RESUMO
Rice (Oryza sativa) is a leading source of dietary cadmium (Cd), a non-essential heavy metal that poses a serious threat to human health. There are significant variations in grain-Cd levels in natural rice populations, which make the breeding of low-Cd rice a cost-effective way to mitigate grain-Cd accumulation. However, the genetic factors that regulate grain-Cd accumulation have yet to be fully established, thereby hindering the development of low-Cd varieties. Here, we reported a low-Cd quantitative trait locus, CF1, that has the potential to reduce Cd accumulation in rice grains. CF1 is allelic to the metal transporter OsYSL2, which transports Fe from the roots to the shoots. However, it is incapable of binding Cd, and thus, reduces grain-Cd levels indirectly rather than directly in the form of upward delivery. Further analysis showed that high expression levels of CF1 improve Fe nutrition in the shoots, subsequently inhibiting Cd uptake by systemically inhibiting expression of the main Cd uptake gene OsNramp5 in the roots. Compared with the CF1 allele from '02428' (CF102428 ), higher expression levels of CF1 from 'TQ' (CF1TQ ) increased the Fe contents and decreased Cd levels in rice grains. In natural rice populations, CF1TQ was found to be a minor allele, while CF102428 is present in most japonica rice, suggesting that CF1TQ could be widely integrated into the japonica rice genome to generate low-Cd varieties. Overall, these results broaden our mechanistic understanding of the natural variation in grain-Cd accumulation, supporting marker-assisted selection of low-Cd rice.
Assuntos
Cádmio , Oryza , Cádmio/metabolismo , Grão Comestível/metabolismo , Oryza/metabolismo , Melhoramento Vegetal , Raízes de PlantasRESUMO
RATIONALE: The amino acid-nitrogen (AA-N) isotope analysis of naturally abundant or isotope-labeled samples is indispensable for tracing nitrogen transfer in soil nitrogen biogeochemical cycling processes. Despite the usefulness of AA-N isotope analysis, the preparation methods are complex and time-consuming, and necessitate the use of toxic reagents. METHODS: We present an improved, rapid method for AA-N isotope analysis with high precision. At a high pH, AA-N was released and oxidized to N2 O using ClO- under vacuum. Additionally, purge-and-trap isotope ratio mass spectrometry was used to analyze N2 O. Moreover, we investigated the effect of various factors on the N2 O conversion process with glycine and applied the results to seven representative single-N AAs (alanine, serine, cysteine, aspartic acid, glutamic acid, leucine, and phenylalanine) and five poly-N AAs (lysine, arginine, histidine, tryptophan, and asparagine), as well as side-chain analogs, blank reagent, and other N forms. RESULTS: The concentration of ClO- and the pH were determined to be crucial factors for achieving desirable AA-N to N2 O conversion efficiencies. Glycine-N had the highest N2 O yield of 70%, with isotopic results consistent with those of the reference values at a high precision (within 0.5 for natural abundance and 0.01 atom% for 15 N-enrichment) at the nanomolar N level. Additionally, the α-NH2 AAs were labile, and the single-N AAs were more easily converted to N2 O than poly-N AAs. With the exception of γ-aminobutyric acid, the N2 O conversion efficiencies of the side-chain N analogs were very low (below 5%). This method was also applicable to the 15 N analysis of the total free AAs in complex soil samples without interference from analytical blanks and other forms of N. CONCLUSIONS: Our method is highly selective for the α-NH2 groups of an amino acid, and the oxidation of the side chain is difficult. In addition, the method is sensitive, rapid, and convenient, and does not require toxic reagents.
