Production and waste treatment of polyesters: application of bioresources and biotechniques.

Chemical resources and techniques have long been used in the history of bulk polyester production and still dominate today's chemical industry. The sustainable development of the polyester industry demands more renewable resources and environmentally benign polyester products. Accordingly, the rapid development of biotechnology has enabled the production of an extensive range of aliphatic and aromatic polyesters from renewable bio-feedstocks. This review addresses the production of representative commercial polyesters (polyhydroxyalkanoates, polylactic acid, poly ε-caprolactone, polybutylene succinate, polyethylene terephthalate, polybutylene terephthalate, polypropylene terephthalate, polyethylene furandicarboxylate, polypropylene furandicarboxylate, and polybutylene furandicarboxylate) or their monomers (lactic acid, succinic acid, 1,4-butanediol, ethylene glycol, terephthalic acid, 1,3-propanediol, and 2,5-furandicarboxylic acid) from renewable bioresources. In addition, this review summarizes advanced biotechniques in the treatment of polyester wastes, representing the near-term trends and future opportunities for waste-to-value recycling and the remediation of polyester wastes under sustainable models. For future prospects, it is essential to further expand: non-food bioresources, optimize bioprocesses and biotechniques in the preparation of bioderived or biodegradable polyesters with promising: material performance, biodegradability, and low production cost.

Do trace metal(loid)s in road soils pose health risks to tourists? A case of a highly-visited national park in China.

Nowadays, more people tend to spend their recreational time in large national parks, and trace metal(loid)s in soils have attracted long-term attention due to their possible harm to human health. To investigate the pollution levels, potential sources and health risks of trace metal(loid)s in road soils, a total of eight trace metal(loid)s (including As, Cd, Cr, Cu, Ni, Pb, Zn and Hg) from 47 soil samples along roads were studied in the Huangshan National Park in Southeast China. The results showed that the concentrations of As, Cd, Pb, Zn and Hg appeared different degrees of pollution compared with their corresponding background values. According to the pollution indices, Hg and Cd were recognized as significant pollutants presenting moderate to high ecological risk. Combining principal component analysis and positive matrix factorization model, the results showed that traffic, industrial, agricultural and natural sources were the potential origins of trace metal(loid)s in this area, with contribution rates of 39.93%, 25.92%, 10.53% and 23.62%, respectively. Non-carcinogenic risks were all negligible, while the carcinogenic risk of As was higher than the limit (1 × 10-6). Moreover, children were more susceptible to trace metal(loid)s by ingestion which appeared to be a more important exposure pathway than dermal contact and inhalation. The contribution rates of different sources to non-carcinogenic risks and carcinogenic risks were similar among children and adults, while traffic and industrial sources have a significant impact on health risks. This study will give more insights to control the environmental risks of trace metal(loid)s in national parks.

Hop bitter acids: resources, biosynthesis, and applications.

Diversified members of hop bitter acids (α- and ß-acids) have been found in hop (Humulus lupulus). Mixtures of hop bitter acids have been traditionally applied in brewing and food industries as bitterness flavors or food additives. Recent studies have discovered novel applications of hop bitter acids and their derivatives in medicinal and pharmaceutical fields. The increasing demands of purified hop bitter acid promoted biosynthesis efforts for the heterologous biosynthesis of objective hop bitter acids by engineered microbial factories. In this study, the updated information of hop bitter acids and their representative application in brewing, food, and medicine fields are reviewed. We also speculate future trends on the development of robust microbial cell factories and biotechnologies for the biosynthesis of hop bitter acids. KEY POINTS: • Structures and applications of hop bitter acids are summarized in this study. • Biosynthesis of hop bitter acids remains challenging. • We discuss potential strategies in the microbial production of hop bitter acids.

Generation, identification, and functional analysis of monoclonal antibodies against porcine epidemic diarrhea virus nucleocapsid.

The variant strains of porcine epidemic diarrhea virus (PEDV) severely threaten the pig industry worldwide and cause up to 100% mortality in suckling piglets. It is critically important and urgent to develop tools for detection of PEDV infection. In this study, we developed six monoclonal antibodies (mAbs) targeting N protein of PEDV and analyzed their applications on enzyme-linked immunosorbent assay (ELISA), indirect immunofluorescence assay (IFA), western blot assay, and flow cytometry assay. The results demonstrated that all these six mAbs were IgG1 isotype and κ chain. Among these six mAbs, 3F12 recognizes a linear epitope (VAAVKDALKSLGI) while the other five mAbs recognize different conformational epitopes formed by a specific peptide fragment or the full length of N protein. The functional analysis showed that all these six mAbs were applicable to ELISA, western blot, IFA, and flow cytometry assay. In conclusion, we developed six mAbs against PEDV-N protein to facilitate the early detection of PEDV infection using ELISA, western blot, IFA, and flow cytometry.

