Two complementary genes in a presence-absence variation contribute to indica-japonica reproductive isolation in rice.

Understanding the evolutionary forces in speciation is a central goal in evolutionary biology. Asian cultivated rice has two subspecies, indica and japonica, but the underlying mechanism of the partial reproductive isolation between them remains obscure. Here we show a presence-absence variation (PAV) at the Se locus functions as an indica-japonica reproductive barrier by causing hybrid sterility (HS) in indica-japonica crosses. The locus comprises two adjacent genes: ORF3 encodes a sporophytic pollen killer, whereas ORF4 protects pollen in a gametophytic manner. In F1 of indica-japonica crosses, pollen with the japonica haplotype, which lacks the sequence containing the protective ORF4, is aborted due to the pollen-killing effect of ORF3 from indica. Evolutionary analysis suggests ORF3 is a gene associated with the Asian cultivated rice species complex, and the PAV has contributed to the reproductive isolation between the two subspecies of Asian cultivated rice. Our analyses provide perspectives on rice inter-subspecies post-zygotic isolation, and will promote efforts to overcome reproductive barriers in indica-japonica hybrid rice breeding.

Genetic dissection of grain iron concentration in hexaploid wheat (Triticum aestivum L.) using a genome-wide association analysis method.

Iron (Fe) is an essential micronutrient of the body. Low concentrations of bioavailable Fe in staple food result in micronutrient malnutrition. Wheat (Triticum aestivum L.) is the most important global food crop and thus has become an important source of iron for people. Breeding nutritious wheat with high grain-Fe content has become an effective means of alleviating malnutrition. Understanding the genetic basis of micronutrient concentration in wheat grains may provide useful information for breeding for high Fe varieties through marker-assisted selection (MAS). Hence, in the present study, genome-wide association studies (GWAS) were conducted for grain Fe. An association panel of 207 accessions was genotyped using a 660K SNP array and phenotyped for grain Fe content at three locations. The genotypic and phenotypic data obtained thus were used for GWAS. A total of 911 SNPs were significantly associated with grain Fe concentrations. These SNPs were distributed on all 21 wheat chromosomes, and each SNP explained 5.79-25.31% of the phenotypic variations. Notably, the two significant SNPs (AX-108912427 and AX-94729264) not only have a more significant effect on grain Fe concentration but also have the reliability under the different environments. Furthermore, candidate genes potentially associated with grain Fe concentration were predicted, and 10 candidate genes were identified. These candidate genes were related to transport, translocation, remobilization, and accumulationof ironin wheat plants. These findings will not only help in better understanding the molecular basis of Fe accumulation in grains, but also provide elite wheat germplasms to develop Fe-rich wheat varieties through breeding.

In-depth genetic analysis reveals conditioning of polyphenol oxidase activity in wheat grains by cis regulation of TaPPO2A-1 expression level.

Time-dependent darkening and discoloration of wheat product caused by high polyphenol oxidase enzymes (PPO) activity is the most undesirable character in wheat processing industry. We performed GWAS of PPO activity in wheat grains utilizing an association panel and identified 22 significant SNPs. The most significant GWAS peak on chromosome 2A was verified by QTL analysis of PPO activity. The candidate gene for this GWAS peak was identified as TaPPO2A-1, which was the highest expressed PPO gene in wheat grains. The expression level of TaPPO2A-1 was significantly correlated with PPO activity. The most significant association signal for GWAS of the expression values of TaPPO2A-1 pinpointed to the genomic region containing TaPPO2A-1. The results suggested that cis regulation of TaPPO2A-1 expression is the key factor in regulation of PPO activity in wheat grains. The conclusion was further enhanced by haplotype analysis of seven SNPs in the promoter of TaPPO2A-1.

Identification of Novel Genomic Regions and Superior Alleles Associated with Zn Accumulation in Wheat Using a Genome-Wide Association Analysis Method.

Micronutrient deficiencies, and especially zinc (Zn) deficiency, pose serious health problems to people who mainly depend on cereal-based diets. Here, we performed a genome-wide association study (GWAS) to detect the genetic basis of the Zn accumulation in wheat (Triticum aestivum L.) grains with a diversity panel of 207 bread wheat varieties. To uncover authentic quantitative trait loci (QTL) controlling Zn accumulation, the varieties were planted in three locations. In total, 29 unique loci associated with Zn grain accumulation were identified. Notably, seven non-redundant loci located on chromosomes 1B, 3B, 3D, 4A, 5A, 5B, and 7A, were detected at least in two environments. Of these quantitative trait loci (QTL), six coincided with known QTL or genes, whereas the highest effect QTL on chromosome 3D identified in this study was not reported previously. Searches of public databases revealed that the seven identified QTL coincided with seven putative candidate genes linked to Zn accumulation. Among these seven genes, NAC domain-containing protein gene (TraesCS3D02G078500) linked with the most significant single nucleotide polymorphism (SNP) AX-94729264 on chromosome 3D was relevant to metal accumulation in wheat grains. Results of this study provide new insights into the genetic architecture of Zn accumulation in wheat grains.

