Obstetric ultrasound training programmes for midwives: A scoping review.

Background: Antenatal care is essential for all expectant mothers and assists in reducing maternal mortality rates thus addressing the Sustainable Development Goal 3. Obstetric ultrasound complements antenatal care and is used in pregnancy to identify and monitor high-risk pregnancies. However, disparities exist and in low- and middle-income countries, ultrasound services are not readily available. This contributes to maternal and neonatal morbidity and mortality within these populations. Short ultrasound training programmes for midwives can be beneficial in alleviating some of the challenges experienced. Aim: The aim of this scoping review was to identify global ultrasound education programmes for midwives. Method: Articles containing suitable keywords were retrieved from databases suitable to nursing, education and ultrasound. Themes were developed based on the articles included in the review. Results: A total of 238 articles were identified, and after the duplicates and irrelevant studies were removed, 22 articles were included. Articles were analysed and discussed under the identified themes and categories. Conclusion: It is essential that sufficient training is provided to medical professionals performing obstetric ultrasound so that adequate and safe care is offered to expectant mothers. With the introduction of ultrasound in low-resource settings, the knowledge of safety and competencies required to operate the equipment necessitate adequate training. Developed programmes have been found to meet the demands of the ever-changing workforce and allow for midwives to perform focused obstetric ultrasound examinations. Contribution: This scoping review highlighted ultrasound training programmes for midwives and provided guidance on the development of future midwifery ultrasound training programmes.

Meiotic chromosome axis remodelling is critical for meiotic recombination in Brassica rapa.

Meiosis generates genetic variation through homologous recombination (HR) that is harnessed during breeding. HR occurs in the context of meiotic chromosome axes and the synaptonemal complex. To study the role of axis remodelling in crossover (CO) formation in a crop species, we characterized mutants of the axis-associated protein ASY1 and the axis-remodelling protein PCH2 in Brassica rapa. asy1 plants form meiotic chromosome axes that fail to synapse. CO formation is almost abolished, and residual chiasmata are proportionally enriched in terminal chromosome regions, particularly in the nucleolar organizing region (NOR)-carrying chromosome arm. pch2 plants show impaired ASY1 loading and remodelling, consequently achieving only partial synapsis, which leads to reduced CO formation and loss of the obligatory CO. PCH2-independent chiasmata are proportionally enriched towards distal chromosome regions. Similarly, in Arabidopsis pch2, COs are increased towards telomeric regions at the expense of (peri-) centromeric COs compared with the wild type. Taken together, in B. rapa, axis formation and remodelling are critical for meiotic fidelity including synapsis and CO formation, and in asy1 and pch2 CO distributions are altered. While asy1 plants are sterile, pch2 plants are semi-sterile and thus PCH2 could be an interesting target for breeding programmes.

A major quantitative trait locus on chromosome A9, BnaPh1, controls homoeologous recombination in Brassica napus.

Ensuring faithful homologous recombination in allopolyploids is essential to maintain optimal fertility of the species. Variation in the ability to control aberrant pairing between homoeologous chromosomes in Brassica napus has been identified. The current study exploited the extremes of such variation to identify genetic factors that differentiate newly resynthesised B. napus, which is inherently unstable, and established B. napus, which has adapted to largely control homoeologous recombination. A segregating B. napus mapping population was analysed utilising both cytogenetic observations and high-throughput genotyping to quantify the levels of homoeologous recombination. Three quantitative trait loci (QTL) were identified that contributed to the control of homoeologous recombination in the important oilseed crop B. napus. One major QTL on BnaA9 contributed between 32 and 58% of the observed variation. This study is the first to assess homoeologous recombination and map associated QTLs resulting from deviations in normal pairing in allotetraploid B. napus. The identified QTL regions suggest candidate meiotic genes that could be manipulated in order to control this important trait and further allow the development of molecular markers to utilise this trait to exploit homoeologous recombination in a crop.

Curriculum framework for advanced practice nursing in sub-Saharan Africa: a multimethod study.