DCLK1 and its oncogenic functions: A promising therapeutic target for cancers.

Doublecortin-like kinase 1 (DCLK1), a significant constituent of the protein kinase superfamily and the doublecortin family, has been recognized as a prooncogenic factor that exhibits a strong association with the malignant progression and clinical prognosis of various cancers. DCLK1 serves as a stem cell marker that governs tumorigenesis, tumor cell reprogramming, and epithelial-mesenchymal transition. Multiple studies have indicated the capable of DCLK1 in regulating the DNA damage response and facilitating DNA damage repair. Additionally, DCLK1 is involved in the regulation of the immune microenvironment and the promotion of tumor immune evasion. Recently, DCLK1 has emerged as a promising therapeutic target for a multitude of cancers. Several small-molecule inhibitors of DCLK1 have been identified. Nevertheless, the biological roles of DCLK1 are mainly ambiguous, particularly with the disparities between its α- and ß-form transcripts in the malignant progression of cancers, which impedes the development of more precisely targeted drugs. This article focuses on tumor stem cells, tumor epithelial-mesenchymal transition, the DNA damage response, and the tumor microenvironment to provide a comprehensive overview of the association between DCLK1 and tumor malignant progression, address unsolved questions and current challenges, and project future directions for targeting DCLK1 for the diagnosis and treatment of cancers.

Discovery of Highly Potent Small-Molecule PD-1/PD-L1 Inhibitors with a Novel Scaffold for Cancer Immunotherapy.

Inhibition of the PD-1/PD-L1 interaction through small-molecule inhibitors is a promising therapeutic approach in cancer immunotherapy. Herein, we utilized BMS-202 as the lead compound to develop a series of novel PD-1/PD-L1 small-molecule inhibitors with a naphthyridin scaffold. Among these compounds, X14 displayed the most potent inhibitory activity for the PD-1/PD-L1 interaction (IC50 = 15.73 nM). Furthermore, X14 exhibited good binding affinity to both human PD-L1 (KD = 14.62 nM) and mouse PD-L1 (KD = 392 nM). In particular, X14 showed favorable pharmacokinetic properties (oral bioavailability, F = 58.0%). In the 4T1 (mouse breast cancer cells) syngeneic mouse model, intragastric administration of X14 at 10 mg/kg displayed significant antitumor efficacy (TGI = 66%). Mechanistic investigations revealed that X14 effectively enhanced T-cell infiltration within the tumor microenvironment. Our study demonstrates that compound X14 exhibits potential as a candidate compound for the development of orally effective small-molecule inhibitors targeting PD-1/PD-L1.

Arsenophonus Interacts with Buchnera to Improve Growth Performance of Aphids under Amino Acid Stress.

Amino acids play a crucial role in the growth and development of insects. Aphids cannot ingest enough amino acids in plant phloem to meet their requirements, and therefore, they are mainly dependent on the obligate symbiont Buchnera aphidicola to synthesize essential amino acids. Besides Buchnera, aphids may harbor another facultative symbiont, Arsenophonus, which alters the requirement of the cotton-melon aphid Aphis gossypii for amino acid. However, it is unclear how Arsenophonus regulates the requirement. Here, we found that Arsenophonus ameliorated growth performance of A. gossypii on an amino acid-deficient diet. A deficiency in lysine (Lys) or methionine (Met) led to changes in the abundance of Arsenophonus. Arsenophonus suppressed the abundance of Buchnera when aphids were fed a normal amino acid diet, but this suppression was eliminated or reversed when aphids were on a Lys- or Met-deficient diet. The relative abundance of Arsenophonus was positively correlated with that of Buchnera, but neither of them was correlated with the body weight of aphids. The relative expression levels of Lys and Met synthase genes of Buchnera were affected by the interaction between Arsenophonus infections and Buchnera abundance, especially in aphids reared on a Lys- or Met-deficient diet. Arsenophonus coexisted with Buchnera in bacteriocytes, which strengthens the interaction. IMPORTANCE The obligate symbiont Buchnera can synthesize amino acids for aphids. In this study, we found that a facultative symbiont, Arsenophonus, can help improve aphids' growth performance under amino acid deficiency stress by changing the relative abundance of Buchnera and the expression levels of amino acid synthase genes. This study highlights the interaction between Arsenophonus and Buchnera to ameliorate aphid growth under amino acid stress.

