Comparison of factors associated with postpartum depression from two cohorts of nurses: the Korea Nurses' Health Study and the Nurses' Health Study 3.

OBJECTIVES: This study aimed to identify whether differences exist in postpartum depression (PPD) in US and Korean nurses and its related factors. Identifying occupational and personal factors that underlie potential differences will be helpful for women's occupational health. METHODS: Baseline and postpartum survey data from employed nurses in the Korea Nurses' Health Study and Nurses' Health Study 3 (1244 Korean; 2742 US nurses) were analysed. Postpartum data collection was done via online survey. PPD was analysed based on cultural validation from prior studies using the Edinburgh Postnatal Depression Scale (cut-off of 10 for Korea and 13 for USA); depressive symptoms prior to pregnancy and childbirth, general characteristics and sleep satisfaction were also measured. Descriptive statistics, χ2 tests and t-tests and multivariate ordinal logistic regression analysis were performed. RESULTS: 45.9% of Korean participants had clinical symptoms of PPD (≥10), whereas US participants presented with 3.4% (≥13). Prior depressive symptoms were also higher in Korean participants (22.5%) compared with their US counterparts (4.5%). Prior depressive symptoms and poor sleep satisfaction were significant risk factors of PPD in both cohort groups, and vaginal birth was an additional influencing factor in Korean participants. CONCLUSIONS: Differences in PPD rates and related factors suggest the role of stress, cultural variation and differing work systems. Nurses and other women shift-workers noted to have depressive symptoms before and during pregnancy and exhibit PPD symptoms should especially be followed closely and offered supportive mental health services that include greater flexibility in returning to work.

Genomic selection with fixed-effect markers improves the prediction accuracy for Capsaicinoid contents in Capsicum annuum.

Capsaicinoids provide chili peppers (Capsicum spp.) with their characteristic pungency. Several structural and transcription factor genes are known to control capsaicinoid contents in pepper. However, many other genes also regulating capsaicinoid contents remain unknown, making it difficult to develop pepper cultivars with different levels of capsaicinoids. Genomic selection (GS) uses genome-wide random markers (including many in undiscovered genes) for a trait to improve selection efficiency. In this study, we predicted the capsaicinoid contents of pepper breeding lines using several GS models trained with genotypic and phenotypic data from a training population. We used a core collection of 351 Capsicum accessions and 96 breeding lines as training and testing populations, respectively. To obtain the optimal number of single nucleotide polymorphism (SNP) markers for GS, we tested various numbers of genome-wide SNP markers based on linkage disequilibrium. We obtained the highest mean prediction accuracy (0.550) for different models using 3294 SNP markers. Using this marker set, we conducted GWAS and selected 25 markers that were associated with capsaicinoid biosynthesis genes and quantitative trait loci for capsaicinoid contents. Finally, to develop more accurate prediction models, we obtained SNP markers from GWAS as fixed-effect markers for GS, where 3294 genome-wide SNPs were employed. When four to five fixed-effect markers from GWAS were used as fixed effects, the RKHS and RR-BLUP models showed accuracies of 0.696 and 0.689, respectively. Our results lay the foundation for developing pepper cultivars with various capsaicinoid levels using GS for capsaicinoid contents.

High-quality chromosome-scale genomes facilitate effective identification of large structural variations in hot and sweet peppers.

Pepper (Capsicum annuum) is an important vegetable crop that has been subjected to intensive breeding, resulting in limited genetic diversity, especially for sweet peppers. Previous studies have reported pepper draft genome assemblies using short read sequencing, but their capture of the extent of large structural variants (SVs), such as presence-absence variants (PAVs), inversions, and copy-number variants (CNVs) in the complex pepper genome falls short. In this study, we sequenced the genomes of representative sweet and hot pepper accessions by long-read and/or linked-read methods and advanced scaffolding technologies. First, we developed a high-quality reference genome for the sweet pepper cultivar 'Dempsey' and then used the reference genome to identify SVs in 11 other pepper accessions and constructed a graph-based pan-genome for pepper. We annotated an average of 42 972 gene families in each pepper accession, defining a set of 19 662 core and 23 115 non-core gene families. The new pepper pan-genome includes informative variants, 222 159 PAVs, 12 322 CNVs, and 16 032 inversions. Pan-genome analysis revealed PAVs associated with important agricultural traits, including potyvirus resistance, fruit color, pungency, and pepper fruit orientation. Comparatively, a large number of genes are affected by PAVs, which is positively correlated with the high frequency of transposable elements (TEs), indicating TEs play a key role in shaping the genomic landscape of peppers. The datasets presented herein provide a powerful new genomic resource for genetic analysis and genome-assisted breeding for pepper improvement.