Assuntos
Nitrogênio , Solo , Alanina , Aminoácidos/química , Arginina , Asparagina , Ácido Aspártico , Cisteína , Ácido Glutâmico , Glicina , Histidina , Leucina , Lisina , Nitrogênio/análise , Isótopos de Nitrogênio/análise , Fenilalanina , Serina , Triptofano , Ácido gama-AminobutíricoRESUMO
The elements Zinc (Zn) and cadmium (Cd) have similar chemical and physical properties, but contrasting physiological effects in higher organisms. In plants, Zn/Cd transport is mediated by various transporter proteins belonging to different families. In this study, we functionally characterized two Zn transporter genes in rice (Oryza sativa), ZINC TRANSPORTER5 (OsZIP5) and ZINC TRANSPORTER9 (OsZIP9), which are tandem duplicates and act synergistically in Zn/Cd uptake. Both genes encode plasma membrane-localized proteins with influx transporter activity. The expression profiles of OsZIP5 and OsZIP9 overlap in the root epidermis and respond to the local Zn status in the root. However, OsZIP9 is also regulated by systemic signals of Zn status from the shoot. OsZIP5 functions redundantly to OsZIP9, but has a relatively weaker effect. Plants with the knockout mutations oszip5, oszip9, or oszip5oszip9 show impaired Zn/Cd uptake. The decreased Zn/Cd levels and growth retardation in the oszip5 mutant are less severe than in the oszip9 mutant. However, the double mutant oszip5oszip9 showed an enhanced Zn deficiency phenotype compared with the single mutants, and few double-knockout plants were able to survive the entire growth cycle without excessive Zn supply. Transgenic plants overexpressing OsZIP9 had markedly enhanced Zn/Cd levels in the aboveground tissues and brown rice. The results of our study fill a gap in current knowledge of Zn uptake and improve our understanding of Zn/Cd accumulation in rice.
Assuntos
Cádmio/metabolismo , Oryza/metabolismo , Proteínas de Plantas/metabolismo , Zinco/metabolismo , Sequência de Aminoácidos , Sequência de Bases , Transporte Biológico , Proteínas de Transporte de Cátions/química , Proteínas de Transporte de Cátions/genética , Proteínas de Transporte de Cátions/metabolismo , Duplicação Gênica , Perfilação da Expressão Gênica , Regulação da Expressão Gênica de Plantas , Genes de Plantas , Mutação/genética , Especificidade de Órgãos/genética , Oryza/genética , Filogenia , Proteínas de Plantas/química , Proteínas de Plantas/genética , Raízes de Plantas/genética , Plantas Geneticamente Modificadas , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Sementes/metabolismo , Transdução de SinaisRESUMO
KEY MESSAGE: Genome differentiation has shaped the divergence in element concentration between rice subspecies and contributed to the correlation among trace minerals in the rice grain. The balance between trace minerals in rice, a staple food for more than half of the world's population, is crucial for human health. However, the genetic basis underlying the correlation between trace minerals has not been fully elucidated. To address this issue, we first quantified the concentrations of 11 trace minerals in the grains of a diversity panel of 575 rice cultivars. We found that eight elements were accumulated at significantly different levels between the indica and japonica subspecies, and we also observed significant correlation patterns among a number of elements. Further, using a genome-wide association study, we identified a total of 96 significant association loci (SALs). The differentiation of the major-effect SALs along with the different number of high-concentration alleles present in the two subspecies shaped the different element performance in indica and japonica varieties. Only a few SALs located in clusters and the majority of SALs showed subspecies/subgroup differentiation, indicating that the correlations between elements in the diversity panel were mainly caused by genome differentiation instead of shared genetic basis. The genetic architecture unveiled in this study will facilitate improvement in breeding for trace mineral content.
