A Kinesin-14 Motor Activates Neocentromeres to Promote Meiotic Drive in Maize.

Maize abnormal chromosome 10 (Ab10) encodes a classic example of true meiotic drive that converts heterochromatic regions called knobs into motile neocentromeres that are preferentially transmitted to egg cells. Here, we identify a cluster of eight genes on Ab10, called the Kinesin driver (Kindr) complex, that are required for both neocentromere motility and preferential transmission. Two meiotic drive mutants that lack neocentromere activity proved to be kindr epimutants with increased DNA methylation across the entire gene cluster. RNAi of Kindr induced a third epimutant and corresponding loss of meiotic drive. Kinesin gliding assays and immunolocalization revealed that KINDR is a functional minus-end-directed kinesin that localizes specifically to knobs containing 180 bp repeats. Sequence comparisons suggest that Kindr diverged from a Kinesin-14A ancestor ∼12 mya and has driven the accumulation of > 500 Mb of knob repeats and affected the segregation of thousands of genes linked to knobs on all 10 chromosomes.

On the Road to Breeding 4.0: Unraveling the Good, the Bad, and the Boring of Crop Quantitative Genomics.

Understanding the quantitative genetics of crops has been and will continue to be central to maintaining and improving global food security. We outline four stages that plant breeding either has already achieved or will probably soon achieve. Top-of-the-line breeding programs are currently in Breeding 3.0, where inexpensive, genome-wide data coupled with powerful algorithms allow us to start breeding on predicted instead of measured phenotypes. We focus on three major questions that must be answered to move from current Breeding 3.0 practices to Breeding 4.0: ( a) How do we adapt crops to better fit agricultural environments? ( b) What is the nature of the diversity upon which breeding can act? ( c) How do we deal with deleterious variants? Answering these questions and then translating them to actual gains for farmers will be a significant part of achieving global food security in the twenty-first century.

Eleven biosynthetic genes explain the majority of natural variation in carotenoid levels in maize grain.

Vitamin A deficiency remains prevalent in parts of Asia, Latin America, and sub-Saharan Africa where maize (Zea mays) is a food staple. Extensive natural variation exists for carotenoids in maize grain. Here, to understand its genetic basis, we conducted a joint linkage and genome-wide association study of the US maize nested association mapping panel. Eleven of the 44 detected quantitative trait loci (QTL) were resolved to individual genes. Six of these were correlated expression and effect QTL (ceeQTL), showing strong correlations between RNA-seq expression abundances and QTL allelic effect estimates across six stages of grain development. These six ceeQTL also had the largest percentage of phenotypic variance explained, and in major part comprised the three to five loci capturing the bulk of genetic variation for each trait. Most of these ceeQTL had strongly correlated QTL allelic effect estimates across multiple traits. These findings provide an in-depth genome-level understanding of the genetic and molecular control of carotenoids in plants. In addition, these findings provide a roadmap to accelerate breeding for provitamin A and other priority carotenoid traits in maize grain that should be readily extendable to other cereals.

Genetic mapping and prediction for novel lesion mimic in maize demonstrates quantitative effects from genetic background, environment and epistasis.

KEY MESSAGE: A novel locus was discovered on chromosome 7 associated with a lesion mimic in maize; this lesion mimic had a quantitative and heritable phenotype and was predicted better via subset genomic markers than whole genome markers across diverse environments. Lesion mimics are a phenotype of leaf micro-spotting in maize (Zea mays L.), which can be early signs of biotic or abiotic stresses. Dissecting its inheritance is helpful to understand how these loci behave across different genetic backgrounds. Here, 538 maize recombinant inbred lines (RILs) segregating for a novel lesion mimic were quantitatively phenotyped in Georgia, Texas, and Wisconsin. These RILs were derived from three bi-parental crosses using a tropical pollinator (Tx773) as the common parent crossed with three inbreds (LH195, LH82, and PB80). While this lesion mimic was heritable across three environments based on phenotypic ([Formula: see text] = 0.68) and genomic ([Formula: see text] = 0.91) data, transgressive segregation was observed. A genome-wide association study identified a single novel locus on chromosome 7 (at 70.6 Mb) also covered by a quantitative trait locus interval (69.3-71.0 Mb), explaining 11-15% of the variation, depending on the environment. One candidate gene identified in this region, Zm00001eb308070, is related to the abscisic acid pathway involving in cell death. Genomic predictions were applied to genome-wide markers (39,611 markers) contrasted with a marker subset (51 markers). Population structure explained more variation than environment in genomic prediction, but other substantial genetic background effects were additionally detected. Subset markers explained substantially less genetic variation (24.9%) for the lesion mimic than whole genome markers (55.4%) in the model, yet predicted the lesion mimic better (0.56-0.66 vs. 0.26-0.29). These results indicate this lesion mimic phenotype was less affected by environment than by epistasis and genetic background effects, which explain its transgressive segregation.