Identification of Genetic Factors Controlling the Formation of Multiple Flowers Per Node in Pepper (Capsicum spp.).

Flower production provides the foundation for crop yield and increased profits. Capsicum annuum is a pepper species with a sympodial shoot structure with solitary flowers. By contrast, C. chinense produces multiple flowers per node. C. annuum accounts for 80% of pepper production worldwide. The identification of C. chinense genes that control multiple flowers and their transfer into C. annuum may open the way to increasing fruit yield. In this study, we dissected the genetic factors were dissected controlling the multiple-flower-per-node trait in Capsicum. 85 recombinant inbred lines (RILs) between the contrasting C. annuum 'TF68' and C. chinense 'Habanero' accessions were phenotyped and genotyped. Quantitative Trait Loci (QTL) analysis identified four novel QTLs on chromosomes 1, 2, 7, and 11 that accounted for 65% of the total phenotypic variation. Genome-wide association study was also performed on a panel of 276 genotyped and phenotyped C. annuum accessions, which revealed 28 regions significantly associated with the multiple-flower trait, of which three overlapped the identified QTLs. Five candidate genes involved in the development of the shoot and flower meristems were identified and these genes could cause multiple flowers per node in pepper. These results contribute to our understanding of multiple flower formation in Capsicum and will be useful to develop high-yielding cultivars.

Fine Mapping and Candidate Gene Identification for the CapUp Locus Controlling Fruit Orientation in Pepper (Capsicum spp.).

The orientation of fruits is a distinguishing morphological feature of pepper (Capsicum spp.) varieties. The pendent (downward curved) growth of the fruit stalks, known as pedicels, is highly correlated with fruit weight and pedicel length. A previous genetic analysis revealed that the pendent fruit orientation is governed by a dominant gene, and incomplete inheritance is also observed in some Capsicum accessions. To identify and localize this gene, a single quantitative trait locus (QTL) analysis was performed on one F2 and two recombinant inbred line (RIL) populations, and a genome-wide association study (GWAS) was performed using a core collection. Common QTL regions associated with fruit orientation were detected on chromosome 12. A total of 187,966 SNPs were identified in a genotyping-by-sequencing (GBS) for GWAS analysis of 196 Capsicum annuum, 25 Capsicum baccatum, 21 Capsicum chinense, and 14 Capsicum frutescens accessions, representing the germplasm collection of South Korea. The results of these analyses enabled us to narrow down the CapUp region of interest to 200-250 Mbp on chromosome 12. Seven candidate genes were found to be located between two markers that were completely cosegregated with the fruit orientation phenotype. The findings and markers developed in this study will be helpful for additional understanding of pepper fruit development and breeding for fruit orientation.

Identification of an Allelic Variant of the CsOr Gene Controlling Fruit Endocarp Color in Cucumber (Cucumis sativus L.) Using Genotyping-By-Sequencing (GBS) and Whole-Genome Sequencing.

The cucumber is a major vegetable crop around the world. Fruit flesh color is an important quality trait in cucumber and flesh color mainly depends on the relative content of ß-carotene in the fruits. The ß-carotene serves as a precursor of vitamin A, which has dietary benefits for human health. Cucumbers with orange flesh contain a higher amount of ß-carotene than white fruit flesh. Therefore, development of orange-fleshed cucumber varieties is gaining attention for improved nutritional benefits. In this study, we performed genotyping-by-sequencing (GBS) based on genetic mapping and whole-genome sequencing to identify the orange endocarp color gene in the cucumber breeding line, CS-B. Genetic mapping, genetic sequencing, and genetic segregation analyses showed that a single recessive gene (CsaV3_6G040750) encodes a chaperone DnaJ protein (DnaJ) protein at the Cucumis sativus(CsOr) locus was responsible for the orange endocarp phenotype in the CS-B line. The Or gene harbored point mutations T13G and T17C in the first exon of the coding region, resulting in serine to alanine at position 13 and isoleucine to threonine at position 17, respectively. CS-B line displayed increased ß-carotene content in the endocarp tissue, corresponding to elevated expression of CsOr gene at fruit developmental stages. Identifying novel missense mutations in the CsOr gene could provide new insights into the role of Or mechanism of action for orange fruit flesh in cucumber and serve as a valuable resource for developing ß-carotene-rich cucumbers varieties with increased nutritional benefits.

