Search

SUMMARY: The ability of immature maize (Zea mays) embryos to form embryonic calluses (ECs) is highly genotype dependent, which limits transgenic breeding development in maize. Here, we report the association map‐based cloning of ZmSAUR15 using an association panel (AP) consisting of 309 inbred lines with diverse formation abilities for ECs. We demonstrated that ZmSAUR15, which encodes a small auxin‐upregulated RNA, acts as a negative effector in maize EC induction. Polymorphisms in the ZmSAUR15 promoter that influence the expression of ZmSAUR15 transcripts modulate the EC induction capacity in maize. ZmSAUR15 is involved in indole‐3‐acetic acid biosynthesis and cell division in immature embryo‐derived callus. The ability of immature embryos to induce EC formation can be improved by the knockout of ZmSAUR15, which consequently increases the callus regeneration efficiency. Our study provides new insights into overcoming the genotypic limitations associated with EC formation and improving genetic transformation in maize. Significance Statement: Embryonic callus formation is highly genotype dependent in maize, which largely limits maize transgenic breeding development. This study found that ZmSAUR15 negatively effects embryonic callus formation in maize. The polymorphisms in the ZmSAUR15 promoter influence its expression. Furthermore, ZmSAUR15 modulates indole‐3‐acetic acid biosynthesis and cell division in callus. [ABSTRACT FROM AUTHOR]

The free moisture in crop kernels after being naturally dried is referred to as kernel moisture content (KMC). Maize KMC reflects grain quality and influences transportation and storage of seeds. We used an IBM Syn10 DH maize population consisting of 249 lines and an association panel comprising 310 maize inbred lines to identify the genetic loci affecting maize KMC in three environments. Using the IBM population detected 13 QTL on seven chromosomes, which were clustered into nine common QTL. Genome‐wide association analysis (GWAS) identified 16 significant SNPs across the 3 environments, which were linked to 158 genes across the three environments. Combined QTL mapping and GWAS found two SNPs that were located in two of the mapped QTL, respectively. Twenty‐three genes were linked with the loci co‐localized in both populations. Of these 181 genes, five have previously been reported to be associated with KMC or to regulate seed development. These associations were verified by candidate gene association analysis. Two superior alleles and one favorable haplotype for Zm00001d007774 and Zm00001d047868 were found to influence KMC. These findings provide insights into molecular mechanisms underlying maize KMC and contribute to the use of marker‐assisted selection for breeding low‐KMC maize. [ABSTRACT FROM AUTHOR]

Ear tip‐barrenness (ETB) phenotype threatens crop yield, because it reduces the kernel number per ear. The genetic basis of ETB in maize remains largely unknown. Herein, a genome‐wide association study (GWAS) and quantitative trait loci (QTL) mapping were jointly applied to identify the significant genetic loci interrelated with ETB. Six significant SNPs were detected at a stringent P‐value threshold (1.95 × 10−6). Additionally, four environment‐stable SNPs were co‐detected across a single environment and best linear unbiased prediction (BLUP) model at a less stringent P‐value threshold (1 × 10−4). The above 10 SNPs were closely linked to 6 candidate genes, which mainly involved seed development, photosynthesis and ethylene response. Moreover, the ratio of superior allele at each significant SNP ranged from 0 to 83.33% in 30 investigated maize elite lines. QTL mapping identified 14 QTL with phenotypic variation explained (PVE) ranging from 3.64 to 7.09%, of which one QTL (qETB2‐1) was repeatedly identified in two environments. Combined analysis of GWAS and QTL mapping showed that one SNP (PZE‐102175229, chromosome 2: 217 66 Mb) was located in the QTL (qETB2‐2, chromosome 2: 215 90–217 82 Mb). Eighteen gene models situated in the linkage disequilibrium (LD) region of the co‐localized SNP were further used to evaluate their correlation with ETB by candidate gene association analysis. Two superior haplotypes and two superior alleles were detected among 74 lines for Zm00001d007195, Zm00001d007197 and Zm00001d007201. These results provide more information for clarifying the molecular mechanism of ETB and for speeding up the genetic improvement of maize varieties. [ABSTRACT FROM AUTHOR]