OBJECTIVES: The implementation of advanced practice nursing (APN) programmes in sub-Saharan Africa (SSA) has been difficult due to lack of SSA-specific curriculum frameworks or benchmarks to guide institutions in developing and implementing APN programmes. A few APN programmes in SSA were benchmarked on western philosophy and materials, making local ownership and sustainability challenging. This paper presents an SSA-specific concept-based APN (Child Health Nurse Practitioner, CHNP) curriculum framework developed to guide institutions in developing relevant and responsive APN curricula in order to qualify CHNP and contribute to a decreased incidence of preventable deaths of children in the SSA region. DESIGN: A sequential multimethod study design consisting of a scoping review, Delphi study, development of a framework by a curriculum team, and evaluation of the curriculum framework by faculty from 15 universities in SSA. SETTING: This study included universities from East, West, Central and Southern Africa. PARTICIPANTS: The study included international multidisciplinary health professionals and curriculum development experts from 15 universities in 10 SSA countries. RESULTS: A concept-based Advanced CHNP curriculum framework was developed. The faculty who evaluated the curriculum framework for applicability within their institutions and the SSA context unanimously stated that the framework is detailed, evidenced-based and could be adapted for other APN specialty areas. CONCLUSION: The Child Health Nurse Practitioner curriculum framework is comprehensive, context-specific and has the potential to respond to the special child healthcare needs of SSA. It is adaptable for other APN specialty programmes in SSA. Nursing leaders should lobby for funding and advocate for the introduction of the CHNP programme as a collaborative process between government, clinical services, communities and educational institutions.

Using Genome In Situ Hybridization (GISH) to Distinguish the Constituent Genomes of Brassica nigra and B. rapa in the Hybrid B. juncea.

The genome in situ hybridization (GISH) technique has become important for deciphering the organization of the constituent genomes in the allopolyploid plants that comprise many of the crop species. This technique comprises using the nuclear DNA from the constituent genomes as probes that have been labeled separately with different nucleotides that can be identified by using secondary antibodies. The Brassica family includes a range of mustard species with diverse phytochemical and morphological profile, hence making it an important plant family in agriculture. Meiosis is a specialized cellular division which brings the homologous chromosomes together and creates recombinants via pairing and synapsis during its early phase. Transfer of the genetic material within homoelog pairs creates novelty in subsequent generations which hold promise for improving the agriculture sector. This chapter is concerned with developing a GISH technique that discriminates between the constituent genomes in the allopolyploid B. juncea, in order to study meiosis.

Field cress genome mapping: Integrating linkage and comparative maps with cytogenetic analysis for rDNA carrying chromosomes.

Field cress (Lepidium campestre L.), despite its potential as a sustainable alternative oilseed plant, has been underutilized, and no prior attempts to characterize the genome at the genetic or molecular cytogenetic level have been conducted. Genetic maps are the foundation for anchoring and orienting annotated genome assemblies and positional cloning of candidate genes. Our principal goal was to construct a genetic map using integrated approaches of genetic, comparative and cytogenetic map analyses. In total, 503 F2 interspecific hybrid individuals were genotyped using 7,624 single nucleotide polymorphism markers. Comparative analysis demonstrated that ~57% of the sequenced loci in L. campestre were congruent with Arabidopsis thaliana (L.) genome and suggested a novel karyotype, which predates the ancestral crucifer karyotype. Aceto-orcein chromosome staining and fluorescence in situ hybridization (FISH) analyses confirmed that L. campestre, L. heterophyllum Benth. and their hybrids had a chromosome number of 2n = 2x = 16. Flow cytometric analysis revealed that both species possess 2C roughly 0.4 picogram DNA. Integrating linkage and comparative maps with cytogenetic map analyses assigned two linkage groups to their particular chromosomes. Future work could incorporate FISH utilizing A. thaliana mapped BAC clones to allow the chromosomes of field cress to be identified reliably.

Detecting de Novo Homoeologous Recombination Events in Cultivated Brassica napus Using a Genome-Wide SNP Array.