Genomic Selection for Prediction of Fruit-Related Traits in Pepper (Capsicum spp.).

Pepper (Capsicum spp.) fruit-related traits are critical determinants of quality. These traits are controlled by quantitatively inherited genes for which marker-assisted selection (MAS) has proven insufficiently effective. Here, we evaluated the potential of genomic selection, in which genotype and phenotype data for a training population are used to predict phenotypes of a test population with only genotype data, for predicting fruit-related traits in pepper. We measured five fruit traits (fruit length, fruit shape, fruit width, fruit weight, and pericarp thickness) in 351 accessions from the pepper core collection, including 229 Capsicum annuum, 48 Capsicum baccatum, 48 Capsicum chinense, 25 Capsicum frutescens, and 1 Capsicum chacoense in 4 years at two different locations and genotyped these accessions using genotyping-by-sequencing. Among the whole core collection, considering its genetic distance and sexual incompatibility, we only included 302 C. annum complex (229 C. annuum, 48 C. chinense, and 25 C. frutescens) into further analysis. We used phenotypic and genotypic data to investigate genomic prediction models, marker density, and effects of population structure. Among 10 genomic prediction methods tested, Reproducing Kernel Hilbert Space (RKHS) produced the highest prediction accuracies (measured as correlation between predicted values and observed values) across the traits, with accuracies of 0.75, 0.73, 0.84, 0.83, and 0.82 for fruit length, fruit shape, fruit width, fruit weight, and pericarp thickness, respectively. Overall, prediction accuracies were positively correlated with the number of markers for fruit traits. We tested our genomic selection models in a separate population of recombinant inbred lines derived from two parental lines from the core collection. Despite the large difference in genetic diversity between the training population and the test population, we obtained moderate prediction accuracies of 0.32, 0.34, 0.50, and 0.48 for fruit length, fruit shape, fruit width, and fruit weight, respectively. This use of genomic selection for fruit-related traits demonstrates the potential use of core collections and genomic selection as tools for crop improvement.

Uncovering Candidate Genes Controlling Major Fruit-Related Traits in Pepper via Genotype-by-Sequencing Based QTL Mapping and Genome-Wide Association Study.

All modern pepper accessions are products of the domestication of wild Capsicum species. However, due to the limited availability of genome-wide association study (GWAS) data and selection signatures for various traits, domestication-related genes have not been identified in pepper. Here, to address this problem, we obtained data for major fruit-related domestication traits (fruit length, width, weight, pericarp thickness, and fruit position) using a highly diverse panel of 351 pepper accessions representing the worldwide Capsicum germplasm. Using a genotype-by-sequencing (GBS) method, we developed 187,966 genome-wide high-quality SNP markers across 230 C. annuum accessions. Linkage disequilibrium (LD) analysis revealed that the average length of the LD blocks was 149 kb. Using GWAS, we identified 111 genes that were linked to 64 significant LD blocks. We cross-validated the GWAS results using 17 fruit-related QTLs and identified 16 causal genes thought to be associated with fruit morphology-related domestication traits, with molecular functions such as cell division and expansion. The significant LD blocks and candidate genes identified in this study provide unique molecular footprints for deciphering the domestication history of Capsicum. Further functional validation of these candidate genes should accelerate the cloning of genes for major fruit-related traits in pepper.

Population Structure and Genetic Diversity of Cucurbita moschata Based on Genome-Wide High-Quality SNPs.