Summary: Kernel size‐related traits are the most direct traits correlating with grain yield. The genetic basis of three kernel traits of maize, kernel length (KL), kernel width (KW) and kernel thickness (KT), was investigated in an association panel and a biparental population. A total of 21 single nucleotide polymorphisms (SNPs) were detected to be most significantly (P < 2.25 × 10−6) associated with these three traits in the association panel under four environments. Furthermore, 50 quantitative trait loci (QTL) controlling these traits were detected in seven environments in the intermated B73 × Mo17 (IBM) Syn10 doubled haploid (DH) population, of which eight were repetitively identified in at least three environments. Combining the two mapping populations revealed that 56 SNPs (P < 1 × 10−3) fell within 18 of the QTL confidence intervals. According to the top significant SNPs, stable‐effect SNPs and the co‐localized SNPs by association analysis and linkage mapping, a total of 73 candidate genes were identified, regulating seed development. Additionally, seven miRNAs were found to situate within the linkage disequilibrium (LD) regions of the co‐localized SNPs, of which zma‐miR164e was demonstrated to cleave the mRNAs of Arabidopsis CUC1,CUC2 and NAC6 in vitro. Overexpression of zma‐miR164e resulted in the down‐regulation of these genes above and the failure of seed formation in Arabidopsis pods, with the increased branch number. These findings provide insights into the mechanism of seed development and the improvement of molecular marker‐assisted selection (MAS) for high‐yield breeding in maize. [ABSTRACT FROM AUTHOR]

The windings of a traction transformer are always be threatened by the fluctuation of the load. Frequency response analysis (FRA) is regarded as the most effective method to diagnose the winding deformation. Appropriate FRA modelling method may help to predict typical winding faults for large transformers. The existing model usually simplify dozens of winding disks into several disks, it is applicable when analysing small displacement. However, when the disks between windings are seriously misplaced, the conventional model may not be suitable. This study presents an improved lumped parameter circuit model considering intersection capacitances and mutual inductance between windings. The feasibility of the proposed model is verified based on a 10 kV test transformer. Finally, the model is applied for a 220 kV traction transformer, the variation of parameters and features are analysed for axial displacement of different windings. The results show that the axial displacement may lead to increase of resonance frequency and decrease of amplitude. The low‐frequency band (1–30 kHz) may be regarded as visible features for diagnosing axial displacement of H winding and the middle frequency band (50–200 kHz) may be a characteristic band for diagnosing axial displacement of T winding. [ABSTRACT FROM AUTHOR]

Auto‐transformer (AT) power traction networks with a parallel connection are the unique mode on high‐speed electric railways in China. The up line and down line of power traction networks are connected at substation (SS), AT post (ATP) and sectioning post (SP) through busbars, circuit breakers and disconnectors. Currently, when a fault occurs on power traction networks, the feeder line protection devices at the up line and down line in SS trip simultaneously. After that, the nonfault line and instantaneous fault line recover by means of autoreclosing. This tripping mode enlarges the power supply‐interrupted region. Based on the analysis of circuit networks of power traction networks on high‐speed electric railways, the interrelations of currents in SS and ATP and in SS and SP are derived. When a fault occurs on one side of the power traction networks, the feeder currents in ATP and SP flow from the nonfault side to the fault side. The relation between feeder currents in SS and ATP and between feeder currents in SS and SP reflect this characteristic. A criterion for discriminating the fault side and selective‐tripping scheme of breakers is proposed based on the correlation analysis of feeder current fault components in multisite. The simulation results show that this scheme can discriminate fault side and make a selective trip rapidly and correctly. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

