https://repository.kopri.re.kr/handle/201206/15765 Wed, 08 Apr 2026 06:05:55 GMT 2026-04-08T06:05:55Z https://repository.kopri.re.kr/handle/201206/16616 Title: Exogenous abscisic acid enhances freeze-thaw stress tolerance in Antarctic moss Sanionia uncinata through coordinated antioxidant defense and osmoprotectant accumulation Authors: Seo, Suyeon; Ahn, Yong-Yoon; Kim, Kitae; Lee, Jun Hyuck; Min, Kyungwon; Lee, Hyoungseok Abstract: Abscisic acid (ABA) is known to improve plant freeze-thaw stress tolerance (FTST), but its role in Antarctic mosses remains largely unexplored. Accordingly, this study investigated the effects of exogenous ABA application on FTST of gametophore Sanionia uncinata, one of the most widespread moss species in maritime Antarctica. Samples were treated with 10 mu M ABA for 72 h under controlled culture conditions, then subjected to freezing stress at -13 and -16 degrees C. Various physiological parameters were measured to assess ABA-induced FTST, including ion-leakage, photosynthetic efficiency (Fv/Fm), malondialdehyde (MDA) content, compatible solutes/osmolytes (proline and total sugars), and antioxidant enzyme activities, e.g., superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX). Gametophores treated with ABA efficiently assimilated ABA, evident by similar to 20-fold higher than controls. ABA application did not impede gametophore growth but slightly increased dry weight/fresh weight ratio (5 % increase). ABA significantly improved freezing tolerance, reducing freeze-induced membrane injury by similar to 20 % at both stress temperatures, alleviating oxidative stress with 25-34 % lower MDA accumulation, and enhancing PSII maximum quantum yield (Fv/Fm) by 6-7 % following freeze-thaw stress. Improved FTST was paralleled by enhanced activities of antioxidant enzymes, CAT and APX increasing by similar to 11 % and 56 %, respectively, while SOD remained unchanged. ABA treatment also promoted osmoprotectant accumulation, with proline content increasing by 33.5 % and total soluble sugars nearly doubling (99 % increase). These findings provide the first quantitative evidence that exogenous ABA markedly improves FTST in an Antarctic moss through coordinated antioxidant defense and osmoprotectant accumulation, highlighting ABA as a critical regulator of stress resilience in S. uncinata. Mon, 01 Dec 2025 00:00:00 GMT https://repository.kopri.re.kr/handle/201206/16616 2025-12-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/16580 Title: Identification and characterization of a novel, low-temperature-active GH8 endo-β-1,4-glucanase exhibiting broad pH stability from Antarctic Glacieibacterium sp. PAMC 29367 Authors: Do Young Kim; Lee, Yung Mi; Jong Suk Lee; Hyangmi Kim; Chung-Wook Chung Abstract: Endo-β-1,4-glucanase plays an essential role in the breakdown of cellulosic substances that consist of D-glucose units linked by β-1,4-glycosidic bonds. In this work, the gene encoding a novel extracellular glycoside hydrolase (GH) family 8 endo-β-1,4-glucanase (GluS) from Glacieibacterium sp. PAMC 29367, an Antarctic lichen (Megaspora verrucosa)-associated bacterial species, was identified, cloned, and characterized. The GluS gene (1080-bp) was predicted to express a non-modular endo-β-1,4-glucanase (38,347 Da) that possesses a single catalytic GH8 domain, showing 65.5% amino acid sequence identity with an uncharacterized endoglucanase from Alphaproteobacteria bacterium (GenBank accession number: PZN92894). Recombinant endo-β-1,4-glucanase proteins (rGluS: 39.0 kDa) produced in Escherichia coli BL21 exhibited the highest carboxymethylcellulose (CMC)-degrading activity at pH 5.0 and 40°C, while maintaining over 80% of maximal endo-β-1,4-glucanase activity even at 25°C. Furthermore, the enzyme exhibited notable stability across a broad pH range from 4.5 to 10.0. rGluS activity was greatly stimulated by >1.3-fold in the presence of 1 mM Co2+, whereas it was nearly completely inhibited by 0.5% sodium dodecyl sulfate or 5 mM N-bromosuccinimide. The specific activity (31.1 U mg？1) and kcat/Km (11.02 mg？1 s？1 mL) values of rGluS for CMC were marginally greater than those for barley β-1,3-1,4-glucan, with a specific activity of 28.9 U mg？1 and kcat/Km of 8.79 mg？1 s？