Genetic Basis of Gluten Aggregation Properties in Wheat (Triticum aestivum L.) Dissected by QTL Mapping of GlutoPeak Parameters.

Bread wheat is one of the most important crops worldwide, supplying approximately one-fifth of the daily protein and the calories for human consumption. Gluten aggregation properties play important roles in determining the processing quality of wheat (Triticum aestivum L.) products. Nevertheless, the genetic basis of gluten aggregation properties has not been reported so far. In this study, a recombinant inbred line (RIL) population derived from the cross between Luozhen No. 1 and Zhengyumai 9987 was used to identify quantitative trait loci (QTL) underlying gluten aggregation properties with GlutoPeak parameters. A linkage map was constructed based on 8,518 SNPs genotyped by specific length amplified fragment sequencing (SLAF-seq). A total of 33 additive QTLs on 14 chromosomes were detected by genome-wide composite interval mapping (GCIM), four of which accounted for more than 10% of the phenotypic variation across three environments. Two major QTL clusters were identified on chromosomes 1DS and 1DL. A premature termination of codon (PTC) mutation in the candidate gene (TraesCS1D02G009900) of the QTL cluster on 1DS was detected between Luozhen No. 1 and Zhengyumai 9987, which might be responsible for the difference in gluten aggregation properties between the two varieties. Subsequently, two KASP markers were designed based on SNPs in stringent linkage with the two major QTL clusters. Results of this study provide new insights into the genetic architecture of gluten aggregation properties in wheat, which are helpful for future improvement of the processing quality in wheat breeding.

Fabrication of core@shell structural Fe-Fe2O3@PHCP nanochains with high saturation magnetization and abundant amino groups for hexavalent chromium adsorption and reduction.

The rational design of novel adsorption materials is imperative to remove toxic metal species from the polluted water. Herein, a core@shell structural Fe-Fe2O3@poly (hexachlorocyclotriphosphazene-co-polyethylenimine) (Fe-Fe2O3@PHCP) magnetic nanochain with high saturation magnetization was fabricated and used for effective adsorption and reduction of hexavalent chromium. The morphology and microstructure of Fe-Fe2O3@PHCP were characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The effects of concentration, pH, contact time, temperature and coexisting ions on Cr (VI) removal were studied. Four kinetic models (pseudo-first-order, pseudo-second-order, Bangham and intraparticle diffusion models) and two isotherm models (Freundlich and Langmuir) were used to fit experimental data. Results show the adsorption capacity of Fe-Fe2O3@PHCP for Cr (VI) is up to 229.0 mg g-1. The excellent performance was ascribed to the favorable reduction of Cr (VI) to Cr (III), followed by the chelation of Cr (III) with imino groups. Meanwhile, the residual Cr (VI) were adsorbed on protonated amino and imino groups. The adsorption process is exothermic and spontaneous and nicely follows pseudo-second-order kinetics, intraparticle diffusion model and Langmuir isotherm model. These results indicated that easily separable Fe-Fe2O3@PHCP magnetic nanochains could be a promising adsorbent to remediate chromate wastewater.

Magnetic hollow poly(cyclotriphosphazene-co-4,4'-sulfonyldiphenol)-Fe3O4 hybrid nanocapsules for adsorbing Safranine T and catalytic oxidation of 3,3',5,5'-tetramethylbenzidine.

The development of novel adsorbents with high adsorption capacity and easy recovery property is imperative in the field of wastewater treatment. In this study, a hard template-induced assembly strategy was developed to fabricate the magnetic hollow poly(cyclotriphosphazene-co-4,4'-sulfonyldiphenol)-Fe3O4 (PZS-Fe3O4) hybrid nanocapsules, in which Fe3O4 nanoparticles were well embedded in the cross-linked PZS shell. The resulting samples were well characterized using SEM, TEM, EDS, FT-IR, VSM, XPS, XRD and N2 sorption. Then, using Safranine T (ST) as model dye, the adsorption behavior of as-prepared hollow PZS-Fe3O4 nanocapsules including adsorption kinetics, adsorption isotherms, adsorption mechanism, and recyclability were systematically evaluated and discussed. The results revealed that the magnetic hollow PZS-Fe3O4 nanocapsules own high adsorption capacity towards ST dye and outstanding magnetic separation functionality. The pseudo-second-order kinetic model and the Langmuir model can well describe the experimental data, and the adsorption process is controlled by more than one diffusion step. The interaction between ST dye and hollow PZS-Fe3O4 nanocapsules is ascribed to π-π interaction and electrostatic interaction. The thermodynamic parameters demonstrated that the adsorption processes were physical, endothermic, and spontaneous. Additionally, the magnetic hollow PZS-Fe3O4 nanocapsules also shows excellent peroxidase-like catalytic activity in the oxidation of 3,3',5,5'-tetramethylbenzidine with H2O2, indirectly confirming the adsorption kinetic results.