Column study of Cd(II) removal and longevity by nitrate-mediated zero-valent iron with mixed anaerobic microorganisms.

In this study, hydrogen-autotrophic microorganisms and zero-valent iron (Fe0) were filled into columns to investigate hydrogenotrophic denitrification effect on cadmium (Cd(II)) removal and column life-span with sand, microorganisms, Fe0 and bio-Fe0 columns as controls. In terms of the experiment results, the nitrate-mediated bio-Fe0 column showed a slow Cd(II) migration rate of 0.04 cm/PV, while the values in the bio-Fe0 and Fe0 columns were 0.06 cm/PV and 0.14 cm/PV respectively, indicating much higher Cd(II) removal efficiency and longer service life of the nitrate-mediated bio-Fe0 column. The XRD and SEM-EDX results implied that this improvement was attributed to hydrogenotrophic denitrification that caused more serious iron corrosion and larger amount of secondary mineral generation (e.g., green rust, lepidocrocite and goethite). These active minerals provided more reaction sites for Cd(II) adsorption and further immobilization. In addition, the decrease of Cd(II) migration front and the increase of removal capacity along the bio-Fe0 column mediated by nitrate presented an uneven distribution in reactive zone. The latter half part was identified to be a more active region for Cd(II) immobilization. The above results indicate that the introduction of nitrate and microorganisms will improve the performance of iron-based permeable reactive barriers for the remediation of Cd(II)-containing groundwater.

Determination of priority control factors for the management of soil trace metal(loid)s based on source-oriented health risk assessment.

Trace metal(loid)s (TMs) in soils can seriously threaten the ecological environment and human health. With the limitation of resources and costs, determining priority control factor is critical for managing soil TM pollution. To explore the pollution characteristics, source apportionment, and human health risk of TMs, a total of 209 surface soil samples were collected from Anqing City, China. Results showed that all the average values of TM concentration, except for Cr, were higher than their corresponding background value. Using a Positive matrix factorization model coupled with Correlation analysis, four sources (including agricultural sources, atmospheric deposition sources, industrial sources, and natural sources) were identified as the determinants for the accumulation of soil TMs, with the contribution rates of 12.4%, 8.1%, 64.1%, and 15.4%, respectively. The assessment of probabilistic health risks revealed that Non- carcinogenic risks of all populations were acceptable (HI < 1), while Carcinogenic risks were all at a high level (TCR > 10E-04). Agricultural pollution and As were identified as priority control factors, according to the analysis results of the relationship among TMs, pollution sources and health risks. Our findings provide scientific support for decision-makers to formulate target control policies and reduce management costs of soil pollution.

Differential expression and regulation of iron-regulated metal transporters in Arabidopsis halleri and Arabidopsis thaliana--the role in zinc tolerance.

To avoid zinc (Zn) toxicity, plants have developed a Zn homeostasis mechanism to cope with Zn excess in the surrounding soil. In this report, we uncovered the difference of a cross-homeostasis system between iron (Fe) and Zn in dealing with Zn excess in the Zn hyperaccumulator Arabidopsis halleri ssp. gemmifera and nonhyperaccumulator Arabidopsis thaliana. Arabidopsis halleri shows low expression of the Fe acquisition and deficiency response-related genes IRT1 and IRT2 compared with A. thaliana. In A. thaliana, lowering the expression of IRT1 and IRT2 through the addition of excess Fe to the medium increases Zn tolerance. Excess Zn induces significant Fe deficiency in A. thaliana and reduces Fe accumulation in shoots. By contrast, the accumulation of Fe in shoots of A. halleri was stable under various Zn treatments. Root ferric chelate reductase (FRO) activity and expression of FIT are low in A. halleri compared with A. thaliana. Overexpressing a ZIP family member IRT3 in irt1-1, rescues the Fe-deficient phenotype. A fine-tuned Fe homeostasis mechanism in A. halleri maintains optimum Fe level by Zn-regulated ZIP transporters and prevents high Zn uptake through Fe-regulated metal transporters, and in part be responsible for Zn tolerance.

