Conserved defense responses between maize and sorghum to Exserohilum turcicum.

BACKGROUND:Exserohilum turcicum is an important pathogen of both sorghum and maize, causing sorghum leaf blight and northern corn leaf blight. Because the same pathogen can infect and cause major losses for two of the most important grain crops, it is an ideal pathosystem to study plant-pathogen evolution and investigate shared resistance mechanisms between the two plant species. To identify sorghum genes involved in the E. turcicum response, we conducted a genome-wide association study (GWAS). RESULTS:Using the sorghum conversion panel evaluated across three environments, we identified a total of 216 significant markers. Based on physical linkage with the significant markers, we detected a total of 113 unique candidate genes, some with known roles in plant defense. Also, we compared maize genes known to play a role in resistance to E. turcicum with the association mapping results and found evidence of genes conferring resistance in both crops, providing evidence of shared resistance between maize and sorghum. CONCLUSIONS:Using a genetics approach, we identified shared genetic regions conferring resistance to E. turcicum in both maize and sorghum. We identified several promising candidate genes for resistance to leaf blight in sorghum, including genes related to R-gene mediated resistance. We present significant advancements in the understanding of host resistance to E. turcicum, which is crucial to reduce losses due to this important pathogen

Inhibition of ethylene involved in resistance to E. turcicum in an exotic-derived double haploid maize population

Northern corn leaf blight (NCLB) is an economically important disease of maize. While the genetic architecture of NCLB has been well characterized, the pathogen is known to overcome currently deployed resistance genes, and the role of hormones in resistance to NCLB is an area of active research. The objectives of the study were (i) to identify significant markers associated with resistance to NCLB, (ii) to identify metabolic pathways associated with NCLB resistance, and (iii) to examine role of ethylene in resistance to NCLB. We screened 252 lines from the exotic-derived double haploid BGEM maize population for resistance to NCLB in both field and greenhouse environments. We used a genome wide association study (GWAS) and stepwise regression to identify four markers associated with resistance, followed by a pathway association study tool (PAST) to identify important metabolic pathways associated with disease severity and incubation period. The ethylene synthesis pathway was significant for disease severity and incubation period. We conducted a greenhouse assay in which we inhibited ethylene to examine the role of ethylene in resistance to NCLB. We observed a significant increase in incubation period and a significant decrease in disease severity between plants treated with the ethylene inhibitor and mock-treated plants. Our study confirms the potential of the BGEM population as a source of novel alleles for resistance. We also confirm the role of ethylene in resistance to NCLB and contribute to the growing body of literature on ethylene and disease resistance in monocots

Sodium channel endocytosis drives axon initial segment plasticity

Activity-dependent plasticity of the axon initial segment (AIS) endows neurons with the ability to adapt action potential output to changes in network activity. Action potential initiation at the AIS highly depends on the clustering of voltage-gated sodium channels, but the molecular mechanisms regulating their plasticity remain largely unknown. Here, we developed genetic tools to label endogenous sodium channels and their scaffolding protein, to reveal their nanoscale organization and longitudinally image AIS plasticity in hippocampal neurons in slices and primary cultures. We find that N-methyl-d-aspartate receptor activation causes both long-term synaptic depression and rapid internalization of AIS sodium channels within minutes. The clathrin-mediated endocytosis of sodium channels at the distal AIS increases the threshold for action potential generation. These data reveal a fundamental mechanism for rapid activity-dependent AIS reorganization and suggests that plasticity of intrinsic excitability shares conserved features with synaptic plasticity

WEST full tungsten operation with an ITER grade divertor

The mission of WEST (tungsten-W Environment in Steady-state Tokamak) is to explore long pulse operation in a full tungsten (W) environment for preparing next-step fusion devices (ITER and DEMO) with a focus on testing the ITER actively cooled W divertor in tokamak conditions. Following the successful completion of phase 1 (2016-2021), phase 2 started in December 2022 with the lower divertor made entirely of actively cooled ITER-grade tungsten mono-blocks. A boronization prior the first plasma attempt allowed for a smooth startup with the new divertor. Despite the reduced operating window due to tungsten, rapid progress has been made in long pulse operation, resulting in discharges with a pulse length of 100 s and an injected energy of around 300 MJ per discharge. Plasma startup studies were carried out with equatorial boron nitride limiters to compare them with tungsten limiters, while Ion Cyclotron Resonance Heating assisted startup was attempted. High fluence operation in attached regime, which was the main thrust of the first campaigns, already showed the progressive build up of deposits and appearance of dust, impacting the plasma operation as the plasma fluence increased. In total, the cumulated injected energy during the first campaigns reached 43 GJ and the cumulated plasma time exceeded 5 h. Demonstration of controlled X-Point Radiator regime is also reported, opening a promising route for investigating plasma exhaust and plasma-wall interaction issues in more detached regime. This paper summarises the lessons learned from the manufacturing and the first operation of the ITER-grade divertor, describing the progress achieved in optimising operation in a full W environment with a focus on long pulse operation and plasma wall interaction

Insights Into Disease Resistance: Genetic Architecture, Genes, And Pleiotropy In Maize

The genes and mechanisms underlying quantitative disease resistance remain largely elusive. The objective of this dissertation was to resolve the structure of multiple disease resistance loci, explore the dynamics that shape the genome at those loci, and identify genes associated with plant defense. In order to do this, both locus-specific and genome-wide approaches were taken, as each resistance locus has a unique resistance profile and mechanism(s) of resistance. Bins 1.02 and 1.06 of the maize genome carry loci of interest conditioning multiple disease resistance. The two loci differ in allelic diversity, pathogen specificity, and mechanism of resistance. The locus in bin 1.06 is particularly interesting, as it has been characterized as yield-stabilizing and exhibits signs of genome plasticity. I have used fine-mapping, association mapping, expression evidence, and mutant analysis to dissect these loci, identify candidate genes, and demonstrate the role of candidate genes in plant defense. Each locus was unique, although common themes arose. Both loci may have multiple underlying genes, demonstrating that the genetic architecture of disease resistance is complex. Resistance to multiple diseases appears to be due to linkage, although there may be a role for pleiotropy at both loci. Fine-mapping narrowed the intervals, and was complemented by association mapping and expression analysis to evaluate candidate genes. A putative remorin was implicated by fine-mapping and expression analysis; roughsheath2-interacting KH domain protein (rik) and pangloss1 (pan1) were identified through fine-mapping and association mapping. rik was later eliminated as a candidate for the QTL of interest through fine-mapping and association mapping. Mutants were used to confirm the role of candidate genes in plant defense, including for pan1 and the putative remorin. Based on these results, pan1 was inferred to be a susceptibility gene for NLB and Stewart's wilt, and increased resistance was correlated with decreased expression. Susceptibility conditioned by wild-type pan1 could be due to a passive mechanism, such as altered anatomical structures, or an active process, such as actin re-organization during pathogen attack. To test genome-wide association mapping candidate genes, mutants were identified and evaluated for NLB phenotype. Approximately 37% of the 123 families tested differed in disease phenotype from the background line. One of these was the putative remorin gene, which was inferred to contribute to resistance. Overall, I have examined candidate genes, explored genomic structure at these loci, and demonstrated a role for pan1 in resistance to multiple diseases

Chinese traders in Singapore: business practices and organizational dynamics

Jamann W. Chinese traders in Singapore: business practices and organizational dynamics. Bielefelder Studien zur Entwicklungssoziologie ; 60. Saarbrücken: Verl. für Entwicklungspolitik Breitenbach; 1994