Genome-wide association mapping of resistance to the sorghum aphid in Sorghum bicolor.

Since 2013, the sorghum aphid (SA), Melanaphis sorghi (Theobald), has been a serious pest that hampers all types of sorghum production in the U.S. Known sorghum aphid resistance in sorghum is limited to a few genetic regions on SBI-06. In this study, a subset of the Sorghum Association Panel (SAP) was used along with some additional lines to identify genomic regions that confer sorghum aphid resistance. SAP lines were grown in the field and visually evaluated for SA resistance during the growing seasons of 2019 and 2020 in Tifton, GA. In 2020, the SAP accessions were also evaluated for SA resistance in the field using drone-based high throughput phenotyping (HTP). Flowering time was recorded in the field to confirm that our methods were sufficient for identifying known quantitative trait loci (QTL). This study combined phenotypic data from field-based visual ratings and reflectance data to identify genome-wide associated (GWAS) marker-trait associations (MTA) using genotyping-by-sequencing (GBS) data. Several MTAs were identified for SA-related traits across the genome, with a few common markers that were consistently identified on SBI-08 and SBI-10 for aphid count and plant damage, as well as loci for reflectance-based traits on SBI-02, SBI-03, and SBI-05. Candidate genes encoding leucine-rich repeats (LRR), Avr proteins, lipoxygenases (LOXs), calmodulins (CAM) dependent protein kinase, WRKY transcription factors, flavonoid biosynthesis genes, and 12-oxo-phytodienoic acid reductase were identified near SNPs that had significant associations with different SA traits. In this study, flowering time-related genes were also identified as a positive control for the methods. The total phenotypic variation explained by significant SNPs across SA-scored traits, reflectance data, and flowering time ranged from 6 to 61%, while the heritability value ranged from 4 to 69%. This study identified three new sources of resistant lines to sorghum aphid. These results supported the existing literature, and also revealed several new loci. Markers identified in this study will support marker-assisted breeding for sorghum aphid resistance.

Assessing the feasibility, acceptability and accessibility of a peer-delivered intervention to reduce harm and improve the well-being of people who experience homelessness with problem substance use: the SHARPS study.

BACKGROUND: For people experiencing homelessness and problem substance use, access to appropriate services can be challenging. There is evidence that the development of trusting relationships with non-judgemental staff can facilitate service engagement. Peer-delivered approaches show particular promise, but the evidence base is still developing. METHODS: The study used mixed methods to assess the feasibility, acceptability and accessibility of a peer-delivered, relational intervention to reduce harms and improve health/well-being, quality of life and social functioning, for people experiencing homelessness and problem substance use. Four Peer Navigators were employed to support individuals (n = 68 total, intervention participants). They were based in outreach services and hostels in Scotland and England. Qualitative interviews were conducted with intervention participants, Peer Navigators and staff in services, and observations were conducted in all settings. Quantitative outcomes relating to participants' substance use, physical and mental health, and quality of the Peer Navigator relationship, were measured via a 'holistic health check' with six questionnaires completed at two time-points. RESULTS: The intervention was found to be acceptable to, and feasible and accessible for, participants, Peer Navigators, and service staff. Participants reported improvements to service engagement, and feeling more equipped to access services independently. The lived experience of the Peer Navigators was highlighted as particularly helpful, enabling trusting, authentic, and meaningful relationships to be developed. Some challenges were experienced in relation to the 'fit' of the intervention within some settings. Among participants there were reductions in drug use and risky injecting practices. There were increases in the number of participants receiving opioid substitution therapy. Overall, the intervention was positively received, with collective recognition that the intervention was unique and highly valuable. While most of the measures chosen for the holistic health check were found to be suitable for this population, they should be streamlined to avoid duplication and participant burden. CONCLUSIONS: The study established that a peer-delivered, relational harm reduction intervention is acceptable to, and feasible and accessible for, people experiencing homelessness and problem substance use. While the study was not outcomes-focused, participants did experience a range of positive outcomes. A full randomised controlled trial is now required to assess intervention effectiveness. TRIAL REGISTRATION: Study registered with ISRCTN: 15900054.