The heavy selection pressure due to intensive breeding of Brassica napus has created a narrow gene pool, limiting the ability to produce improved varieties through crosses between B. napus cultivars. One mechanism that has contributed to the adaptation of important agronomic traits in the allotetraploid B. napus has been chromosomal rearrangements resulting from homoeologous recombination between the constituent A and C diploid genomes. Determining the rate and distribution of such events in natural B. napus will assist efforts to understand and potentially manipulate this phenomenon. The Brassica high-density 60K SNP array, which provides genome-wide coverage for assessment of recombination events, was used to assay 254 individuals derived from 11 diverse cultivated spring type B. napus These analyses identified reciprocal allele gain and loss between the A and C genomes and allowed visualization of de novo homoeologous recombination events across the B. napus genome. The events ranged from loss/gain of 0.09 Mb to entire chromosomes, with almost 5% aneuploidy observed across all gametes. There was a bias toward sub-telomeric exchanges leading to genome homogenization at chromosome termini. The A genome replaced the C genome in 66% of events, and also featured more dominantly in gain of whole chromosomes. These analyses indicate de novo homoeologous recombination is a continuous source of variation in established Brassica napus and the rate of observed events appears to vary with genetic background. The Brassica 60K SNP array will be a useful tool in further study and manipulation of this phenomenon.

The State of Nursing Research in Ghana: An Integrative Literature Review.

INTRODUCTION: For nursing practice to be responsive to the needs of patients, it must be driven by contextual research evidence. To guide institutional and national nursing research policy, there is need to determine the quantity and quality of nursing research in Ghana. PURPOSE: The purpose of this integrative literature review was to quantify, critically evaluate, and describe nursing research publication in Ghana from January 2007 to December 2016 with regard to the country's research capacity to sustain evidence-based practice. RESULTS: Sixty (60) out of 749 articles identified from EBSCOhost, ProQuest, PubMed, Science Direct, Scopus, Wiley Online Library, and Google Scholar using three keywords (nursing, health, and Ghana) were included. A total of 60,778 human subjects were used in these studies. There were more quantitative (28) studies than qualitative (23) studies. These studies recorded 219 authors from 120 institutions, 55 of which were outside Ghana. Forty-five percent of the articles were published in journals with impact factor. There was a steady increase in publication in Ghana over the decade. A majority of the studies published in education were in curriculum implementation and evaluation. CONCLUSIONS: The increasing number of peer-reviewed nursing research publications in Ghana and the curriculum implementation and evaluation in Ghana signified an increasing capacity of the country to implement and sustain evidence-based practice. RECOMMENDATIONS: It is recommended that regular research be conducted to evaluate the responsiveness to old and new nursing programs in Ghana.

Through the eyes of the student: Best practices in clinical facilitation.

BACKGROUND: Clinical facilitation is an essential part of the undergraduate nursing curriculum. A number of studies address the issue of clinical facilitation in South Africa, but there remains a lack of knowledge and understanding regarding what students perceive as best practice in clinical facilitation of their learning. OBJECTIVE: To determine what type of clinical facilitation undergraduate students believe should be offered by clinical facilitators (nurse educators, professional nurses and clinical preceptors) in the clinical area in order to best facilitate their learning. METHOD: A qualitative, exploratory and descriptive study was conducted. Purposive sampling was performed to select nursing students from the second, third and fourth year of studies from a selected nursing education institution in Johannesburg. The sampling resulted in one focus group for each level of nursing, namely second, third and fourth year nursing students. Interviews were digitally recorded and transcribed verbatim, thematic data analysis was used and trustworthiness was ensured by applying credibility, dependability, confirmability and transferability. MAIN FINDINGS: The data revealed that participants differentiated between best practices in clinical facilitation in the clinical skills laboratory and clinical learning environment. In the clinical skills laboratory, pre-contact preparation, demonstration technique and optimising group learning were identified as best practices. In the clinical learning environment, a need for standardisation of procedures in simulation and practice, the allocation and support for students also emerged. CONCLUSION: There is a need for all nurses involved in undergraduate nursing education to reflect on how they approach clinical facilitation, in both clinical skills laboratory and clinical learning environment. There is also a need to improve consistency in clinical practices between the nursing education institution and the clinical learning environment so as to support students' adaptation to clinical practice.