Assuntos
Grão Comestível/genética , Oryza/genética , Oligoelementos/análise , Alelos , Grão Comestível/química , Grão Comestível/metabolismo , Estudo de Associação Genômica Ampla , Genótipo , Metagenômica , Família Multigênica , Oryza/química , Oryza/metabolismo , Fenótipo , Filogenia , Melhoramento Vegetal , Locos de Características Quantitativas , Sequenciamento Completo do GenomaRESUMO
Rice has lower zinc (Zn) but higher cadmium (Cd) content in grains than other staple crops. Understanding the molecular mechanisms involved in Zn and Cd transportation could benefit homeostatic control, facilitating optimisation of Zn and Cd levels to provide maximum nutrition and safety. In this study, we functionally characterised in planta the rice (Oryza sativa) transporter OsZIP7, which encodes a plasma membrane-localised protein with influx transport activity for both Zn and Cd. OsZIP7 was expressed in parenchyma cells of vascular bundles in roots and nodes. OsZIP7 knockout resulted in retention of Zn and Cd in roots and basal nodes, which hindered their upward delivery to upper nodes and brown rice. And a short-term labelling experiment with the stable 67Zn isotope showed that Zn was distributed toward roots and basal regions and away from leaves in the mutant compared with wild-type rice. Thus, OsZIP7 plays an integral role in xylem loading in roots and inter-vascular transfer in nodes to preferentially deliver Zn and Cd to developing tissues and rice grains.
Assuntos
Cádmio/metabolismo , Proteínas de Transporte de Cátions/metabolismo , Oryza/metabolismo , Proteínas de Plantas/metabolismo , Zinco/metabolismo , Proteínas de Transporte de Cátions/genética , Regulação da Expressão Gênica de Plantas , Técnicas de Inativação de Genes , Genes de Plantas , Hidroponia , Modelos Biológicos , Oryza/genética , Oryza/crescimento & desenvolvimento , Proteínas de Plantas/genética , Raízes de Plantas/metabolismo , Feixe Vascular de Plantas/metabolismo , Plantas Geneticamente Modificadas , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Xilema/metabolismoRESUMO
RATIONALE: Soil microbial heterotrophic C-CO2 respiration is important for C cycling. Soil CO2 differentiation and quantification are vital for understanding soil C cycling and CO2 emission mitigation. Presently, soil microbial respiration (SR) quantification models are based on native soil organic matter (SOM) and require consistent monitoring of δ13C and CO2. METHODS: We present a new apparatus for achieving in situ soil static chamber incubation and simultaneous CO2 and δ13C monitoring by cavity ring-down spectroscopy (CRDS) coupled with a soil culture and gas introduction module (SCGIM) with multi-channel. After a meticulous five-point inter-calibration, the repeatability of CO2 and δ13C values by using CRDS-SCGIM were determined, and compared with those obtained using gas chromatography (GC) and isotope ratio mass spectrometry (IRMS), respectively. We examined the method regarding quantifying SR with various concentrations and enrichment of glucose and then applied it to investigate the responses of SR to the addition of different exogenous organic materials (glucose and rice residues) into paddy soils during a 21-day incubation. RESULTS: The CRDS-SCGIM CO2 and δ13C measurements were conducted with high precision (< 1.0 µmol/mol and 1, respectively). The optimal sampling interval and the amount added were not exceeded 4 h and 200 mg C/100 g dry soil in a 1 L incubation bottle, respectively; the 13C-enrichment of 3%-7% was appropriate. The total SR rates observed were 0.6-4.2 µL/h/g and the exogenous organic materials induced -49%-28% of priming effects in native SOM mineralisation. CONCLUSIONS: Our results show that CRDS-SCGIM is a method suitable for the quantification of soil microbial CO2 respiration, requiring less extensive lab resources than GC/IRMS.
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Background: Gonadotrophin-releasing hormone (GnRH) administration significantly decreases the pregnancy rate of recipient ewes after embryo transfer, possibly because GnRH affects endometrial epithelial cell function. Therefore, this study investigated the effect of GnRH on endometrial epithelial cells. Methods: Transcriptome sequencing was used to determine the regulatory effect of GnRH on the ewe endometrium, and the S100A4 gene, which showed altered transcription, was screened as a candidate regulator of this effect. Endometrial epithelial cells were further isolated, the S100A4 protein was immunoprecipitated, and host proteins that interacted with S100A4 were identified by mass spectrometry. We further verified the effects of S100A4 and GNAI2 on the proliferation of endometrial epithelial cells via overexpression/knockdown experiments and subsequent CCK-8 and EdU assays. The effect of S100A4 deletion in endometrial cells on reproduction was verified in mice with S100A4 knockout. Results: Our results showed that S100A4 gene transcription in endometrial cells was significantly inhibited after GnRH administration. GNAI2 was identified as a downstream interacting protein of S100A4, and S100A4 was confirmed to activate the MAPK signaling pathway to promote cell proliferation by targeting GNAI2. Conclusion: GnRH can suppress the expression of S100A4 in the endometrium, consequently inhibiting the proliferation of endometrial cells through the S100A4/GNAI2/MAPK signaling pathway. These findings suggest a potential explanation for the limited efficacy of GnRH in promoting embryo implantation.
