The MKK3-MPK7 cascade phosphorylates ERF4 and promotes its rapid degradation to release seed dormancy in Arabidopsis.

Seeds establish dormancy to delay germination until the arrival of a favorable growing season. In this study, we identify a fate switch comprised of the MKK3-MPK7 kinase cascade and the ethylene response factor ERF4 that is responsible for the seed state transition from dormancy to germination. We show that dormancy-breaking factors activate the MKK3-MPK7 module, which affects the expression of some α-EXPANSIN (EXPA) genes to control seed dormancy. Furthermore, we identify a direct downstream substrate of this module, ERF4, which suppresses the expression of these EXPAs by directly binding to the GCC boxes in their exon regions. The activated MKK3-MPK7 module phosphorylates ERF4, leading to its rapid degradation and thereby releasing its inhibitory effect on the expression of these EXPAs. Collectively, our work identifies a signaling chain consisting of protein phosphorylation, degradation, and gene transcription , by which the germination promoters within the embryo sense and are activated by germination signals from ambient conditions.

Histone Modification and Chromatin Remodeling During the Seed Life Cycle.

Seeds are essential for the reproduction and dispersion of spermatophytes. The seed life cycle from seed development to seedling establishment proceeds through a series of defined stages regulated by distinctive physiological and biochemical mechanisms. The role of histone modification and chromatin remodeling in seed behavior has been intensively studied in recent years. In this review, we summarize progress in elucidating the regulatory network of these two kinds of epigenetic regulation during the seed life cycle, especially in two model plants, rice and Arabidopsis. Particular emphasis is placed on epigenetic effects on primary tissue formation (e.g., the organized development of embryo and endosperm), pivotal downstream gene expression (e.g., transcription of DOG1 in seed dormancy and repression of seed maturation genes in seed-to-seedling transition), and environmental responses (e.g., seed germination in response to different environmental cues). Future prospects for understanding of intricate interplay of epigenetic pathways and the epigenetic mechanisms in other commercial species are also proposed.

Sdr4 dominates pre-harvest sprouting and facilitates adaptation to local climatic condition in Asian cultivated rice.

Pre-harvest sprouting (PHS), which reduces grain yield and quality, is controlled by seed dormancy genes. Because few dormancy-related genes have been cloned, the genetic basis of seed dormancy in rice (Oryza sativa L.) remains unclear. Here, we performed a genome-wide association study and linkage mapping to dissect the genetic basis of seed dormancy in rice. Our findings suggest that Seed Dormancy4 (Sdr4), a central modulator of seed dormancy, integrates the abscisic acid and gibberellic acid signaling pathways at the transcriptional level. Haplotype analysis revealed that three Sdr4 alleles in rice cultivars already existed in ancestral Oryza rufipogon accessions. Furthermore, like the semi-dwarf 1 (SD1) and Rc loci, Sdr4 underwent selection during the domestication and improvement of Asian cultivated rice. The distribution frequency of the Sdr4-n allele in different locations in Asia is negatively associated with local annual temperature and precipitation. Finally, we developed functional molecular markers for Sdr4, SD1, and Rc for use in molecular breeding. Our results provide clues about the molecular basis of Sdr4-regulated seed dormancy. Moreover, these findings provide guidance for utilizing the favorable alleles of Sdr4 and Rc to synergistically boost PHS resistance, yield, and quality in modern rice varieties.

A Local D4h Symmetric Dysprosium(III) Single-Molecule Magnet with an Energy Barrier Exceeding 2000†K*.

Three six-coordinate DyIII single-molecule magnets (SMMs) [Dy(Ot Bu)2 (L)4 ]+ with local D4h symmetry are obtained by optimizing the equatorial ligands. One of the compounds with L=4-phenylpyridine shows an energy barrier (Ueff ) of 2075(11) K, which is the third largest Ueff , and the first Ueff >2000 K for SMMs with axial-type symmetry so far. Ab initio analysis indicates that the exceptional uniaxial magnetic anisotropy is deeply related to the axially compressed octahedral geometry. This work provides a new insight into the local D4h symmetry for high-performance SMMs.

Genetic Dissection of Seed Storability and Validation of Candidate Gene Associated with Antioxidant Capability in Rice (Oryza sativa L.).

Seed storability, defined as the ability to remain alive during storage, is an important agronomic and physiological characteristic, but the underlying genetic mechanism remains largely unclear. Here, we report quantitative trait loci (QTLs) analyses for seed storability using a high-density single nucleotide polymorphism linkage map in the backcross recombinant inbred lines that was derived from a cross of a japonica cultivar, Nipponbare, and an indica cultivar, 9311. Seven putative QTLs were identified for seed storability under natural storage, each explaining 3.6-9.0% of the phenotypic variation in this population. Among these QTLs, qSS1 with the 9311 alleles promoting seed storability was further validated in near-isogenic line and its derived-F2 population. The other locus (qSS3.1) for seed storability colocalized with a locus for germination ability under hydrogen peroxide, which is recognized as an oxidant molecule that causes lipid damage. Transgenic experiments validated that a candidate gene (OsFAH2) resides the qSS3.1 region controlling seed storability and antioxidant capability. Overexpression of OsFAH2 that encodes a fatty acid hydroxylase reduced lipid preoxidation and increased seed storability. These findings provide new insights into the genetic and physiological bases of seed storability and will be useful for the improvement of seed storability in rice.