Toxic effects and mechanisms of PFOA and its substitute GenX on the photosynthesis of Chlorella pyrenoidosa.

Perfluorooctanoic acid (PFOA) and its substitute GenX are toxic chemicals that are widespread in the aquatic environment. However, there is little information about their toxicity mechanisms to aquatic organisms. In this study, Chlorella pyrenoidosa (C. pyrenoidosa) was treated with two concentrations (100 ng L-1 and 100 µg L-1) of PFOA or GenX for 12 days. The results showed that these two concentrations of PFOA and GenX began to inhibit the growth of algae after 6 days of treatment, and the Chlorophyll content and photosynthetic activity of C. pyrenoidosa were also negatively affected by these two chemicals. The transcriptomic results indicated that most of the genes related to the photosynthetic metabolism of C. pyrenoidosa were down-regulated (in 100 ng L-1 treatment groups) on the 12th day. Besides, GenX and PFOA showed similar effects on algae photosynthesis including physical damage and metabolic disorders. According to this study, GenX might not be an ideal substitute for PFOA, and more attention should be paid on the management of emerging perfluoroalkyl substances.

Health risk assessment of heavy metal(loid)s in park soils of the largest megacity in China by using Monte Carlo simulation coupled with Positive matrix factorization model.

Urban Parks are important places for residents to engage in outdoor activities, and whether heavy metal(loid)s (HMs) in park soils are harmful to human health has aroused people's concern. A total of 204 topsoil samples containing nine HMs were collected from 78 urban parks of Shanghai in China, and used to assess the health risks caused by HMs in soils. The results revealed that the Hg, Cd and Pb were the main enriched pollutants and posed higher ecological risks than the other HMs. Four HM sources (including natural sources, agricultural activities, industrial production and traffic emissions) were identified by combining the Positive matrix factorization model and Correlation analysis, with the contribution rate of 48.24%, 7.03%, 13.04% and 31.69%, respectively. The assessment of Probabilistic health risks indicated that the Non-carcinogenic risks for all populations were negligible. However, the Total carcinogenic risk cannot be negligible and children were more susceptible than adults. The assessment results of source-oriented health risks showed that industrial production and traffic emissions were estimated to be the most important anthropogenic sources of health risks for all populations. Our results provide scientific support needed for the prevention and control of HM pollution in urban parks.

Preparation, identification, and functional analysis of monoclonal antibodies against atypical porcine pestivirus NS3 protein.

Atypical porcine pestivirus (APPV) had been detected in many countries. However, to date, a commercial detection kit is not available because of a lack of specific monoclonal antibodies (mAbs) to APPV. We generated 7 mAbs targeting the NS3 protein of APPV. Isotyping results indicated that all of these mAbs are IgG1 with a kappa light chain. We analyzed the epitopes recognized by mAbs 2B6, 6G11, 8D1, 8D3, and 8F12, which recognized the same linear epitope (GRIKSAYSDE); the 6H3 and 7E10 mAbs recognized 2 different conformational epitopes. Applications of these antibodies were verified by ELISA, western blot, indirect immunofluorescence assay, and flow cytometry. The antibodies were functionally workable for these immunoassays except for 8F12, which could not be used in flow cytometry.

Effects of seepage velocity and concentration on chromium(VI) removal in abiotic and biotic iron columns.

Continuous-flow iron and bio-iron columns were used to evaluate the effects of seepage velocity and concentration on Cr(VI) removal from groundwater. Solid-phase analysis showed that microorganisms accelerated iron corrosion by excreting extracellular polymeric substances and generated highly reactive minerals containing Fe(II), which gave the bio-iron column a longer life span and enhanced capacity for Cr(VI) removal via enhanced adsorption and reduction by reactive minerals. The bio-iron column showed much higher Cr(VI) removal capacity than the iron column with increasing Cr(VI) loading, which was obtained by increasing the seepage velocity or influent Cr(VI) concentration from 95 to 1138 m yr-1 and from 5 to 40 mg L-1 , respectively. When the Cr(VI) loading varied in a range of 0 to 10 mg L-1 h-1 , the bio-iron column had a 60% longer longevity and one- to sixfold higher Cr(VI) elimination capacity than the iron column. This result indicated that, under fluctuating hydraulic conditions [e.g., seepage velocity and Cr(VI) concentration], the presence of microorganisms can significantly boost Cr(VI) removal using Fe0 -based permeable reactive barriers.