Large-scale fabrication of N-doped porous carbon nanosheets for dye adsorption and supercapacitor applications.

The development of novel large-scale synthesis protocols for heteroatom-doped porous carbon nanosheets is highly imperative for wastewater purification and high-performance electrode materials. In the present work, we propose a simple and feasible explosion-assisted activation strategy to fabricate a kind of N-doped porous carbon nanosheet (N-PCNS) at a large scale, in which only lactose and zinc nitrate were used as raw materials. The obtained N-PCNS possesses hierarchical micro- and mesopore nanostructures with a high specific surface area of 879 m2 g-1 while keeping a high nitrogen content of 3.73 at%. The adsorption properties of the N-PCNS were systematically evaluated through adsorption of neutral red (NR) dye. The adsorption capacity of the N-PCNS was as high as 439.6 mg g-1, meanwhile the adsorption process exhibited fine correlation with the Langmuir isotherm and pseudo-second-order kinetic models. As an electrode material for supercapacitors, the specific capacitance of the N-PCNS is up to 263 F g-1 at 1 A g-1 and 194 F g-1 at 20 A g-1, revealing superior rate performance. The capacitance retention after 10 000 cycles at 20 A g-1 is 96%, demonstrating excellent cycling stability. Our work provides an effective approach to achieve the large-scale preparation of high-performance doped carbon materials.

Highly-efficient and selective adsorption of anionic dyes onto hollow polymer microcapsules having a high surface-density of amino groups: Isotherms, kinetics, thermodynamics and mechanism.

Organic dye pollution in the water environment is a problem of global concern. Adsorption is demonstrated as a promising technology to remove organic dyes from wastewater, in which the development of highly-efficient adsorbents is still the challenging task. Herein, we reported the facile fabrication of polyamine-based cyclophosphazene hybrid (PCP-NH2) hollow microcapsules with cross-linked structure, generated by one-step precipitation polymerization between hexachlorocyclotriphosphazene and branched polyethyleneimine, and subsequent acetone treatment. Their morphology, composition and structure were confirmed by SEM, TEM, FTIR, TGA, and XPS. The endowment of hollow PCP-NH2 microcapsules as potential adsorbents were thoroughly evaluated using eight organic dyes with different surface charges. The adsorption action of hollow PCP-NH2 microcapsules highly depends on the surfaces charges, exhibiting highly-efficient and selective adsorption behavior towards anionic dyes. Especially, The adsorption capacity of the hollow PCP-NH2 microcapsules towards anionic dyes of EY, ACBK, MO and EB reaches up to 1196.36, 1190.65, 1142.77 and 1040.92 mg/g at 25 °C, respectively. The adsorption kinetics shows a better fit to pseudo second-order kinetic model, compared to pseudo-first-order kinetic and Weber's intraparticle diffusion models. The adsorption equilibrium data followed the Langmuir isotherm well. The adsorption thermodynamic experiments demonstrated that adsorption was a physisorption process with endothermic and spontaneous characteristic.

Characterization of epistatic interaction of QTLs LH8 and EH3 controlling heading date in rice.

Heading date is a critical trait for adaptation of rice to different cultivation areas and cropping seasons. We evaluated the heading dates of 1,123 chromosome segments substitution lines (CSSLs) in the genetic background of an elite rice variety Huajingxian74 (HJX74). A CSSL with the substituted segments from Zihui100 exhibited late heading under both natural long-day (NLD) and natural short-day (NSD) conditions, and the late heading phenotype was controlled by two novel epistatic loci on chromosome 8 and chromosome 3, respectively, termed LH8 and EH3. The function of EH3 was dependent on the LH8 genotype through epistatic interaction between EH3(Zihui100) and LH8(Zihui100) alleles. Genetic and molecular characterization revealed LH8 encodes a CCAAT-box-binding transcription factor with Heading date1 (Hd1)-binding activity and may delay flowering by repressing the expression of Early heading date1 (Ehd1). Our work provides a solid foundation for further study on gene interaction in heading date and has application in breeding rice with greater adaptability.