1 mL for barley β-1,3-1,4-glucan. The recombinant enzyme demonstrated no detectable biocatalytic activity for p-nitrophenylglucopyranoside, p-nitrophenylcellobioside, D-cellobiose, and D-cellotriose, while it could cleave D-cellotetraose to generate two molecules of D-cellobiose. Moreover, rGluS-mediated degradation of D-cellopentaose led mainly to D-cellobiose production along with D-glucose and D-cellotriose, while its hydrolysis of CMC yielded D-cellotriose as the dominant end product, accompanied by D-glucose, D-cellobiose and D-cellotetraose. The substrate preferences and degradation profiles of rGluS on cellulosic materials supported its classification as a true GH8 endo-acting β-1,4-glucanase without transglycosylation activity. The findings of this study suggest that rGluS represents a novel, highly active, cold-adapted GH8 endo-β-1,4-glucanase exhibiting broad pH stability, and may serve as an effective candidate for low-temperature processing in the food and textile industries. Wed, 01 Oct 2025 00:00:00 GMT https://repository.kopri.re.kr/handle/201206/16580 2025-10-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/16130 Title: Genetic isolation and metabolic complexity of an Antarctic subglacial microbiome Authors: Hwang, Kyuin; Kim, Kyung Mo; Lee, Hanbyul; Cho, Ahnna; Davis Christina L.; Christner Brent C.; Priscu John C.; Kim, Ok-Sun Abstract: Microbes inhabiting and evolving in aquatic ecosystems beneath polar ice sheets subsist under energy-limited conditions while in relative isolation from surface gene pools and their common ancestral populations of origin. Samples obtained from beneath West Antarctic Ice Sheet (WAIS) allowed us to examine evolutionary relationships of and identify metabolic pathways in microbial genomes recovered from the Mercer Subglacial Lake (SLM) ecosystem. We obtained 1,374 single-cell amplified genomes (SAGs) from individual bacterial and archaeal cells that were isolated from samples of SLM's water column and sediments. These genomes reveal that a diversity of microorganisms including Patescibacteria exists in SLM. Comparative analyses show that most genomes correspond to new species and taxonomic groups, with phylogenomic and functional evidence supporting their genetic isolation from marine and surface biomes. Genomic data reveal diverse metabolisms in SLM that are capable of oxidizing organic and inorganic compounds via aerobic or anaerobic respiration. Distinct metabolic guild structures are observed for the subglacial populations, where trophic shifts from organotrophy to chemolithotrophy may depend on oxygen availability. Our SAG data suggest versatile metabolic capabilities in the characterized microbial assemblage, reveal key energy-generating strategies in the subglacial aquatic ecosystem, and provide a framework to assess microbial evolution beneath WAIS. Fri, 01 Aug 2025 00:00:00 GMT https://repository.kopri.re.kr/handle/201206/16130 2025-08-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/16088 Title: Comparative Metabolite Profiling of Antarctic and Korean Mosses: Insights into Adaptation Mechanisms of Antarctic Moss Species Authors: Naznin Marufa; Mahmood Raisul Awal; Alam Md Badrul; Shin, Kil Ho; Min, Kyungwon; Lee, Sang-Han; Lee, Hyoungseok; Kim, Sunghwan Abstract: This study investigates the relationship between secondary metabolites and stress tolerance in moss species, with a specific emphasis on comparing Antarctic and Korean mosses. Analyses of total phenolic content (TPC) and total flavonoid content (TFC) revealed that Antarctic mosses contain these compounds at significantly higher levels compared to the Korean mosses. These findings are consistent with greater antioxidant activities observed in Antarctic mosses through DPPH and ABTS？+ radical scavenging assays. In this study, a total of 620 metabolites were identified from the moss samples. The results showed that Antarctic mosses exhibited a high number and diversity of compounds including terpenoids, flavonoids, lipids, and other classes. Additionally, Antarctic mosses had fewer lipids with carbon chain lengths below 18 and a higher content of unsaturated lipids, indicating adaptations to maintain membrane fluidity under cold stress. The phylogenetic relationships suggested a correlation between metabolite profiles and genetic adaptations between these species. This research highlights the complex biochemical strategies that mosses, particularly those in Antarctic regions, employ to adapt the environmental stressors. The high abundance of secondary metabolites in Antarctic mosses not only serves as a defense mechanism against oxidative stress but also suggests their potential applications in various biotechnological aspects. This study reveals new avenues for exploring the ecological roles and potential uses of these resilient plant species. Tue, 01 Jul 2025 00:00:00 GMT https://repository.kopri.re.kr/handle/201206/16088 2025-07-01T00:00:00Z