A spontaneous mutation in MutL-Homolog 3 (HvMLH3) affects synapsis and crossover resolution in the barley desynaptic mutant des10.

Although meiosis is evolutionarily conserved, many of the underlying mechanisms show species-specific differences. These are poorly understood in large genome plant species such as barley (Hordeum vulgare) where meiotic recombination is very heavily skewed to the ends of chromosomes. The characterization of mutant lines can help elucidate how recombination is controlled. We used a combination of genetic segregation analysis, cytogenetics, immunocytology and 3D imaging to genetically map and characterize the barley meiotic mutant DESYNAPTIC 10 (des10). We identified a spontaneous exonic deletion in the orthologue of MutL-Homolog 3 (HvMlh3) as the causal lesion. Compared with wild-type, des10 mutants exhibit reduced recombination and fewer chiasmata, resulting in the loss of obligate crossovers and leading to chromosome mis-segregation. Using 3D structured illumination microscopy (3D-SIM), we observed that normal synapsis progression was also disrupted in des10, a phenotype that was not evident with standard confocal microscopy and that has not been reported with Mlh3 knockout mutants in Arabidopsis. Our data provide new insights on the interplay between synapsis and recombination in barley and highlight the need for detailed studies of meiosis in nonmodel species. This study also confirms the importance of early stages of prophase I for the control of recombination in large genome cereals.

Arabidopsis PCH2 Mediates Meiotic Chromosome Remodeling and Maturation of Crossovers.

Meiotic chromosomes are organized into linear looped chromatin arrays by a protein axis localized along the loop-bases. Programmed remodelling of the axis occurs during prophase I of meiosis. Structured illumination microscopy (SIM) has revealed dynamic changes in the chromosome axis in Arabidopsis thaliana and Brassica oleracea. We show that the axis associated protein ASY1 is depleted during zygotene concomitant with synaptonemal complex (SC) formation. Study of an Atpch2 mutant demonstrates this requires the conserved AAA+ ATPase, PCH2, which localizes to the sites of axis remodelling. Loss of PCH2 leads to a failure to deplete ASY1 from the axes and compromizes SC polymerisation. Immunolocalization of recombination proteins in Atpch2 indicates that recombination initiation and CO designation during early prophase I occur normally. Evidence suggests that CO interference is initially functional in the mutant but there is a defect in CO maturation following designation. This leads to a reduction in COs and a failure to form COs between some homologous chromosome pairs leading to univalent chromosomes at metaphase I. Genetic analysis reveals that CO distribution is also affected in some chromosome regions. Together these data indicate that the axis remodelling defect in Atpch2 disrupts normal patterned formation of COs.

The activities of hospital nursing unit managers and quality of patient care in South African hospitals: a paradox?

BACKGROUND: Improving the quality of health care is central to the proposed health care reforms in South Africa. Nursing unit managers play a key role in coordinating patient care activities and in ensuring quality care in hospitals. OBJECTIVE: This paper examines whether the activities of nursing unit managers facilitate the provision of quality patient care in South African hospitals. METHODS: During 2011, a cross-sectional, descriptive study was conducted in nine randomly selected hospitals (six public, three private) in two South African provinces. In each hospital, one of each of the medical, surgical, paediatric, and maternity units was selected (n=36). Following informed consent, each unit manager was observed for a period of 2 hours on the survey day and the activities recorded on a minute-by-minute basis. The activities were entered into Microsoft Excel, coded into categories, and analysed according to the time spent on activities in each category. The observation data were complemented by semi-structured interviews with the unit managers who were asked to recall their activities on the day preceding the interview. The interviews were analysed using thematic content analysis. RESULTS: The study found that nursing unit managers spent 25.8% of their time on direct patient care, 16% on hospital administration, 14% on patient administration, 3.6% on education, 13.4% on support and communication, 3.9% on managing stock and equipment, 11.5% on staff management, and 11.8% on miscellaneous activities. There were also numerous interruptions and distractions. The semi-structured interviews revealed concordance between unit managers' recall of the time spent on patient care, but a marked inflation of their perceived time spent on hospital administration. CONCLUSION: The creation of an enabling practice environment, supportive executive management, and continuing professional development are needed to enable nursing managers to lead the provision of consistent and high-quality patient care.