Pumpkins (Cucurbita moschata) are one of the most important economic crops in genus Cucurbita worldwide. They are a popular food resource and an important rootstock resource for various Cucurbitaceae. Especially, C. moschata is widely used as a rootstock for the commercial production of bloomless cucumbers in East Asia. Since the genetic diversity of the commercial rootstock varieties is narrow, there has been an increasing demand for the trait development of abiotic and biotic stress tolerance breeding. In this study, 2071 high-quality SNPs that were distributed evenly across 20 chromosomes of pumpkins were discovered through the genotyping-by-sequencing (GBS) analysis of 610 accessions of C. moschata germplasm with a global origin. Using these SNPs, various analyses of the genetic diversity and the population structure were performed. Three subgroups were clustered from the germplasm collection, which included East Asia, Africa, and America, and these areas were included the most in each subgroup. Among those groups, accessions from Africa and South Asia showed the highest genetic diversity, which was followed by the Mexico accessions. This result reflected that large gene pools that consist of various native landraces have been conserved in those of countries. Based on the genetic diversity, we finally constructed the C. moschata core collection, which included 67 representative accessions from the 610 germplasms. Five morphological traits that are important in commercial grafting and rootstock seed production, which include the cotyledon length, the cotyledon width, the hypocotyl length, the internode length, and the number of female flowers, were investigated for three years and used to confirm the validity of the core collection selection. The results are expected to provide valuable information about the genetic structure of the worldwide C. moschata germplasm and help to create new gene pools to develop genetically diverse rootstock breeding materials.

Mitotypes Based on Structural Variation of Mitochondrial Genomes Imply Relationships With Morphological Phenotypes and Cytoplasmic Male Sterility in Peppers.

Plant mitochondrial genomes characteristically contain extensive structural variation that can be used to define and classify cytoplasm types. We developed markers based on structural variation in the mitochondrial genomes of fertile and cytoplasmic male sterility (CMS) pepper lines and applied them to a panel of Capsicum accessions. We designed a total of 20 sequence characterized amplified region (SCAR) markers based on DNA rearrangement junctions or cytoplasm-specific segments that did not show high similarity to any nuclear mitochondrial DNA segments. We used those markers to classify the mitotypes of 96 C. annuum accessions into 15 groups. Precise genotyping of other Capsicum species (C. frutescens, C. chinense, and C. baccatum) was hampered because of various stoichiometric levels of marker amplicons. We developed a multiplex PCR system based on four of the markers that efficiently classified the C. annuum accessions into five mitotype groups. Close relationships between specific mitotypes and morphological phenotypes implied that diversification or domestication of C. annuum germplasm might have been accompanied by structural rearrangements of mitochondrial DNA or the selection of germplasms with specific mitotypes. Meanwhile, CMS lines shared the same amplification profile of markers with another mitotype. Further analysis using mitochondrial DNA (mtDNA) markers based on single-nucleotide polymorphisms (SNPs) or insertions and deletions (InDels) and CMS-specific open reading frames (orfs) provided new information about the origin of the CMS-specific mitotype and evaluation of candidates for CMS-associated genes, respectively.

Identifying candidate genes for Phytophthora capsici resistance in pepper (Capsicum annuum) via genotyping-by-sequencing-based QTL mapping and genome-wide association study.

Phytophthora capsici (Leon.) is a globally prevalent, devastating oomycete pathogen that causes root rot in pepper (Capsicum annuum). Several studies have identified quantitative trait loci (QTL) underlying resistance to P. capsici root rot (PcRR). However, breeding for pepper cultivars resistant to PcRR remains challenging due to the complexity of PcRR resistance. Here, we combined traditional QTL mapping with GWAS to broaden our understanding of PcRR resistance in pepper. Three major-effect loci (5.1, 5.2, and 5.3) conferring broad-spectrum resistance to three isolates of P. capsici were mapped to pepper chromosome P5. In addition, QTLs with epistatic interactions and minor effects specific to isolate and environment were detected on other chromosomes. GWAS detected 117 significant SNPs across the genome associated with PcRR resistance, including SNPs on chromosomes P5, P7, and P11 that colocalized with the QTLs identified here and in previous studies. Clusters of candidate nucleotide-binding site-leucine-rich repeat (NBS-LRR) and receptor-like kinase (RLK) genes were predicted within the QTL and GWAS regions; such genes often function in disease resistance. These candidate genes lay the foundation for the molecular dissection of PcRR resistance. SNP markers associated with QTLs for PcRR resistance will be useful for marker-assisted breeding and genomic selection in pepper breeding.

Genetic diversity and population structure of Ethiopian Capsicum germplasms.

