Grains from cereals contribute an important source of protein to human food, and grain protein content (GPC) is an important determinant of nutritional quality in cereals. Here we show that the quantitative trait locus (QTL) qPC1 in rice controls GPC by regulating the synthesis and accumulation of glutelins, prolamins, globulins, albumins and starch. qPC1 encodes a putative amino acid transporter OsAAP6, which functions as a positive regulator of GPC in rice, such that higher expression of OsAAP6 is correlated with higher GPC. OsAAP6 greatly enhances root absorption of a range of amino acids and has effects on the distribution of various amino acids. Two common variations in the potential cis-regulatory elements of the OsAAP6 5′-untranslated region seem to be associated with GPC diversity mainly in indica cultivars. Our results represent the first step toward unravelling the mechanism of regulation underlying natural variation of GPC in rice.
High-performance catalysts are extremely required for controlling NO emission via selective catalytic reduction (SCR), and to acquire a common structural feature of catalytic sites is one key prerequisite for developing such catalysts. We design a single-atom catalyst system and achieve a generic characteristic of highly active SCR catalytic sites. A single-atom Mo1/Fe2O3 catalyst is developed by anchoring single acidic Mo ions on (001) surfaces of reducible α-Fe2O3, and the individual Mo ion and one neighboring Fe ion are thus constructed as one dinuclear site. As the number of the dinuclear sites increases, SCR rates increase linearly but the apparent activation energy remains almost unchanged, evidencing the identity of the dinuclear active sites. We further design W1/Fe2O3 and Fe1/WO3 and find that tuning acid or/and redox properties of dinuclear sites can alter SCR rates. Therefore, this work provides a design strategy for developing improved SCR catalysts via optimizing acid-redox properties of dinuclear sites.
Grain size is a major determinant of grain yield and quality in rice (Oryza sativa), and was therefore an important selective target during domestication and breeding (Fitzgerald et al., 2009) (Takano- Kai et al., 2009). In the past few decades, a dozen grain size-related QTLs/genes have been cloned (Huang et al., 2013;Zuo and Li, 2014). Pyramiding grain size QTLs to breed high-yielding and high-quality rice varieties has proved to be a great success. For example, by pyramiding the nonfunctional alleles gs3 and gw8 in line HJX74, Wang et al. (2012) converted a line with short and wide grains into one with slender grains and substantially improved grain quality. By pyramiding the GW7 allele from TFA and gs3, Wang et al. (2015) developed new high-yielding indica hybrid rice varieties with simultaneously improved yield and grain quality. Thus, it is of considerable importance to identify more grain size QTLs to facilitate further improvement in rice yield and quality.
The development of catalysts with simultaneous resistance to alkalis and sulfur poisoning is of great importance for efficiently controlling NOx emissions using the selective catalytic reduction of NOx with NH3 (SCR), because the conventional V2O5/WO3-TiO2 catalysts often suffer severe deactivation by alkalis. Here, we support V2O5 on a hexagonal WO3 (HWO) to develop a V2O5/HWO catalyst, which has exceptional resistance to alkali and sulfur poisoning in the SCR reactions. A 350 μmol g(-1) K(+) loading and the presence of 1,300 mg m(-3) SO2 do not almost influence the SCR activity of the V2O5/HWO catalyst, and under the same conditions, the conventional V2O5/WO3-TiO2 catalysts completely lost the SCR activity within 4 h. The strong resistance to alkali and sulfur poisoning of the V2O5/HWO catalysts mainly originates from the hexagonal structure of the HWO. The HWO allows the V2O5 to be highly dispersed on the external surfaces for catalyzing the SCR reactions and has the relatively smooth surfaces and the size-suitable tunnels specifically for alkalis' diffusion and trapping. This work provides a useful strategy to develop SCR catalysts with exceptional resistance to alkali and sulfur poisoning for controlling NOx emissions from the stationary source and the mobile source.