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Rice (Oryza sativa L.) is a major staple food that provides not only dietary calories but also trace elements for the global inhabitants. The insufficiency of mineral nutrients and the potential accumulation of excessive toxic elements in grains pose risks to human health. The substantial natural variations in mineral accumulation in rice grains presents potentials for genetic improvements of rice via biofortifications of essential mineral nutrients and eliminations of toxic elements in grains. However, the genetic mechanisms underlying the natural variations in mineral accumulation have not been fully explored to date owing to unstable phenotypic variations, which are attributed to poor genetic performance and strong environmental effects. In this study, we first compared the genetic performance of different normalization approaches in determining the grain-Cd, grain-Mn, and grain-Zn variations in rice in different genetic populations. Then through quantitative trait loci (QTLs) identification in two rice inter-ectype populations, three QTLs, including qCd7, qMn3, and qZn7, were identified and the QTLs were found to exhibit allelic differentiation in the different ecotypes. Our results were expected to broaden our understanding for mineral accumulation in rice and propose the potential functional alleles that can be explored for further genetic improvement of rice.
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China is the cradle of Chinese herb medicines,with rich plant resources. However, traditional processing methods have many disadvantages, such as high comsumption of organic solvent, long extraction time and high loss of effective constituents. For the purpose of rational use of Chinese herb medicines and accurate analysis on their constituents,the sample pre-treatment method with magnetic nanoparticles as the carrier brought new opportunities in recent years. after consulting literatures,the essay summarizes traditional extraction methods of Chinese herb medicines, characteristics of magnetic materials and their application in the analysis on Chinese herb medicines.
Assuntos
Medicamentos de Ervas Chinesas/análise , Magnetismo/métodos , Plantas Medicinais/química , Medicamentos de Ervas Chinesas/isolamento & purificação , Medicina Tradicional ChinesaRESUMO
Rice (Oryza sativa L.), a staple for half of the world's population, usually accumulates high levels of cadmium (Cd) in the grain when planted in the Cd-contaminated paddy fields. Genetic improvements using natural variation of grain-Cd accumulation is the most cost-effective way to mitigate the risk of excess Cd accumulation. However, as a complex trait, grain-Cd accumulation is susceptible to environmental variation, which challenges to characterize the genetic nature and subsequently the stable performance of grain-Cd accumulation. To boost the genetic effect on grain-Cd performance, we established an approach of normalization using the comparative grain-Cd value (CCd) following a contrasting field design. Identification of the genetic locus responsible for CCd variation help us develop a low-grain-Cd variety de novo, named 'Lushansimiao', which had lower grain-Cd levels in a large-scale field test and can produce Cd-safe rice following prolonged irrigations in the field with intermediate levels of Cd pollution. Combined CCd evaluating and low-Cd allelic genotyping, another six varieties were also identified as low-grain-Cd rice. Our study paves the way to efficiently quantify the genetic nature of grain-Cd accumulation in rice, and the stable low-Cd rice varieties will help to mitigate the risk of excess Cd accumulation in rice.