Risk Assessment and Source Apportionment of Soil Heavy Metals under Different Land Use in a Typical Estuary Alluvial Island.

Understanding the environmental risks of soil heavy metals (HMs) and identifying their main sources are the essential prerequisites for the prevention and management of soil pollution. Based on a detailed survey of soil HMs (Cu, Cr, Ni, Zn, Pb, Cd, As and Hg) from different land use types (including agricultural land, construction land, wetland, and forest land) in an estuary alluvial island, the environmental risk and source apportionment of soil HMs were investigated. Altogether, 117 soil samples were taken in the study area to appraise the soil HMs environmental risk by using the geo-accumulation index (Igeo), potential ecological risk index (RI), and human health risk assessment (HRA) and to identify its main sources by using positive matrix factorization (PMF) model. The average concentrations of soil HMs (except As) surpassed their reference background values in China. There were no significant differenced in the mean concentrations of HMs in different land use types, except that the Hg concentration in the construction land was significantly higher than that in others. The results of Igeo showed that Cd pollution was unpolluted to moderately polluted, and that the others were unpolluted. The potential ecological risk level for Cd and Hg was "moderated potential risk", while for Cu, Cr, Ni, Zn, Pb and As was "low potential risk". Higher contamination was distributed at the west-central area. The results of the HRA indicated that the non-carcinogenic risk and the carcinogenic risk that human beings suffered from HMs in different land uses were insignificant. To more accurately identify the sources of soil HMs, the PMF model coupled with the GIS-spatial analysis was applied. The results showed that agricultural activities, natural source, industrial discharge and river transportation, and atmosphere deposition were the main determining factors for the accumulation of soil HMs in the study area, with the contribution rate of 24.25%, 23.79%, 23.84%, and 28.12%, respectively. The study provides an underlying insight needed to control of the soil HM pollutions for an estuary alluvial island.

The Preparation and Biomedical Application of Biopolyesters.

Biopolyesters represent a large family that can be obtained by polymerization of variable bio-derived hydroxyalkanoic acids. The monomer composition, molecular weight of the biopolyesters can affect the properties and applications of the polyesters. The majority of biopolyesters can either be biosynthesized from natural biofeedstocks or semi-synthesized (biopreparation of monomers followed by the chemical polymerization of the monomers). With the fast development of synthetic biology and biosynthesis techniques, the biosynthesis of unnatural biopolyesters (like lactate containing and aromatic biopolyesters) with improved performance and function has been a tendency. The presence of novel preparation methods, novel monomer composition has also significantly affected the properties, functions and applications of the biopolyesters. Due to the properties of biodegradability and biocompatibility, biopolyesters have great potential in biomedical applications (as implanting or covering biomaterials, drug carriers). Moreover, biopolyesters can be fused with other functional ingredients to achieve novel applications or improved functions. This study summarizes and compares the updated preparation methods of representative biopolyesters, also introduces the current status and future trends of their applications in biomedical fields.

Nitrate mediated biotic zero valent iron corrosion for enhanced Cd(II) removal.

In this study, nitrate mediated biotic zero-valent iron (Fe0) corrosion was employed to enhance cadmium (Cd) removal from groundwater. In comparison with a 17.5% Cd(II) removal treated with abiotic Fe0, a 3.9 times higher Cd(II) removal of 86.2% was recorded in the nitrate-mediated biotic Fe0 system. Solids phase characterization confirmed that biogenic minerals such as green rust and iron sulfide could be formed in the nitrate-amended biotic Fe0 system, offering large amount of adsorption sites for Cd(II) removal. The decrease of nitrate concentration and the competition with cathodic hydrogen for biological nitrate reduction by extra organic substance such as sodium acetate both showed significant inhibition on Cd(II) removal, further proving that hydrogenotrophic denitrification was the main mechanism for enhanced Cd(II) removal. Besides, a relatively high Cd(II) removal efficiency was observed over a pH range of 5-8, and it increased with declining pH values. These results demonstrated that the bio-amended iron corrosion technology coupled Fe0-assisted H2 production with hydrogenotrophic denitrification exhibited excellent Cd(II) removal capacity, which enabled this technology a promising potential for Cd(II)-contaminated groundwater treatment and an alternative strategy for Cd(II) and nitrate co-contaminated groundwater remediation.