Advancements in the preparation of high-performance liquid chromatographic organic polymer monoliths for the separation of small-molecule drugs.

The various advantages of organic polymer monoliths, including relatively simple preparation processes, abundant monomer availability, and a wide application range of pH, have attracted the attention of chromatographers. Organic polymer monoliths prepared by traditional methods only have macropores and mesopores, and micropores of less than 50 nm are not commonly available. These typical monoliths are suitable for the separation of biological macromolecules such as proteins and nucleic acids, but their ability to separate small molecular compounds is poor. In recent years, researchers have successfully modified polymer monoliths to achieve uniform compact pore structures. In particular, microporous materials with pores of 50 nm or less that can provide a large enough surface area are the key to the separation of small molecules. In this review, preparation methods of polymer monoliths for high-performance liquid chromatography, including ultra-high cross-linking technology, post-surface modification, and the addition of nanomaterials, are discussed. Modified monolithic columns have been used successfully to separate small molecules with obvious improvements in column efficiency.

Antibiotic-loaded, silver core-embedded mesoporous silica nanovehicles as a synergistic antibacterial agent for the treatment of drug-resistant infections.

Drug-resistant bacterial infections have become one of the most serious risks in public health as they make the conventional antibiotics less efficient. There is an urgent need for developing new generations of antibacterial agents in this field. In this work, a nanoplatform of LEVO-loaded and silver core-embedded mesoporous silica nanovehicles (Ag@MSNs@LEVO) is demonstrated as a synergistic antibacterial agent for the treatment of drug-resistant infections both in vitro and in vivo. The combination of the inner Ag core and the loaded antibiotic drug in mesopores endows the single-particle nanoplatform with a synergistic effect on killing the drug-resistant bacteria. The nanoplatform of Ag@MSNs@LEVO exhibits superior antibacterial activity to LEVO-loaded MSNs (MSNs@LEVO) and silver core-embedded MSNs (Ag@MSNs) in vitro. In the in vivo acute peritonitis model, the infected drug-resistant Escherichia coli GN102 in peritoneal cavity of the mice is reduced by nearly three orders of magnitude and the aberrant pathological feature of spleen and peritoneum disappears after treatment with Ag@MSNs@LEVO. Importantly, this nanopaltform renders no obvious toxic side effect to the mice during the tested time. There is no doubt that this study strongly indicates a promising potential of Ag@MSNs@LEVO as a synergistic and safety therapy tool for the clinical drug-resistant infections.

Determination of pKa values of alendronate sodium in aqueous solution by piecewise linear regression based on acid-base potentiometric titration.

As a mono-sodium salt form of alendronic acid, alendronate sodium presents multi-level ionization for the dissociation of its four hydroxyl groups. The dissociation constants of alendronate sodium were determined in this work by studying the piecewise linear relationship between volume of titrant and pH value based on acid-base potentiometric titration reaction. The distribution curves of alendronate sodium were drawn according to the determined pKa values. There were 4 dissociation constants (pKa1=2.43, pKa2=7.55, pKa3=10.80, pKa4=11.99, respectively) of alendronate sodium, and 12 existing forms, of which 4 could be ignored, existing in different pH environments.

Comparative subproteome analysis of three representative Leptospira interrogans vaccine strains reveals cross-reactive antigens and novel virulence determinants.

Pathogenic Leptospira spp. causes leptospirosis in China and throughout the world. Here, we have sequenced two L. interrogans moderately virulent vaccine strains JDL03 (serovar Canicola) and JDL10 (serovar Hebdomadis) used in China. We selected a subproteomic approach to identify surface-exposed proteins including OMPs and extracellular proteins of these two strains plus a highly virulent vaccine strain 56601 (serovar Lai). Comparative surface-exposed proteome among the three strains indicated 81 cores, 61 dispensable and 122 unique surface-exposed proteins. Finally, the 10 highly conserved surface-exposed or subsurface proteins included two known cross-reactive antigens (LipL32 and LA_3469) and another two novel antigens (LA_0136 and LA_0505) displaying conserved immunoreactivity among 15 Chinese epidemic serovars. Furthermore, many potential virulence factors were detected in these identified surface-exposed proteins, such as Loa22, LipL32, LenC, LenF and OmpL37. Interestingly, LipL45, ClpA and ClpB, exhibiting obvious amino acid mutations among str.56601, str.JDL03 and JDL10, might contribute to virulence differences observed among these strains. Additionally, specific surface-exposed proteins in virulent str.56601 were considered to be key virulence determinants, such as Zn-dependent protease, cholesterol oxidase precursor, and so on. In all, we had relatively complete surface-exposed subproteomes of L. interrogans, which will enhance our understanding of leptospiral pathogenesis and key virulence determinants. BIOLOGICAL SIGNIFICANCE: The present work demonstrates the use of genomic sequencing and subproteomic studies for the identification of potential vaccine and diagnostic antigen candidates against leptospirosis. The data show the conserved surface-exposed proteins to be novel potentially vaccine/diagnostic candidates. Furthermore, the data also show that LipL45, ClpA, ClpB and a lipoprotein from these three strains plus another highly virulent strain Fiocruz L1-130 contain specific amino acid mutations in strains JDL03 and JDL10. The surface-exposed subproteome of pathogenic L. interrogans could provide valuable information to gain a more complete understanding of leptospiral pathogenesis and virulence determinants.