Assuntos
Oryza , Poluentes do Solo , Cádmio/análise , Grão Comestível/química , Genótipo , Oryza/genética , Solo , Poluentes do Solo/análiseRESUMO
The effects of dietary rebaudioside A inclusion on feed intake, digestion of nutrients, rumen fermentation, and blood biochemical parameters of goats were evaluated in a replicated 3 × 3 Latin square study. Nine adult goats during summer were fed a basal forage/concentrate-based diet and the forage was chopped rice straw. The three dietary treatments were 0, 350, and 700 mg rebaudioside A per kg chopped rice straw on a DM basis. No significant improvement was observed in dry matter intake (DMI) of forage and diet among treatments. Nutrient digestibility of DM and organic matter (OM) showed a significant trend (p < .10) across groups. Rebaudioside A inclusion significantly (p < .01) increased the concentration of total volatile fatty acids in the rumen, however, there were no differences in concentration of ruminal ammonia, and molar proportions of acetate, propionate, and butyrate. About blood metabolites, increasing rebaudioside A in the diet caused a quadratic response in glucose and total protein, and albumin concentrations. Under the conditions of this study, supplementation with rebaudioside A at 350 and 700 mg/kg forage did not improve consumption of rice straw-based diet in adult goats in summer. However, the responses in digestibility, rumen fermentation, and blood metabolites appear to indicate the potential of rebaudioside A as a bio-active substance in goats.
Assuntos
Dieta/veterinária , Suplementos Nutricionais , Digestão/efeitos dos fármacos , Diterpenos do Tipo Caurano/administração & dosagem , Diterpenos do Tipo Caurano/farmacologia , Ingestão de Alimentos/efeitos dos fármacos , Fermentação/efeitos dos fármacos , Cabras/metabolismo , Cabras/fisiologia , Nutrientes/metabolismo , Rúmen/metabolismo , Edulcorantes/farmacologia , Ração Animal , Animais , Análise Química do Sangue , Ácidos Graxos Voláteis/metabolismo , Glucose/metabolismo , Cabras/sangue , Temperatura Alta , Masculino , Proteínas/metabolismo , Estações do Ano , Albumina SéricaRESUMO
Rice, a staple crop for nearly half the planet's population, tends to absorb and accumulate excessive cadmium (Cd) when grown in Cd-contaminated fields. Low levels of Cd can degrade the quality of rice grains, while high levels can inhibit the growth of rice plants. There is genotypic diversity in Cd distribution and Cd tolerance in different rice varieties, but their underlying genetic mechanisms are far from elucidated, which hinders genetic improvements. In this study, a joint study of phenotypic investigation with quantitative trait loci (QTLs) analyses of genetic patterns of Cd distribution and Cd tolerance was performed using a biparent population derived from japonica and indica rice varieties. We identified multiple QTLs for each trait and revealed that additive effects from various loci drive the inheritance of Cd distribution, while epistatic effects between various loci contribute to differences in Cd tolerance. One pleiotropic locus, qCddis8, was found to affect the Cd distribution from both roots to shoots and from leaf sheaths to leaf blades. The results expand our understanding of the diversity of genetic control over Cd distribution and Cd tolerance in rice. The findings provide information on potential QTLs for genetic improvement of Cd distribution in rice varieties.
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The ionome of the rice grain is crucial for the health of populations that consume rice as a staple food. However, the contribution of phenotypic plasticity to the variation of rice grain ionome and the genetic architecture of phenotypic plasticity are poorly understood. In this study, we investigated the rice grain ionome of a rice diversity panel in up to eight environments. A considerable proportion of phenotypic variance can be attributed to phenotypic plasticity. Then, phenotypic plasticity and mean phenotype were quantified using Bayesian Finlay-Wilkinson regression, and a significant correlation between them was observed. However, the genetic architecture of mean phenotype was distinct from that of phenotypic plasticity. Also, the correlation between them was mainly attributed to the phenotypic divergence between rice subspecies. Furthermore, the results of whole-genome regression analysis showed that the genetic loci related to phenotypic plasticity can explain a considerable proportion of the phenotypic variance in some environments, especially for Cd, Cu, Mn, and Zn. Our study not only sheds light on the genetic architecture of phenotypic plasticity of the rice grain ionome but also suggests that the genetic loci which related to phenotypic plasticity are valuable in rice grain ionome improvement breeding.