Large-scale replicated field study of maize rhizosphere identifies heritable microbes.

Soil microbes that colonize plant roots and are responsive to differences in plant genotype remain to be ascertained for agronomically important crops. From a very large-scale longitudinal field study of 27 maize inbred lines planted in three fields, with partial replication 5 y later, we identify root-associated microbiota exhibiting reproducible associations with plant genotype. Analysis of 4,866 samples identified 143 operational taxonomic units (OTUs) whose variation in relative abundances across the samples was significantly regulated by plant genotype, and included five of seven core OTUs present in all samples. Plant genetic effects were significant amid the large effects of plant age on the rhizosphere microbiome, regardless of the specific community of each field, and despite microbiome responses to climate events. Seasonal patterns showed that the plant root microbiome is locally seeded, changes with plant growth, and responds to weather events. However, against this background of variation, specific taxa responded to differences in host genotype. If shown to have beneficial functions, microbes may be considered candidate traits for selective breeding.

Maize YABBY Genes drooping leaf1 and drooping leaf2 Regulate Plant Architecture.

Leaf architecture directly influences canopy structure, consequentially affecting yield. We discovered a maize (Zea mays) mutant with aberrant leaf architecture, which we named drooping leaf1 (drl1). Pleiotropic mutations in drl1 affect leaf length and width, leaf angle, and internode length and diameter. These phenotypes are enhanced by natural variation at the drl2 enhancer locus, including reduced expression of the drl2-Mo17 allele in the Mo17 inbred. A second drl2 allele, produced by transposon mutagenesis, interacted synergistically with drl1 mutants and reduced drl2 transcript levels. The drl genes are required for proper leaf patterning, development and cell proliferation of leaf support tissues, and for restricting auricle expansion at the midrib. The paralogous loci encode maize CRABS CLAW co-orthologs in the YABBY family of transcriptional regulators. The drl genes are coexpressed in incipient and emergent leaf primordia at the shoot apex, but not in the vegetative meristem or stem. Genome-wide association studies using maize NAM-RIL (nested association mapping-recombinant inbred line) populations indicated that the drl loci reside within quantitative trait locus regions for leaf angle, leaf width, and internode length and identified rare single nucleotide polymorphisms with large phenotypic effects for the latter two traits. This study demonstrates that drl genes control the development of key agronomic traits in maize.

Novel Loci Underlie Natural Variation in Vitamin E Levels in Maize Grain.

Tocopherols, tocotrienols, and plastochromanols (collectively termed tocochromanols) are lipid-soluble antioxidants synthesized by all plants. Their dietary intake, primarily from seed oils, provides vitamin E and other health benefits. Tocochromanol biosynthesis has been dissected in the dicot Arabidopsis thaliana, which has green, photosynthetic seeds, but our understanding of tocochromanol accumulation in major crops, whose seeds are nonphotosynthetic, remains limited. To understand the genetic control of tocochromanols in grain, we conducted a joint linkage and genome-wide association study in the 5000-line U.S. maize (Zea mays) nested association mapping panel. Fifty-two quantitative trait loci for individual and total tocochromanols were identified, and of the 14 resolved to individual genes, six encode novel activities affecting tocochromanols in plants. These include two chlorophyll biosynthetic enzymes that explain the majority of tocopherol variation, which was not predicted given that, like most major cereal crops, maize grain is nonphotosynthetic. This comprehensive assessment of natural variation in vitamin E levels in maize establishes the foundation for improving tocochromanol and vitamin E content in seeds of maize and other major cereal crops.