We established a collection of 142 Capsicum genotypes from different geographical areas of Ethiopia with the aim of capturing genetic diversity. Morphological traits and high-resolution melting analysis distinguished one Capsicum baccatum, nine Capsicum frutescens and 132 Capsicum annuum accessions in the collection. Measurement of plant growth parameters revealed variation between germplasms in parameters including plant height, stem thickness, internode length, number of side branches, fruit width, and fruit length. Broad-sense heritability was maximum for fruit weight, followed by length and width of leaves. We used genotyping by sequencing (GBS) to identify single-nucleotide polymorphisms (SNPs) in the panel of 142 Capsicum germplasms and found 2,831,791 genome-wide SNP markers. Among these, we selected 53,284 high-quality SNPs and used them to estimate the level of genetic diversity, population structure, and phylogenetic relationships. From model-based ancestry analysis, the phylogenetic tree and principal-coordinate analysis (PCoA), we identified two distinct genetic populations: one comprising 132 C. annuum accessions and the other comprising the nine C. frutescens accessions. GWAS analysis detected 509 SNP markers that were significantly associated with fruit-, stem- and leaf-related traits. This is the first comprehensive report of the analysis of genetic variation in Ethiopian Capsicum species involving a large number of accessions. The results will help breeders utilize the germplasm collection to improve existing commercial cultivars.

Single-molecule real-time sequencing reveals diverse allelic variations in carotenoid biosynthetic genes in pepper (Capsicum spp.).

The diverse colours of mature pepper (Capsicum spp.) fruit result from the accumulation of different carotenoids. The carotenoid biosynthetic pathway has been well elucidated in Solanaceous plants, and analysis of candidate genes involved in this process has revealed variations in carotenoid biosynthetic genes in Capsicum spp. However, the allelic variations revealed by previous studies could not fully explain the variation in fruit colour in Capsicum spp. due to technical difficulties in detecting allelic variation in multiple candidate genes in numerous samples. In this study, we uncovered allelic variations in six carotenoid biosynthetic genes, including phytoene synthase (PSY1, PSY2), lycopene ß-cyclase, ß-carotene hydroxylase, zeaxanthin epoxidase and capsanthin-capsorubin synthase (CCS) genes, in 94 pepper accessions by single-molecule real-time (SMRT) sequencing. To investigate the relationship between allelic variations in the candidate genes and differences in fruit colour, we performed ultra-performance liquid chromatography analysis using 43 accessions representing each allelic variation. Different combinations of dysfunctional mutations in PSY1 and CCS could explain variation in the compositions and levels of carotenoids in the accessions examined in this study. Our results demonstrate that SMRT sequencing technology can be used to rapidly identify allelic variation in target genes in various germplasms. The newly identified allelic variants will be useful for pepper breeding and for further analysis of carotenoid biosynthesis pathways.

Gastroesophageal reflux disease and its related factors among women of reproductive age: Korea Nurses' Health Study.

BACKGROUND: Recently, the number of patients diagnosed with gastroesophageal reflux disease (GERD) has increased in Korea. Risk factors of GERD include age, sex, medication use, lack of physical exercise, increased psychological stress, low or high body mass index (BMI), unhealthy eating habits, increased alcohol consumption, and cigarette smoking. However, few studies examined the major factors affecting GERD in women of childbearing age. Therefore, this study assessed the risk factors of GERD among 20,613 female nurses of reproductive age using data from the Korea Nurses' Health Study. METHODS: Participants were recruited from July 2013 to November 2014. They provided their history of GERD 1 year prior to data collection, along with information on their demographic characteristics, health-related behaviors, diet, medical history, and physical and psychological factors. Of the total sample, 1184 individuals with GERD diagnosed in the year prior to the study were identified. Propensity score matching was used for analysis. RESULTS: Cigarette smoking, increased alcohol consumption, low or high BMI, depression, and increased psychosocial stress were associated with the prevalence of GERD among Korean young women. Multivariate ordinal logistic regression analysis revealed significant positive relationships between GERD and being a former smoker; having a low (< 18.5 kg/m2) or high BMI (> 23 kg/m2); and having mild, moderate, moderately severe, and severe depression. CONCLUSIONS: Smoking, BMI, and depression were associated with GERD. To reduce this risk among female nurses, intervention strategies are required to help nurses maintain a normal weight and manage their depression.

Weight change and risk of uterine leiomyomas: Korea Nurses' Health Study.