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The objective of this study was to evaluate the effects of dietary inclusion of tevioside on feed intake, feeding behavior, nutrient digestion, rumen fermentation, and serum biochemical parameters in goats. Nine male Xiangdong black goats (21.8 ± 1.5 kg of body weight) were used in a replicated 3 × 3 Latin square. All goats were fed a basal diet including concentrate and forage (chopped rice traw). The three treatments were 0, 400, or 800 mg stevioside per kg chopped rice traw on a dry matter (DM) basis. Dry matter intake of forage and total diet linearly increased (p = 0.03 and p = 0.04) with increasing stevioside in the diet. There was no effect (p > 0.05) of stevioside inclusion in the diets on eating time, rumination time, or total mastication time for the goats. Total volatile fatty acid (VFA) concentration in the rumen responded quadratically (p < 0.01), decreasing from 0 to 400 mg/kg stevioside inclusion and increasing thereafter. The inclusion of steviosid in the diets promoted a quadratic increase in the apparent total tract digestibilities of neutral detergent fiber (NDF) (p = 0.02) and acid detergent fiber (ADF) (p = 0.01). Based on the results of this experiment, it could be concluded that supplementing goat diets with stevioside at 400 mg/kg to 800 mg/kg forage (about 270 to 541 mg/kg diet) resulted in increased dry intake of forage and total diet, suggesting that stevioside has positive potential as a feed additive to improve feed intake.
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The enzyme activity, which is closely related to soil material cycling (mineralization, transformation, etc.), can reflect soil quality and nutrient status. In order to explore the effect of long-term fertilization on the enzyme activity in paddy soil profile (0-40 cm), soils with organic fertilizer and inorganic fertilizer, and non-fertilized soils were selected, and the carbon and nitrogen contents, and the activities of ß-1,4-glucosidase (BG), and ß-1,4-N-acetylglucosaminidase (NAG) in 10cm depths of soil were analyzed. The results showed that the activities of BG and NAG in the soils treated with inorganic fertilizer and organic fertilizer increased by 0.73-47.87 nmol·(g·h)-1 and 1.33-128.81 nmol·(g·h)-1, and 0.19-9.72 nmol·(g·h)-1 and 0.92-57.66 nmol·(g·h)-1, respectively, compared to those for non-fertilized soil. Soil enzyme activity decreased with increasing soil depth. Soil enzyme activity in soil from 0-20 cm was significantly higher than that of soil from 20-40 cm. Soil enzyme activities were significantly affected by long term fertilization at different soil depths. RDA analysis showed that soil carbon and nitrogen contents had significant positive relationships with the activities of BG and NAG in the 0-20 cm soil profiles, however, negative relationships were observed in the 20-40 cm soil profiles. The long-term application of organic fertilizer significantly increased soil biomass and enzyme activity, both of which decreased with the increase in soil depth. Long-term fertilization could increase soil nutrient contents, microbial biomass, and extracellular enzyme activities, which has important theoretical significance for optimizing farmland fertilizer management and improving soil productivity.
