Advances in isolated phages that affect Ralstonia solanacearum and their application in the biocontrol of bacterial wilt in plants.

Bacterial wilt is a widespread and devastating disease that impacts the production of numerous crucial crops worldwide. The main causative agent of the disease is Ralstonia solanacearum. Due to the pathogen's broad host range and prolonged survival in the soil, it is challenging to control the disease with conventional strategies. Therefore, it is of great importance to develop effective alternative disease control strategies. In recent years, phage therapy has emerged as an environmentally friendly and sustainable biocontrol alternative, demonstrating significant potential in controlling this severe disease. This paper summarized basic information about isolated phages that infect R. solanacearum, and presented some examples of their application in the biocontrol of bacterial wilt. The risks of phage application and future prospect in this area were also discussed. Overall, R. solanacearum phages have been isolated from various regions and environments worldwide. These phages belong mainly to the Inoviridae, Autographiviridae, Peduoviridae, and Cystoviridae families, with some being unclassified. Studies on the application of these phages have demonstrated their ability to reduce pathogenicity of R. solanacearum through direct lysis or indirect alteration of the pathogen's physiological properties. These findings suggested bacteriophage is a promising tool for biocontrol of bacterial wilt in plants.

Data analysis of physical recovery and injury prevention in sports teaching based on wearable devices.

Athletes can also cause damage to some parts of their body during training, so specialized preparation activities should be carried out before athlete training to reduce the damage caused to the athlete's body, allowing the stressed parts to move and distribute the load. Excessive recovery has a significant effect on improving the performance level of the athletes studied and preventing sports injuries. This article studies the data analysis of body recovery and injury prevention in physical education teaching based on wearable devices. Real time collection of students' exercise data, including indicators such as exercise volume, heart rate, steps, distance, etc., by wearing wearable devices. By using Internet of Things technology to transmit data to cloud servers, data analysis and mining techniques are used to process the data and study issues related to body recovery and injury prevention. Specifically, this article adopts methods such as time series analysis, machine learning algorithms, and artificial neural networks to analyze the relationship between exercise data and body recovery and injury prevention, providing scientific guidance and support for physical education teaching. This method can monitor students' exercise data in real-time, predict the risk of physical recovery and injury, and provide corresponding prevention and guidance suggestions.

Gestational exposure to perfluoroalkyl substances is associated with placental DNA methylation and birth size.

DNA methylation is one potential mechanism for the effects of gestational exposure to perfluoroalkyl substances (PFASs) on fetal growth. We investigated 180 pregnant women who participated in a cohort study conducted in Tangshan City, Northern China, and determined the concentrations of 11 PFASs and the methylation of two genes related to fetal growth [insulin-like growth factor 2 (IGF2) and nuclear receptor subfamily 3 group C member 1 (NR3C1)] and one surrogate marker for global methylation [long interspersed nuclear element-1 (LINE-1)] in placenta tissue. Multiple linear regression analysis was performed to examine the associations of log transformed PFASs with the DNA methylation and birth size. Weighted quantile sum regression was used to determine the mixture effect of PFASs. After adjusting for potential confounders, perfluorooctane sulfonate (PFOS) was negatively associated with the overall methylation of LINE-1. PFASs mixture was negatively associated with the methylation of all CpG loci of LINE-1 and overall methylation of NR3C1. Perfluorootanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), and the PFASs mixture showed negative associations with head circumference. After stratified by newborns' sex, PFOA, PFNA and the PFASs mixture was negatively associated with overall methylation of LINE-1 only in the male subgroup and the methylation of all CpG loci of LINE-1 was negatively associated with ponderal index only in the female subgroup. The interaction of newborns' sex with PFOS and PFOA on overall methylation of IGF2 was statistically significant and so was the interaction of sex with PFOS on overall methylation of LINE-1. These findings suggested that intrauterine exposure to PFASs affected placental DNA methylation and reduced fetal growth, which might be modified by sex.

Exercise practice by obese university students in the context of covid-19 / Prática de exercícios por universitários obesos no contexto da covid-19 / Práctica de ejercicios por universitarios obesos en el contexto del covid-19

ABSTRACT Introduction: The epidemic of COVID-19 has harmed the study and life of obese college students. While new research has pointed out that sports can improve body posture and alleviate psychological problems related to obesity. Objective: Explore obese college students' motivation to play sports and the effects of physical training during COVID-19. Methods: 100 obese college students were selected for the aerobic exercise intervention. Functional and biological indicators were analyzed before and after the experiment. Results: Body shape index, body fat content index, and sports quality index showed expressive changes. The average waist circumference decreased from 99.389 cm to 91.233 cm, an average loss of 8 cm; the average body fat was reduced from 34.644 kg to 30.492 kg after training, with an average decrease of 4 kg; vital capacity increased from 4,416.465 ml before training to 4968.085 ml after the intervention, with an average increase of 500 ml. Conclusion: It can be observed that aerobic exercise helps obese college students to improve their sports motivation, with positive impacts on mental health. The encouragement of sports and engagement in physical exercise tend to strengthen healthy habits, ensuring a better quality of life for college students. Level of evidence II; Therapeutic studies - investigation of treatment outcomes.