OBJECTIVE: This study examined the associations between anthropometric measures and uterine leiomyomas. METHODS: This study included a total of 5,062 women (median age of 35.5 years) who had experienced pregnancy and, of these women, 210 reported a diagnosis of uterine leiomyomas within the past 2 years prior to baseline in the Korea Nurses' Health Study. Participants were asked about their anthropometric factors. The odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated using logistic regression models. RESULTS: Mean body mass index (BMI) was 21.8 kg/m2 among non-cases. An increase in weight from the age of 18 years to the present was associated with increased risk of uterine leiomyomas (p for trend = .002); compared to women whose weight remained stable, the multivariate ORs (95% CIs) were 1.84 (1.22-2.76) for weight gain of 5-10 kg and 2.00 (1.25-3.20) for weight gain of more than 10 kg since age 18. A similar pattern was observed when the analysis was limited to women with a BMI of 18.5-25 kg/m2. Current weight was associated with higher odds of uterine leiomyomas. No associations were found for body size in childhood or in adolescence, weight at age 18, current BMI, or current body size. CONCLUSIONS: Weight gain in adulthood was associated with increased risk of uterine leiomyomas in Korean women, even in those with normal weight.

QTL mapping and GWAS reveal candidate genes controlling capsaicinoid content in Capsicum.

Capsaicinoids are unique compounds produced only in peppers (Capsicum spp.). Several studies using classical quantitative trait loci (QTLs) mapping and genomewide association studies (GWAS) have identified QTLs controlling capsaicinoid content in peppers; however, neither the QTLs common to each population nor the candidate genes underlying them have been identified due to the limitations of each approach used. Here, we performed QTL mapping and GWAS for capsaicinoid content in peppers using two recombinant inbred line (RIL) populations and one GWAS population. Whole-genome resequencing and genotyping by sequencing (GBS) were used to construct high-density single nucleotide polymorphism (SNP) maps. Five QTL regions on chromosomes 1, 2, 3, 4 and 10 were commonly identified in both RIL populations over multiple locations and years. Furthermore, a total of 109 610 SNPs derived from two GBS libraries were used to analyse the GWAS population consisting of 208 C. annuum-clade accessions. A total of 69 QTL regions were identified from the GWAS, 10 of which were co-located with the QTLs identified from the two biparental populations. Within these regions, we were able to identify five candidate genes known to be involved in capsaicinoid biosynthesis. Our results demonstrate that QTL mapping and GBS-GWAS represent a powerful combined approach for the identification of loci controlling complex traits.

Molecular Mapping of PMR1, a Novel Locus Conferring Resistance to Powdery Mildew in Pepper (Capsicum annuum).

Powdery mildew, caused by Leveillula taurica, is a major fungal disease affecting greenhouse-grown pepper (Capsicum annuum). Powdery mildew resistance has a complex mode of inheritance. In the present study, we investigated a novel powdery mildew resistance locus, PMR1, using two mapping populations: 102 'VK515' F2:3 families (derived from a cross between resistant parental line 'VK515R' and susceptible parental line 'VK515S') and 80 'PM Singang' F2 plants (derived from the F1 'PM Singang' commercial hybrid). Genetic analysis of the F2:3 'VK515' and F2 'PM Singang' populations revealed a single dominant locus for inheritance of the powdery mildew resistance trait. Genetic mapping showed that the PMR1 locus is located on syntenic regions of pepper chromosome 4 in a 4-Mb region between markers CZ2_11628 and HRM4.1.6 in 'VK515R'. Six molecular markers including one SCAR marker and five SNP markers were localized to a region 0 cM from the PMR1 locus. Two putative nucleotide-binding site leucine-rich repeat (NBS-LRR)-type disease resistance genes were identified in this PMR1 region. Genotyping-by-sequencing (GBS) and genetic mapping analysis revealed suppressed recombination in the PMR1 region, perhaps due to alien introgression. In addition, a comparison of species-specific InDel markers as well as GBS-derived SNP markers indicated that C. baccatum represents a possible source of such alien introgression of powdery mildew resistance into 'VK515R'. The molecular markers developed in this study will be especially helpful for marker-assisted selection in pepper breeding programs for powdery mildew resistance.

New reference genome sequences of hot pepper reveal the massive evolution of plant disease-resistance genes by retroduplication.

