic acids in AChFAD6-transformed cells increased more than 3-fold [6.73 ± 0.13 mg g-1 dry cell weight (DCW)] compared with cells transformed with vector alone. In contrast, transformation with Mut-AChFAD6 increased the concentration of oleic acid to 9.23 ± 0.18 mg g-1 DCW, indicating a change in enzymatic activity to mimic that of stearoyl-CoA desaturase. These results demonstrate that AChFAD6 of Arctic Chlamydomonas sp. increases membrane fluidity by enhancing denaturation of C18 fatty acids and facilitates production of large quantities of linoleic fatty acids in prokaryotic expression systems.

Characterization of Stearoyl-CoA Desaturases from a Psychrophilic Antarctic Copepod, Tigriopus kingsejongensis.

Stearoyl-CoA desaturase is a key regulator in fatty acid metabolism that catalyzes the desaturation of stearic acid to oleic acid and controls the intracellular levels of monounsaturated fatty acids (MUFAs). Two stearoyl-CoA desaturases (SCD, Δ9 desaturases) genes were identified in an Antarctic copepod, Tigriopus kingsejongensis, that was collected in a tidal pool near the King Sejong Station, King George Island, Antarctica. Full-length complementary DNA (cDNA) sequences of two T. kingsejongensis SCDs (TkSCDs) were obtained from next-generation sequencing and isolated by reverse transcription PCR. DNA sequence lengths of the open reading frames of TkSCD-1 and TkSCD-2 were determined to be 1110 and 681 bp, respectively. The molecular weights deduced from the corresponding genes were estimated to be 43.1 kDa (TkSCD-1) and 26.1 kDa (TkSCD-2). The amino acid sequences were compared with those of fatty acid desaturases and sterol desaturases from various organisms and used to analyze the relationships among TkSCDs. As assessed by heterologous expression of recombinant proteins in Escherichia coli, the enzymatic functions of both stearoyl-CoA desaturases revealed that the amount of C16:1 and C18:1 fatty acids increased by greater than 3-fold after induction with isopropyl ß-D-thiogalactopyranoside. In particular, C18:1 fatty acid production increased greater than 10-fold in E. coli expressing TkSCD-1 and TkSCD-2. The results of this study suggest that both SCD genes from an Antarctic marine copepod encode a functional desaturase that is capable of increasing the amounts of palmitoleic acid and oleic acid in a prokaryotic expression system.

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In this study, a new "non-oxytrichid Dorsomarginalia" ciliate, Urosomoida sejongensis n. sp. discovered from freshwater of the King George Island, Antarctica, was investigated using morphological, morphometrical, and molecular methods. Morphology of U. sejongensis is characterized as follows: body shape slender to elongated; cortical granules spherical and colorless, groups of granules formed patchy distribution; ring-shaped structures scattered in cytoplasm; 27-30 adoral membranelles with undulating membranes in Oxytricha pattern; usually 17 frontal-ventral-transverse (FVT) cirri composed of 3 frontal, 1 buccal, 4 frontoventral, 3 postoral ventral, 2 pretransverse ventral and 4 transverse cirri; 1 right and 1 left marginal rows; 3 dorsal kineties with 1 dorsomarginal row, 3 caudal cirri; 1 micronucleus between 2 macronuclear nodules. This new species mainly differs from other congeners by the combination of following morphological features: a micronucleus, cortical granules, and ciliatures (e.g., adoral membranelles, FVT cirri). Urosomoida sejongensis shows a nucleotide similarity of 97.3% with U. agilis, type of this genus, using the SSU rDNA sequence. Molecular phylogeny shows a non-monophyletic relationship among Urosomoida species and emphasizes the need for further morphogenetic studies of this genus and other related species to resolve morphological convergences.