Arabidopsis IRT3 is a zinc-regulated and plasma membrane localized zinc/iron transporter.

ZIP transporters (ZRT, IRT-like proteins) are involved in the transport of iron (Fe), zinc (Zn) and other divalent metal cations. The expression of IRT3, a ZIP transporter, is higher in the Zn/cadmium (Cd) hyperaccumulator Arabidopsis halleri than is that of its ortholog in Arabidopsis thaliana, which implies a positive association of its expression with Zn accumulation in A. halleri. IRT3 genes from both A. halleri and A. thaliana functionally complemented the Zn uptake mutant Spzrt1 in Schizosaccharomyces pombe; and Zn uptake double mutant zrt1zrt2, Fe-uptake mutant fet3fet4 and conferred Zn and Fe uptake activity in Saccharomyces cerevisiae. By contrast, the manganese (Mn) uptake mutant smf1 phenotypes were not rescued. Insufficient Cd uptake for toxicity was found. Expression of IRT3-green fluorescent protein (GFP) fusion proteins in Arabidopsis root protoplasts indicated localization of both IRT3 proteins in the plasma membrane. Overexpressing AtIRT3 in A. thaliana led to increased accumulation of Zn in the shoot and Fe in the root of transgenic lines. Therefore, IRT3 functions as a Zn and Fe-uptake transporter in Arabidopsis.

Powerdress as the novel regulator enhances Arabidopsis seeds germination tolerance to high temperature stress by histone modification of SOM locus.

Seeds germination or dormancy is strictly controlled by endogenous phytohormone signal and environment cues. High temperature (HT) suppresses seeds germination or triggers seeds dormancy but underlying mechanism by which HT mediates seeds germination thermoinhibition needs more investigating. SOM is reported as the critical factor negatively controls light-irradiation seeds germination by altering Abscisic acid (ABA) and gibberellin acid (GA) biosynthesis. Here we found that HT accelerates SOM expressing through ABA signal transduction component ABI3, both of abi3 and som mutants seeds show high germination rate under HT in contrast to wild type seeds. Using ABI3 as the bait, we identified the epigenetic factor Powerdress (PWR) as the ABI3 interaction protein. Genetic and physiological analysis showed that PWR negatively control the expressing of SOM, and overexpressing PWR enhanced, while pwr mutant reduced, seeds germination thermotolerance. Without HT stress, PWR accelerated the histone H3 deacetylation level and H2A.Z deposition at SOM locus, and thus suppressed ABI3-dependent SOM transcription for seeds germination, HT stress block PWR transcriptional level, thus attenuated the inhibition effect of PWR on SOM expressing, resulting into seeds germination thermoinhibition. Thus our finding propose a new function of PWR in controlling seeds germination under HT through histone acetylation modification and H2A.Z deposition.

The hydrogen sulfide signal enhances seed germination tolerance to high temperatures by retaining nuclear COP1 for HY5 degradation.

Seed germination is a critical stage during the initiation of the plant lifecycle and is strongly affected by endogenous phytohormones and environmental stress. High temperature (HT) upregulates endogenous abscisic acid (ABA) to suppress seed germination, and ABA-INSENSITIVE 5 (ABI5) is the key positive regulator in the ABA signal-mediated modulation of seed germination. In plants, hydrogen sulfide (H2S) is a small gas messenger that participates in multiple physiological processes, but its role in seed germination thermotolerance has not been thoroughly elucidated to date. In this study, we found that H2S enhanced the seed germination rate under HT. Moreover, HT accelerates the efflux of the E3 ligase CONSTITUTIVE PHOTOMORPHOGENESIS 1 (COP1) from the nucleus to the cytoplasm, which results in increased nuclear accumulation of ELONG HYPCOTYL 5 (HY5) to activate the expression of ABI5 and thereby suppress seed germination. However, the H2S signal reversed the HT effect, as characterized by increased COP1 in the nucleus, which resulted in increased degradation of HY5 and reduced expression of ABI5 and thereby enhanced the seed germination thermotolerance. Thus, our findings reveal a novel role for the H2S signal in the modulation of seed germination thermotolerance through the nucleocytoplasmic partitioning of COP1 and the downstream HY5 and ABI5 pathways.