BACKGROUND: Transposable elements are major evolutionary forces which can cause new genome structure and species diversification. The role of transposable elements in the expansion of nucleotide-binding and leucine-rich-repeat proteins (NLRs), the major disease-resistance gene families, has been unexplored in plants. RESULTS: We report two high-quality de novo genomes (Capsicum baccatum and C. chinense) and an improved reference genome (C. annuum) for peppers. Dynamic genome rearrangements involving translocations among chromosomes 3, 5, and 9 were detected in comparison between C. baccatum and the two other peppers. The amplification of athila LTR-retrotransposons, members of the gypsy superfamily, led to genome expansion in C. baccatum. In-depth genome-wide comparison of genes and repeats unveiled that the copy numbers of NLRs were greatly increased by LTR-retrotransposon-mediated retroduplication. Moreover, retroduplicated NLRs are abundant across the angiosperms and, in most cases, are lineage-specific. CONCLUSIONS: Our study reveals that retroduplication has played key roles for the massive emergence of NLR genes including functional disease-resistance genes in pepper plants.

The Korea Nurses' Health Study: A Prospective Cohort Study.

BACKGROUND: The Korea Nurses' Health Study (KNHS) is a prospective cohort study of female nurses, focusing on the effects of occupational, environmental, and lifestyle risk factors on the health of Korean women. MATERIALS AND METHODS: Female registered nurses aged 20-45 years and living in the Republic of Korea were invited to join the study, which began in July 2013. They were asked to complete a web-based baseline survey. The study protocols and questionnaires related to the KNHS are based on the Nurses' Health Study 3 (NHS3) in the United States, although they were modified to reflect the Korean lifestyle. Participants were asked about demographic, lifestyle factors, disease history, occupational exposure, reproductive factors, and dietary habits during their adolescence: Follow-up questionnaires were/will be completed at 6-8 month intervals after the baseline survey. If a participant became pregnant, she answered additional questionnaires containing pregnancy-related information. RESULTS: Among 157,569 eligible female nurses, 20,613 (13.1%) completed the web-based baseline questionnaire. The mean age of the participants was 29.4 ± 5.9 years, and more than half of them were in their 20s. Eighty-eight percent of the participants had worked night shifts as a nurse (mean, 5.3 ± 4.3 nights per month). Approximately 80% of the participants had a body mass index below 23 kg/m2. Gastrointestinal diseases were the most prevalent health issues (25.9%). CONCLUSIONS: The findings from this prospective cohort study will help to identify the effects of lifestyle-related and occupational factors on reproductive health and development of chronic diseases in Korean women.

The Association of Family History of Premature Cardiovascular Disease or Diabetes Mellitus on the Occurrence of Gestational Hypertensive Disease and Diabetes.

BACKGROUND: Gestational hypertensive diseases (GHD) and gestational diabetes mellitus (GDM) increase the risk of cardiovascular disease (CVD) later in life. However, the association between gestational medical diseases and familial history of CVD has not been investigated to date. In the present study, we examined the association between familial history of CVD and GHD or GDM via reliable questionnaires in a large cohort of registered nurses. METHODS: The Korean Nurses' Survey was conducted through a web-based computer-assisted self-interview, which was developed through consultation with cardiologists, gynecologists, and statisticians. We enrolled a total of 9,989 female registered nurses who reliably answered the questionnaires including family history of premature CVD (FHpCVD), hypertension (FHH), and diabetes mellitus (FHDM) based on their medical knowledge. Either multivariable logistic regression analysis or generalized estimation equation was used to clarify the effect of positive family histories on GHD and GDM in subjects or at each repeated pregnancy in an individual. RESULTS: In this survey, 3,695 subjects had at least 1 pregnancy and 8,783 cumulative pregnancies. Among them, 247 interviewees (6.3%) experienced GHD and 120 (3.1%) experienced GDM. In a multivariable analysis adjusted for age, obstetric, and gynecologic variables, age at the first pregnancy over 35 years (adjusted OR 1.61, 95% CI 1.02-2.43) and FHpCVD (adjusted OR 1.60, 95% CI 1.16-2.22) were risk factors for GHD in individuals, whereas FHH was not. FHDM and history of infertility therapy were risk factors for GDM in individuals (adjusted OR 2.68, 95% CI 1.86-3.86; 1.84, 95% CI 1.05-3.23, respectively). In any repeated pregnancies in an individual, age at the current pregnancy and at the first pregnancy, and FHpCVD were risk factors for GHD, while age at the current pregnancy, history of infertility therapy, and FHDM were risk factors for GDM. CONCLUSIONS: The FHpCVD and FHDM are significantly associated with GHD and GDM, respectively. Meticulous family histories should be obtained, and women with family histories of these conditions should be carefully monitored during pregnancy.