Social accountability and nursing education in South Africa.

BACKGROUND: There is global emphasis on transforming health workforce education in support of universal health coverage. OBJECTIVE: This paper uses a social accountability framework, specifically the World Health Organization's six building blocks for transformative education, to explore key informants' perspectives on nursing education in South Africa. METHODS: Using a snowballing sampling technique, 44 key informants were selected purposively on the basis of their expertise or knowledge of the research area. Semi-structured interviews were conducted with the key informants after informed consent had been obtained. The interviews were analysed using template analysis. RESULTS: South Africa has strategic plans on human resources for health and nursing education, training, and practice and has a well-established system of regulation and accreditation of nursing education through the South African Nursing Council (SANC). Key informants criticised the following: the lack of national staffing norms; sub-optimal governance by both the SANC and the Department of Health; outdated curricula that are unresponsive to population and health system needs; lack of preparedness of nurse educators; and the unsuitability of the majority of nursing students. These problems are exacerbated by a perceived lack of prioritisation of nursing, resource constraints in both the nursing education institutions and the health training facilities, and general implementation inertia. CONCLUSION: Social accountability, which is an essential component of transformative education, necessitates that attention be paid to the issues of governance, responsive curricula, educator preparedness, and appropriate student recruitment and selection.

Absence of SUN1 and SUN2 proteins in Arabidopsis thaliana leads to a delay in meiotic progression and defects in synapsis and recombination.

The movement of chromosomes during meiosis involves location of their telomeres at the inner surface of the nuclear envelope. Sad1/UNC-84 (SUN) domain proteins are inner nuclear envelope proteins that are part of complexes linking cytoskeletal elements with the nucleoskeleton, connecting telomeres to the force-generating mechanism in the cytoplasm. These proteins play a conserved role in chromosome dynamics in eukaryotes. Homologues of SUN domain proteins have been identified in several plant species. In Arabidopsis thaliana, two proteins that interact with each other, named AtSUN1 and AtSUN2, have been identified. Immunolocalization using antibodies against AtSUN1 and AtSUN2 proteins revealed that they were associated with the nuclear envelope during meiotic prophase I. Analysis of the double mutant Atsun1-1 Atsun2-2 has revealed severe meiotic defects, namely a delay in the progression of meiosis, absence of full synapsis, the presence of unresolved interlock-like structures, and a reduction in the mean cell chiasma frequency. We propose that in Arabidopsis thaliana, overlapping functions of SUN1 and SUN2 ensure normal meiotic recombination and synapsis.

The kinesin AtPSS1 promotes synapsis and is required for proper crossover distribution in meiosis.