SUMMARY: Inorganic phosphorus (Pi) is an essential element in numerous metabolic reactions and signaling pathways, but the molecular details of these pathways remain largely unknown. In this study, metabolite profiles of maize (Zea mays L.) leaves and roots were compared between six low‐Pi‐sensitive lines and six low‐Pi‐tolerant lines under Pi‐sufficient and Pi‐deficient conditions to identify pathways and genes associated with the low‐Pi stress response. Results showed that under Pi deprivation the concentrations of nucleic acids, organic acids and sugars were increased, but that the concentrations of phosphorylated metabolites, certain amino acids, lipid metabolites and nitrogenous compounds were decreased. The levels of secondary metabolites involved in plant immune reactions, including benzoxazinoids and flavonoids, were significantly different in plants grown under Pi‐deficient conditions. Among them, the 11 most stable metabolites showed significant differences under low‐ and normal‐Pi conditions based on the coefficient of variation (CV). Isoleucine and alanine were the most stable metabolites for the identification of Pi‐sensitive and Pi‐resistant maize inbred lines. With the significant correlation between morphological traits and metabolites, five low‐Pi‐responding consensus genes associated with morphological traits and simultaneously involved in metabolic pathways were mined by combining metabolites profiles and genome‐wide association study (GWAS). The consensus genes induced by Pi deficiency in maize seedlings were also validated by reverse‐transcription quantitative polymerase chain reaction (RT‐qPCR). Moreover, these genes were further validated in a recombinant inbred line (RIL) population, in which the glucose‐6‐phosphate‐1‐epimerase encoding gene mediated yield and correlated traits to phosphorus availability. Together, our results provide a framework for understanding the metabolic processes underlying Pi‐deficient responses and give multiple insights into improving the efficiency of Pi use in maize. Significance statement: Metabolite profiling and GWAS were applied to reveal maize low‐Pi response mechanisms. [ABSTRACT FROM AUTHOR]

Multi‐point grounding of the core is one of the common transformer faults. In this study, a homogenisation model based on the finite element method is developed for calculating multi‐point grounding current of the transformer core. The equivalent conductivity in the direction normal to the laminations is determined by the analysis of fault current distribution and calculation of anisotropic resistances of the iron core, especially, considering the influence of insulation coating on the silicon steel sheet. The validity of the proposed model is verified by comparing the three‐dimensional finite element simulation results with the experimental results. Finally, two typical faults are simulated to further study the characteristics of multi‐point grounding current based on a distribution transformer, which may be useful for the optimisation of transformer core design. [ABSTRACT FROM AUTHOR]

Voltage distortions are characterized by the harmonic spectrum of the nonlinear load (NLL) and harmonic impedance of the whole system. On one hand, the harmonic impedance is at the peak value when the frequency is at the resonance point, which leads to serious voltage distortions. On the other hand, harmonic distortions will be excited from excessive harmonic emission without resonance. In order to address the above causes, shifting the resonance frequency sensitivity (RFS) and the critical individual harmonic voltage distortion (IHDV) sensitivity (IHDS) indices are presented here to control the critical IHDV and total harmonic voltage distortion (THDV). The main idea is to find and adjust the most sensitive network parameter against these sensitivity indices until the harmonic distortion reaches the required value. A three-bus test system and the IEEE 14-bus system are used to verify the proposed method. Comparison of the results shows that these indices complement each other for solving the harmonics problems with or without harmonic resonance. The sensitivity-based methods can be effective for system optimization and filter design by considering harmonic resonance. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

To develop genetic markers associated with tolerance to low phosphorus, we identified candidate phosphate starvation responsive ( PSR) genes and developed their intron length polymorphism ( ILP) markers in maize on a genome-wide scale. Based on the known plant PSR genes, 161 candidate PSR genes were identified. Of these genes, 138 genes contained at least one intron and were then used to develop 606 PSR- ILP markers by designing PCR primers to the intron-flanking exonic regions. PCR evaluation was performed on 43 randomly selected PSR- ILP markers in 30 maize inbred lines. Of the primers, 88.4% amplified stable and pure products in all maize inbred lines, and 53.5% of the markers showed ILP, with PIC values ranging from 0.06 to 0.80. The result of clustering analysis of the 30 maize inbred lines, based on the polymorphism of 23 ILP markers, suggests that the ILP markers developed in this study are not only efficient for genetic diversity analysis but also potentially useful for marker assisted selection for tolerance to low phosphorus. [ABSTRACT FROM AUTHOR]