Assuntos
Enzimas/análise , Fertilizantes , Microbiologia do Solo , Carbono , N-Acetilglucosaminiltransferases/análise , Nitrogênio , Oryza , Fósforo , Solo , beta-Glucosidase/análiseRESUMO
Photosynthesized carbon (C) is an important source of soil organic C in paddy fields, and its input and distribution are affected by rice growth and soil fertility. Fertilizer application plays an important role in rice growth. The 13C pulse-labeling method was used to quantify the dynamics and distribution of input photosynthesized C in the rice-(rhizosphere-and bulk-) soil system and its response to nitrogen fertilizer (N) application. The results suggested that N fertilization significantly increased the rice aboveground and the root biomass and decreased the rice biomass root/shoot ratio. The amount of assimilated 13C gradually decreased in the rice plants but gradually decreased over 0-6 days and increased over 6-26 days in the rhizosphere and bulk soil during rice growth. N fertilization significantly increased the amount of assimilated 13C in the rhizosphere soil by 9.5%-32.6% compared with the control. In comparison to the unfertilized treatment, the application of N fertilization resulted in higher photosynthetic13C in rice aboveground and in the root by 24.5%-134.7% and 9.1%-106%, respectively. With the N fertilized and unfertilized treatments, 85.5%-93.2% and 91.3%-95.7%, respectively, of input photosynthetic 13C was distributed in the rice plants. The results suggested that N fertilization significantly affected the distribution of photosynthesized C in the rice-soil system (P<0.01). After 26 days of pulse labeling, the distribution of photosynthetic 13C into rice aboveground was increased by 13.4%, while the distribution into the rhizosphere and bulk soil were decreased by 21.9% and 52.2%, respectively, in the N fertilized treatments compared with the unfertilized treatments. Therefore, the N application increased the distribution of photosynthesized carbon in the soil-rice system but decreased the accumulation in the rhizosphere and bulk soil. The findings of this study provided a theoretical basis for our understanding of the dynamic of photosynthetic C in the plant-soil system and the assimilation of the soil organic matter pool in the paddy soil ecosystem.
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Carbono/química , Fertilizantes , Nitrogênio/química , Oryza/crescimento & desenvolvimento , Solo/química , RizosferaRESUMO
To get a better understanding of the microbial autotrophic carbon sequestration potential of paddy fields and its mechanisms, soil incubation experiment was conducted for four representative paddy soils. The molecular biological methods[quantitative PCR (qPCR), clone library and terminal-restriction fragment length polymorphism (T-RFLP) technique] based on cbbL and cbbM genes encoding the key enzymes[ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO)] of Calvin cycle were used to determine the abundance and diversity of autotrophic microbes. The results showed that, after 45 days of incubation, carbon dioxide fixation autotrophic microbial abundances were generally increased compared with those before incubation, and cbbL gene abundances were approximately three magnitudes higher than those of cbbM. Dominant microbial populations varied among the four paddy soils, and most of these OTUs were distantly related to known sequences, only part of them could be grouped into Proteobacteria and Actinobacteria. RDA analysis results showed that soil organic carbon (SOC), cation exchange capacity (CEC), pH, clay, silk and sand content had significant effects on the CO2 fixation microbial community. Consequently, the results of this study provide significant reference to understand the role of microorganisms in carbon cycle process. The results are helpful for providing a scientific basis for scientific management of paddy soil fertility and low carbon agriculture construction.
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Bactérias/classificação , Dióxido de Carbono/química , Filogenia , Microbiologia do Solo , Carbono , Oryza , Fotossíntese/genética , Polimorfismo de Fragmento de Restrição , Ribulose-Bifosfato Carboxilase/genética , SoloRESUMO
Ecological enzyme activities are closely relevant to the carbon and nitrogen decomposition and mineralization of paddy soils, which can reflect the growth and metabolism of microorganisms. In order to clarify the response to nitrogen application by different enzymes in the rhizosphere and bulk soil of rice, the rhizosphere and bulk soil were identified using a rhizosphere bag. In addition, the ß-1,4-glucosidase (BG) enzyme; ß-1,4-N-acetylglucosaminidase (NAG) enzyme; and the effects of the rhizosphere, nitrogen application, and growth period on soil enzyme activities were analyzed. The results showed that the activity of the BG enzyme decreased by 7.4-13.5 nmol·(g·h)-1 in the jointing stage and increased by 7.0-31.4 nmol·(g·h)-1 in the maturity stage, and the activity of the BG enzyme in the rhizosphere and bulk soil also changed with the growth period of rice.compared with no nitrogen fertilizer, nitrogen application increased NAG enzyme activity by 1.1 times and rhizosphere soil by 0.3 times in the bulk soil in the maturity stage. Nitrogen application and growth period had significant effects on soil BG enzyme activity, whereas the interaction within rice growth stage, nitrogen application, and rhizosphere effect had significant effects on NAG enzyme activity. The result of RDA showed that the soil microbial biomass carbon (MBC) and dissolved organic carbon (DOC) contents mainly affected the activity of extracellular enzymes in the rice rhizosphere soil, whereas the activities of enzymes in the rhizosphere soil were mainly affected by microbial biomass nitrogen (MBN) and NH4+-N. The relationships between soil enzyme activity and various factors are complex, and the effects of nitrogen addition on microbial community composition needs to be considered after accounting for plant physiological characteristics, soil enzyme activity, and soil characteristics.