Meiotic crossovers (COs) shape genetic diversity by mixing homologous chromosomes at each generation. CO distribution is a highly regulated process. CO assurance forces the occurrence of at least one obligatory CO per chromosome pair, CO homeostasis smoothes out the number of COs when faced with variation in precursor number and CO interference keeps multiple COs away from each other along a chromosome. In several organisms, it has been shown that cytoskeleton forces are transduced to the meiotic nucleus via KASH- and SUN-domain proteins, to promote chromosome synapsis and recombination. Here we show that the Arabidopsis kinesin AtPSS1 plays a major role in chromosome synapsis and regulation of CO distribution. In Atpss1 meiotic cells, chromosome axes and DNA double strand breaks (DSBs) appear to form normally but only a variable portion of the genome synapses and is competent for CO formation. Some chromosomes fail to form the obligatory CO, while there is an increased CO density in competent regions. However, the total number of COs per cell is unaffected. We further show that the kinesin motor domain of AtPSS1 is required for its meiotic function, and that AtPSS1 interacts directly with WIP1 and WIP2, two KASH-domain proteins. Finally, meiocytes missing AtPSS1 and/or SUN proteins show similar meiotic defects suggesting that AtPSS1 and SUNs act in the same pathway. This suggests that forces produced by the AtPSS1 kinesin and transduced by WIPs/SUNs, are required to authorize complete synapsis and regulate maturation of recombination intermediates into COs. We suggest that a form of homeostasis applies, which maintains the total number of COs per cell even if only a part of the genome is competent for CO formation.

The synaptonemal complex protein ZYP1 is required for imposition of meiotic crossovers in barley.

In many cereal crops, meiotic crossovers predominantly occur toward the ends of chromosomes and 30 to 50% of genes rarely recombine. This limits the exploitation of genetic variation by plant breeding. Previous reports demonstrate that chiasma frequency can be manipulated in plants by depletion of the synaptonemal complex protein ZIPPER1 (ZYP1) but conflict as to the direction of change, with fewer chiasmata reported in Arabidopsis thaliana and more crossovers reported for rice (Oryza sativa). Here, we use RNA interference (RNAi) to reduce the amount of ZYP1 in barley (Hordeum vulgare) to only 2 to 17% of normal zygotene levels. In the ZYP1(RNAi) lines, fewer than half of the chromosome pairs formed bivalents at metaphase and many univalents were observed, leading to chromosome nondisjunction and semisterility. The number of chiasmata per cell was reduced from 14 in control plants to three to four in the ZYP1-depleted lines, although the localization of residual chiasmata was not affected. DNA double-strand break formation appeared normal, but the recombination pathway was defective at later stages. A meiotic time course revealed a 12-h delay in prophase I progression to the first labeled tetrads. Barley ZYP1 appears to function similarly to ZIP1/ZYP1 in yeast and Arabidopsis, with an opposite effect on crossover number to ZEP1 in rice, another member of the Poaceae.

SHUGOSHINs and PATRONUS protect meiotic centromere cohesion in Arabidopsis thaliana.

In meiosis, chromosome cohesion is maintained by the cohesin complex, which is released in a two-step manner. At meiosis I, the meiosis-specific cohesin subunit Rec8 is cleaved by the protease Separase along chromosome arms, allowing homologous chromosome segregation. Next, in meiosis II, cleavage of the remaining centromere cohesin results in separation of the sister chromatids. In eukaryotes, protection of centromeric cohesion in meiosis I is mediated by SHUGOSHINs (SGOs). The Arabidopsis genome contains two SGO homologs. Here we demonstrate that Atsgo1 mutants show a premature loss of cohesion of sister chromatid centromeres at anaphase I and that AtSGO2 partially rescues this loss of cohesion. In addition to SGOs, we characterize PATRONUS which is specifically required for the maintenance of cohesion of sister chromatid centromeres in meiosis II. In contrast to the Atsgo1 Atsgo2 double mutant, patronus T-DNA insertion mutants only display loss of sister chromatid cohesion after meiosis I, and additionally show disorganized spindles, resulting in defects in chromosome segregation in meiosis. This leads to reduced fertility and aneuploid offspring. Furthermore, we detect aneuploidy in sporophytic tissue, indicating a role for PATRONUS in chromosome segregation in somatic cells. Thus, ploidy stability is preserved in Arabidopsis by PATRONUS during both meiosis and mitosis.

CDKG1 protein kinase is essential for synapsis and male meiosis at high ambient temperature in Arabidopsis thaliana.