Stigma exsertion, a key determinant of the rice mating system, greatly contributes to the application of heterosis in rice. Although a few quantitative trait loci associated with stigma exsertion have been fine mapped or cloned, the underlying genetic architecture remains unclear. We performed a genome-wide association study on stigma exsertion and related floral traits using 6.5 million SNPs characterized in 533 diverse accessions of Oryza sativa. We identified 23 genomic loci that are significantly associated with stigma exsertion and related traits, three of which are co-localized with three major grain size genes GS3, GW5, and GW2. Further analyses indicated that these three genes affected the stigma exsertion by controlling the size and shape of the spikelet and stigma. Combinations of GS3 and GW5 largely defined the levels of stigma exsertion and related traits. Selections of these two genes resulted in specific distributions of floral traits among subpopulations of O. sativa. The low stigma exsertion combination gw5GS3 existed in half of the cultivated rice varieties; therefore, introducing the GW5gs3 combination into male sterile lines is of high potential for improving the seed production of hybrid rice.
CeO-based catalysts have attracted widespread attention in environmental-protection applications, including selective catalytic reduction (SCR) of NO by NH, and their catalytic performance is often intimately associated with the supports used. However, the issue of how to choose the supports of such catalysts still remains unresolved. Herein, we systematically study the support effect in SCR over CeO-based catalysts by using three representative supports, AlO, TiO, and hexagonal WO (HWO), with different acidic and redox properties. HWO, with both acidic and reducible properties, achieves an optimal support effect; that is, CeO/HWO exhibits higher catalytic activity than CeO supported on acidic AlO or reducible TiO. Transmission electron microscopy and X-ray diffraction techniques demonstrate that acidic supports (HWO and AlO) are favorable for the dispersion of CeO on their surfaces. X-ray photoelectron spectroscopy coupled with theoretical calculations reveals that reducible supports (HWO and TiO) facilitate strong electronic CeO-support interactions. Hence, the excellent catalytic performance of CeO/HWO is mainly ascribed to the high dispersion of CeO and the optimal electronic CeO-support interactions. This work shows that abundant Brønsted acid sites and excellent redox ability of supports are two critical requirements for the design of efficient CeO-based catalysts.
The development of efficient alkali-based catalysts for the abatement of formaldehyde (HCHO), a ubiquitous air pollutant, is economically desirable. Here we comparatively study the catalytic performance of two single-atom catalysts, Na/HMO and Ag/HMO (HMO = Hollandite manganese oxide), in the complete oxidation of HCHO at low temperatures, in which the products are only CO and HO. These catalysts are synthesized by anchoring single sodium ions or silver atoms on HMO(001) surfaces. Synchrotron X-ray diffraction patterns with structural refinement together with transmission electron microscopy images demonstrate that single sodium ions on the HMO(001) surfaces of Na/HMO have the same local structures as silver atoms of Ag/HMO. Catalytic tests reveal that Na/HMO has higher catalytic activity in low-temperature oxidation of HCHO than Ag/HMO. X-ray photoelectron spectra and soft X-ray absorption spectra show that the surface lattice oxygen of Na/HMO has a higher electronic density than that of Ag/HMO, which is responsible for its higher catalytic efficiency in the oxidation of HCHO. This work could assist the rational design of cheap alkali metal catalysts for controlling the emissions of volatile organic compounds such as HCHO.
Maghemite (γ-Fe 2 O 3 ) with a spinel structure, consisting of tetrahedral Fe 3+ (Fe 3+ Td ) and octahedral Fe 3+ (Fe 3+ Oh ) sites, has been intensively investigated as an environmentally benign catalyst for selective catalytic reduction (SCR) of NO x with NH 3 . In most cases, Fe 3+ Oh sites were regarded as catalytically active sites (CASs). Here we identify the CASs in SCR by substituting Fe 3+ Oh or Fe 3+ Td sites of γ-Fe 2 O 3 with catalytically inactive Ti 4+ or Zn 2+ , respectively. The SCR activity of γ-Fe 2 O 3 is preserved after Ti 4+ doping but drastically decreases when the catalyst is doped with Zn 2+ , demonstrating that Fe 3+ Td sites serve as CASs in SCR. Synchrotron X-ray absorption spectra coupled with density functional theory calculations reveal that the transfer of an electron from inactive Fe 2+ to active Fe 3+ in the tetrahedral site is easier than that in the octahedral site, making the tetrahedral iron sites active in SCR.
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