A Novel QTL for Root-Knot Nematode Resistance is Identified from a South African Sweet Sorghum Line.

Southern root-knot nematodes, Meloidogyne incognita, feed on the underground portions of hundreds of plant species and affect nutrient partitioning and water uptake of the host plants. Sorghum (Sorghum bicolor) is often not significantly damaged by southern root-knot nematodes (RKN) but some sorghum genotypes support greater population densities of RKN than other genotypes. These higher nematode populations increase the risk of damage to subsequently planted susceptible crops. A previous study identified a major quantitative trait locus (QTL) for RKN resistance on sorghum chromosome (chr.) 3. To maintain long-term resistance, multiple resistance genes should be pyramided in a cultivar. In this study, we identified a new source of RKN resistance, created a mapping population, and identified single-nucleotide polymorphism markers using genotyping-by-sequencing of the segregating population. Use of single-marker analysis and composite interval mapping identified a single QTL on chr. 5 that was associated with egg number and egg number per gram of root from the resistant sweet sorghum line PI 144134. This region on chr. 5 and the prior QTL on chr. 3 can be potentially moved from PI 144134 and Honey Drip, respectively, into elite sorghum germplasm via marker-assisted selection for more durable resistance.

Mapping a male-fertility restoration locus for the A4 cytoplasmic-genic male-sterility system in pearl millet using a genotyping-by-sequencing-based linkage map.

BACKGROUND: Pearl millet (Pennisetum glaucum (L.) R. Br., syn. Cenchrus americanus (L.) R. Br) is an important cereal and fodder crop in hot and arid environments. There is great potential to improve pearl millet production through hybrid breeding. Cytoplasmic male sterility (CMS) and the corresponding nuclear fertility restoration / sterility maintenance genes (Rfs) are essential tools for economic hybrid seed production in pearl millet. Mapping the Rf genes of the A4 CMS system in pearl millet would enable more efficient introgression of both dominant male-fertility restoration alleles (Rf) and their recessive male-sterility maintenance counterparts (rf). RESULTS: A high density linkage map based on single nucleotide polymorphism (SNP) markers was generated using an F2 mapping population and genotyping-by-sequencing (GBS). The parents of this cross were 'ICMA 02777' and 'ICMR 08888', which segregate for the A4 Rf locus. The linkage map consists of 460 SNP markers distributed mostly evenly and has a total length of 462 cM. The segregation ratio of male-fertile and male-sterile plants (3:1) based on pollen production (presence/absence) indicated monogenic dominant inheritance of male-fertility restoration. Correspondingly, a major quantitative trait locus (QTL) for pollen production was found on linkage group 2, with cross-validation showing a very high QTL occurrence (97%). The major QTL was confirmed using selfed seed set as phenotypic trait, though with a lower precision. However, these QTL explained only 14.5% and 9.9% of the phenotypic variance of pollen production and selfed seed set, respectively, which was below expectation. Two functional KASP markers were developed for the identified locus. CONCLUSION: This study identified a major QTL for male-fertility restoration using a GBS-based linkage map and developed KASP markers which support high-throughput screening of the haploblock. This is a first step toward marker-assisted selection of A4 male-fertility restoration and male-sterility maintenance in pearl millet.

Association mapping across numerous traits reveals patterns of functional variation in maize.

Phenotypic variation in natural populations results from a combination of genetic effects, environmental effects, and gene-by-environment interactions. Despite the vast amount of genomic data becoming available, many pressing questions remain about the nature of genetic mutations that underlie functional variation. We present the results of combining genome-wide association analysis of 41 different phenotypes in ∼ 5,000 inbred maize lines to analyze patterns of high-resolution genetic association among of 28.9 million single-nucleotide polymorphisms (SNPs) and ∼ 800,000 copy-number variants (CNVs). We show that genic and intergenic regions have opposite patterns of enrichment, minor allele frequencies, and effect sizes, implying tradeoffs among the probability that a given polymorphism will have an effect, the detectable size of that effect, and its frequency in the population. We also find that genes tagged by GWAS are enriched for regulatory functions and are ∼ 50% more likely to have a paralog than expected by chance, indicating that gene regulation and gene duplication are strong drivers of phenotypic variation. These results will likely apply to many other organisms, especially ones with large and complex genomes like maize.