The Arabidopsis cyclin-dependent kinase G (CDKG) gene defines a clade of cyclin-dependent protein kinases related to CDK10 and CDK11, as well as to the enigmatic Ph1-related kinases that are implicated in controlling homeologous chromosome pairing in wheat. Here we demonstrate that the CDKG1/CYCLINL complex is essential for synapsis and recombination during male meiosis. A transfer-DNA insertional mutation in the cdkg1 gene leads to a temperature-sensitive failure of meiosis in late Zygotene/Pachytene that is associated with defective formation of the synaptonemal complex, reduced bivalent formation and crossing over, and aneuploid gametes. An aphenotypic insertion in the cyclin L gene, a cognate cyclin for CDKG, strongly enhances the phenotype of cdkg1-1 mutants, indicating that this cdk-cyclin complex is essential for male meiosis. Since CYCLINL, CDKG, and their mammalian homologs have been previously shown to affect mRNA processing, particularly alternative splicing, our observations also suggest a mechanism to explain the widespread phenomenon of thermal sensitivity in male meiosis.

Spatiotemporal asymmetry of the meiotic program underlies the predominantly distal distribution of meiotic crossovers in barley.

Meiosis involves reciprocal exchange of genetic information between homologous chromosomes to generate new allelic combinations. In cereals, the distribution of genetic crossovers, cytologically visible as chiasmata, is skewed toward the distal regions of the chromosomes. However, many genes are known to lie within interstitial/proximal regions of low recombination, creating a limitation for breeders. We investigated the factors underlying the pattern of chiasma formation in barley (Hordeum vulgare) and show that chiasma distribution reflects polarization in the spatiotemporal initiation of recombination, chromosome pairing, and synapsis. Consequently, meiotic progression in distal chromosomal regions occurs in coordination with the chromatin cycles that are a conserved feature of the meiotic program. Recombination initiation in interstitial and proximal regions occurs later than distal events, is not coordinated with the cycles, and rarely progresses to form chiasmata. Early recombination initiation is spatially associated with early replicating, euchromatic DNA, which is predominately found in distal regions. We demonstrate that a modest temperature shift is sufficient to alter meiotic progression in relation to the chromosome cycles. The polarization of the meiotic processes is reduced and is accompanied by a shift in chiasma distribution with an increase in interstitial and proximal chiasmata, suggesting a potential route to modify recombination in cereals.

Inter-homolog crossing-over and synapsis in Arabidopsis meiosis are dependent on the chromosome axis protein AtASY3.

In this study we have analysed AtASY3, a coiled-coil domain protein that is required for normal meiosis in Arabidopsis. Analysis of an Atasy3-1 mutant reveals that loss of the protein compromises chromosome axis formation and results in reduced numbers of meiotic crossovers (COs). Although the frequency of DNA double-strand breaks (DSBs) appears moderately reduced in Atasy3-1, the main recombination defect is a reduction in the formation of COs. Immunolocalization studies in wild-type meiocytes indicate that the HORMA protein AtASY1, which is related to Hop1 in budding yeast, forms hyper-abundant domains along the chromosomes that are spatially associated with DSBs and early recombination pathway proteins. Loss of AtASY3 disrupts the axial organization of AtASY1. Furthermore we show that the AtASY3 and AtASY1 homologs BoASY3 and BoASY1, from the closely related species Brassica oleracea, are co-immunoprecipitated from meiocyte extracts and that AtASY3 interacts with AtASY1 via residues in its predicted coiled-coil domain. Together our results suggest that AtASY3 is a functional homolog of Red1. Since studies in budding yeast indicate that Red1 and Hop1 play a key role in establishing a bias to favor inter-homolog recombination (IHR), we propose that AtASY3 and AtASY1 may have a similar role in Arabidopsis. Loss of AtASY3 also disrupts synaptonemal complex (SC) formation. In Atasy3-1 the transverse filament protein AtZYP1 forms small patches rather than a continuous SC. The few AtMLH1 foci that remain in Atasy3-1 are found in association with the AtZYP1 patches. This is sufficient to prevent the ectopic recombination observed in the absence of AtZYP1, thus emphasizing that in addition to its structural role the protein is important for CO formation.