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N-Acetilglucosaminiltransferases/metabolismo , Nitrogênio/química , Oryza/crescimento & desenvolvimento , Rizosfera , Microbiologia do Solo , Solo/química , beta-Glucosidase/metabolismo , CarbonoRESUMO
A suitable fractionation method of phosphorus (P) is a key to effective assessment of soil P componential features. Here a new biologically-based P (BBP) method was used to evaluate the P fractions in the upland and paddy soils across large-scale area in China. The soil P was divided into four components:â soluble or rhizosphere-intercepted (CaCl2-P), â¡ organic acid activated and inorganic weakly bound (Citrate-P), ⢠enzyme mineralization of organic P (Enzyme-P), ⣠potential activation of inorganic P (HCl-P). Then, the relationships between biologically-based P fractions and standard Olsen-P were investigated, and driving factors of P fractions were identified. The results showed that P content was in order of HCl-P>Citrate-P>Enzyme-P>CaCl2-P. All P components of upland soil displayed higher levels than those of paddy soil. Moreover, the P components were highly positively correlated with the Olsen-P, suggesting that each P component contributed to soil P availability. However, it was found that Olsen-P was most highly correlated with CaCl2-P and Enzyme-P (R2=0.359; R2=0.386) in upland soil, while Olsen-P was most highly with Citrate-P (R2=0.788) in paddy soil. This result indicated that available P of upland soil was mainly from organic P mineralization and soluble P, and available P in paddy soil was mainly from inorganic P activation. Redundancy analysis (RDA) showed that the P components were mainly affected by soil pH and silt content, which suggested that it could enhance the P availability via regulating soil pH in the agricultural activities.
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Fósforo/química , Solo/química , Agricultura , China , Fazendas , Fertilizantes , OryzaRESUMO
Cadmium (Cd) is a toxic element, and rice is known to be a leading source of dietary Cd for people who consume rice as their main caloric resource. Hybrid rice has dominated rice production in southern China and has been adopted worldwide. The characteristics of high yield heterosis of rice hybrids makes the public think intuitively that the hybrid rice accumulates more Cd in grain than do inbred cultivars. A detailed understanding of the genetic basis of grain Cd accumulation in hybrids and developing Cd-safe rice are one of the top priorities for hybrid rice breeders at present. In this study, we investigated genetic diversity and grain Cd levels in 617 elite rice hybrids collected from the middle and lower Yangtze River Valley in China and 68 inbred cultivars from around the world. We found that there are large variations in grain Cd accumulation in both the hybrids and their inbred counterparts. However, we found grain Cd levels in the rice hybrids to be similar to the levels in indica rice inbreds, suggesting that the hybrids do not accumulate more Cd than do the inbred rice cultivars. Further analysis revealed that the high heritability of Cd accumulation in the grain and the single indica population structure increases the risk of Cd over-accumulation in hybrid rice. The genetic effects of Cd-related QTLs, which have been identified in related Cd-QTL mapping studies, were also determined in the hybrid rice population. Four QTLs were identified as being associated with the variation in grain Cd levels; three of these loci exhibited obvious indica-japonica differentiations. Our study will provide a better understanding of grain Cd accumulations in hybrid rice, and pave the way toward effective breeding for high-yielding, low grain-Cd hybrids in the future.