Genome-wide association of carbon and nitrogen metabolism in the maize nested association mapping population.

Carbon (C) and nitrogen (N) metabolism are critical to plant growth and development and are at the basis of crop yield and adaptation. We performed high-throughput metabolite analyses on over 12,000 samples from the nested association mapping population to identify genetic variation in C and N metabolism in maize (Zea mays ssp. mays). All samples were grown in the same field and used to identify natural variation controlling the levels of 12 key C and N metabolites, namely chlorophyll a, chlorophyll b, fructose, fumarate, glucose, glutamate, malate, nitrate, starch, sucrose, total amino acids, and total protein, along with the first two principal components derived from them. Our genome-wide association results frequently identified hits with single-gene resolution. In addition to expected genes such as invertases, natural variation was identified in key C4 metabolism genes, including carbonic anhydrases and a malate transporter. Unlike several prior maize studies, extensive pleiotropy was found for C and N metabolites. This integration of field-derived metabolite data with powerful mapping and genomics resources allows for the dissection of key metabolic pathways, providing avenues for future genetic improvement.

OLE RNA protects extremophilic bacteria from alcohol toxicity.

OLE (Ornate, Large, Extremophilic) RNAs represent a recently discovered non-coding RNA class found in extremophilic anaerobic bacteria, including certain human pathogens. OLE RNAs exhibit several unusual characteristics that indicate a potentially novel function, including exceptionally high expression and localization to cell membranes via interaction with a protein partner called OLE-associated protein (OAP). In the current study, new genetic and phenotypic characteristics of OLE RNA from Bacillus halodurans C-125 were established. OLE RNA is transcribed at high levels from its own promoter under normal growth conditions and the transcript is exceptionally stable compared to most other RNAs. Expression is increased by ∼ 7-fold when cells are exposed to near lethal concentrations of short-chain alcohols such as ethanol or methanol. Strains wherein the genes for OLE and/or OAP are deleted are more susceptible to growth inhibition by alcohol and also become more sensitive to cold. Normal growth characteristics can be restored by expressing the genes for OLE and OAP from plasmids or from elsewhere on the chromosome. Our findings confirm a functional link between OLE and OAP and reveal the importance of a large non-coding RNA in the response to alcohol-induced stress.

Co-creating and implementing a novel pre-conference event to promote equity and inclusivity among academic researchers and people who use drugs.

This commentary draws on our experience organising a targeted networking event at the 10th International Conference on Health and Hepatitis in Substance Users, in Glasgow, Scotland in October 2022. The event, held the day before the conference, brought together people with lived and living experiences of drug use and early- and mid-career researchers on an equitable basis. We offer reflections, focussing on how the event promoted community-academic engagement from members of the respective groups. We provide recommendations for how conferences can organise to engage with people who use drugs-both those with lived and living experience and foster greater inclusion for all attendees.

Accessing opioid agonist treatment in prison in England and Scotland remains problematic - the views of people with lived experience.

PURPOSE: The purpose of this paper is to examine lived experiences of opioid agonist treatment (OAT) during and immediately following release from detention in prisons in England and Scotland. DESIGN/METHODOLOGY/APPROACH: Surveys were completed by serving prisoners in both countries and by those recently released from prison (England only). The survey findings were discussed in focus groups of people with lived experience. The combined findings from the surveys and focus groups were shared with an expert group of prison OAT providers and people with lived experience with the purpose of making recommendations for more accessible and effective OAT in custodial environments and continuity of OAT on release. FINDINGS: The quality and accessibility of OAT varied considerably between establishments. It was reported to be harder to access OAT in Scottish prisons. It was often hard for people in prison to get the dosage of OAT they felt they needed and it was generally harder to access buprenorphine than methadone in English prisons. Only Scottish people in prison were aware of long-lasting forms of buprenorphine. People in English prisons had mixed experiences of the help available in prison, with no improvement recorded since a 2016 study. People in Scottish prisons were more likely to rate the help available as poor. RESEARCH LIMITATIONS/IMPLICATIONS: The number of people accessed while actually in prison (73) was reduced by the impact of the pandemic, making it more difficult to access people in prison and because some were resistant to participating on the basis that they had already been consulted for a wide variety of research projects focused on the impact of COVID. The Scottish cohort (a total of 19 individuals comprising 14 survey respondents and five focus group members) is clearly too small a number on which to base robust claims about differences in OAT provision between the English and Scottish prison systems.. PRACTICAL IMPLICATIONS: The study identifies key barriers to accessing OAT in prisons and suggests key components of more user-friendly approaches. SOCIAL IMPLICATIONS: This study provides an overview of the recent lived experiences of people accessing OAT in prison and on release and offers valuable recommendations on how to make service provision more effective and consistent. ORIGINALITY/VALUE: This study provides an overview of the recent lived experiences of people accessing OAT in prison and on release in England and Scotland and offers valuable recommendations on how to make service provision more effective and consistent.

Corrigendum: Mining the Utricularia gibba genome for insulator-like elements for genetic engineering.

[This corrects the article DOI: 10.3389/fpls.2023.1279231.].

Risk of drug-related death associated with co-prescribing of gabapentinoids and Z-drugs among people receiving opioid-agonist treatment: A national retrospective cohort study.

BACKGROUND: Prescribing of gabapentinoids and Z-drug-hypnotics has increased in the population and among people receiving opioid-agonist treatment (OAT) for opioid dependence. Evidence is mixed on whether co-prescribing of sedatives such as gabapentinoids and Z-drugs during OAT increases risk of drug-related death (DRD). METHODS: We conducted a retrospective cohort study of individuals prescribed OAT between 2011 and 2020 in Scotland. Prescribing records were linked to mortality data and other healthcare datasets (sociodemographic, comorbidity). We identified episodes of treatment with gabapentinoids/Z-drugs and used multivariable quasi-Poisson regression to model associations between co-prescription and DRD risk. RESULTS: Among 46,602 individuals with 304,783 person-years of follow-up, we found that co-prescription was common, with 25 % and 34 % ever being co-prescribed gabapentinoids and Z-drugs, respectively. Gabapentinoid exposure was strongly associated (adjusted hazard ratio (aHR)=2·18, 95 % CI=1·92, 2·46) and Z-drug exposure moderately associated (aHR=1·39, 95 % CI=1·15, 1·66) with elevated risk of DRD. Gabapentinoid exposure was associated with DRD risk on and off OAT; Z-drug exposure was less strongly associated with DRD risk when on OAT. CONCLUSIONS: Co-prescription of gabapentinoids and Z-drugs is common among OAT patients. However, co-prescription is associated with increased risk of DRD. Alternatives to prescribing sedative medications to OAT patients and/or greater monitoring - if prescribed - are needed.

Introducing titratable water to all-atom molecular dynamics at constant pH.

Recent development of titratable coions has paved the way for realizing all-atom molecular dynamics at constant pH. To further improve physical realism, here we describe a technique in which proton titration of the solute is directly coupled to the interconversion between water and hydroxide or hydronium. We test the new method in replica-exchange continuous constant pH molecular dynamics simulations of three proteins, HP36, BBL, and HEWL. The calculated pKa values based on 10-ns sampling per replica have the average absolute and root-mean-square errors of 0.7 and 0.9 pH units, respectively. Introducing titratable water in molecular dynamics offers a means to model proton exchange between solute and solvent, thus opening a door to gaining new insights into the intricate details of biological phenomena involving proton translocation.

Maize seed endophytes.

Maize is a vital global crop, and each seed (kernel) hosts an ecosystem of microbes living inside it. However, we know very little about these endophytes and what their role is in plant production and physiology. In this Microreview, I summarize the major questions around maize seed endophytes, including what organisms are present, how they get there, whether and how they transmit across generations, and how they and the plant affect each other. Although several studies touch on each of these areas, ultimately there are far more questions than answers. Future priorities for research on maize seed endophytes should include understanding what adaptations allow microbes to be seed endophytes, how the host genetics and the environment affect these communities, and how maize seed endophytes ultimately contribute to the next generation of plants.