RESUMO Introdução: A epidemia da COVID-19 teve um impacto negativo no estudo e na vida dos estudantes universitários obesos. Novas pesquisas apontaram que o esporte pode melhorar a postura corporal e aliviar problemas psicológicos, incluindo aqueles relacionados à obesidade. Objetivo: Explorar a motivação dos estudantes universitários obesos na prática de esportes e os efeitos do treinamento físico durante a COVID-19. Métodos: 100 estudantes universitários obesos foram selecionados para a intervenção com exercícios aeróbicos. Indicadores funcionais e biológicos foram analisados antes e depois do experimento. Resultados: O índice de forma corporal, índice de conteúdo de gordura corporal e índice de qualidade esportiva apresentaram alterações expressivas. A circunferência média da cintura diminuiu de 99,389 cm para 91,233 cm, com perda média de 8 cm; a gordura corporal média foi reduzida de 34,644 kg para 30,492 kg após o treinamento, com uma diminuição média de 4 kg; a capacidade vital elevou-se de 4.416,465 ml antes do treinamento para 4968,085 ml após a intervenção, com um aumento médio de 500 ml. Conclusão: Pode-se observar que o exercício aeróbico auxilia os estudantes universitários obesos a melhorarem a sua motivação esportiva, com impactos positivos na saúde mental. O estimulo ao esporte e o engajamento pelo exercício físico tendem a fortalecer os hábitos saudáveis garantindo uma melhor qualidade de vida aos universitários. Nível de evidência II; Estudos terapêuticos - investigação dos resultados do tratamento.

Resumen Introducción: La epidemia de COVID-19 ha tenido un impacto negativo en el estudio y la vida de los universitarios obesos. Nuevas investigaciones han señalado que el deporte puede mejorar la postura corporal y aliviar problemas psicológicos, incluidos los relacionados con la obesidad. Objetivo: Explorar la motivación de los estudiantes universitarios obesos para practicar deporte y los efectos del entrenamiento físico durante el COVID-19. Métodos: Se seleccionaron 100 estudiantes universitarios obesos para una intervención de ejercicio aeróbico. Se analizaron indicadores funcionales y biológicos antes y después del experimento. Resultados: El índice de forma corporal, el índice de contenido de grasa corporal y el índice de calidad deportiva mostraron cambios expresivos. El perímetro medio de la cintura disminuyó de 99,389 cm a 91,233 cm, con una pérdida media de 8 cm; la grasa corporal media se redujo de 34,644 kg a 30,492 kg tras el entrenamiento, con una disminución media de 4 kg; la capacidad vital aumentó de 4.416,465 ml antes del entrenamiento a 4.968,085 ml después de la intervención, con un aumento medio de 500 ml. Conclusión: Se puede observar que el ejercicio aeróbico ayuda a los estudiantes universitarios obesos a mejorar su motivación deportiva, con repercusiones positivas en la salud mental. La estimulación del deporte y el compromiso con el ejercicio físico tienden a reforzar los hábitos saludables garantizando una mejor calidad de vida a los estudiantes universitarios. Nivel de evidencia II; Estudios terapéuticos - investigación de los resultados del tratamiento.

Exposure to perfluoroalkyl substances was associated with estrogen homeostasis in pregnant women.

Previous studies have suggested that perfluoroalkyl substances (PFASs) can act as endocrine disruptors, but few studies have investigated the effects of serum PFASs on estrogen homeostasis during pregnancy. The present study included 557 pregnant women in Tangshan City, North China, and determined 11 serum PFASs in the early term of pregnancy and three typical estrogens (estrone (E1), estradiol (E2) and estriol (E3)) in the early (n = 557), middle (n = 339), and late (n = 286) terms of pregnancy. Sociodemographic factors and diet information were obtained by structured questionnaires. After adjusting for potential confounders, multiple linear regression model demonstrated negative associations of natural logarithmic transformed serum perfluoroundecanoic acid (Ln PFUdA) with Ln E1and Ln E3 in the early term of pregnancy with ß coefficients of -0.060 (95% confidence interval (CI): -0.101 to -0.019) and -0.041 (95% CI: -0.070 to -0.011), respectively. Ln perfluorodecanoic acid (PFDA) was negatively associated with averaged E1 in the early and middle (EM) terms of pregnancy with a ß coefficient of -0.205 (95% CI: -0.357 to -0.053). Ln perfluorononanoic acid (PFNA) tended to be negatively associated with E2 in the late term of pregnancy with a ß coefficient of -0.134 (95% CI: -0.253 to -0.016) although p-value was slightly greater than 0.05 after false discovery rate (FDR) correction. Mixed effect model found that serum PFDA was negatively associated with E1 (ß = -0.123, 95% CI: -0.235 to -0.012) during the entire pregnancy. These findings suggested that exposure to PFASs disturbed estrogen homeostasis in pregnant women and the effects varied with the terms of pregnancy.

Serum perfluoroalkyl substances in relation to lipid metabolism in Chinese pregnant women.

Laboratory and epidemiologic studies suggested that exposure to perfluoroalkyl substances (PFASs) could affect lipid metabolisms, but data remain limited for pregnant women. A total of 436 pregnant women were selected in Tangshan City, North China. Serum levels of 11 PFASs were determined in the early term of pregnancy. Four lipids (total cholesterol (TC), triglyceride (TG), high-density lipoprotein (HDL), and low-density lipoprotein (LDL)) were measured in the late term of pregnancy. Of 11 PFASs, seven had a detection rate of greater than 70%. After adjusting for potential confounders, natural log-transformed perfluororohexanesulfonic acid (ln PFHxS) was positively associated with TC (ß: 0.184, 95% CI: 0.045-0.321), HDL (ß: 0.040, 95% CI: 0.001-0.083), and LDL (ß: 0.091, 95% CI: 0.001-0.185). Ln perfluoroundecanoic acid (PFUdA) was positively associated with HDL (ß: 0.021, 95% CI: 0.001-0.044), while Ln perfluorodecanoic acid (PFDA) was negatively associated with LDL (ß: -0.053, 95% CI: -0.098∼-0.009) and ln perfluorootanoic acid (PFOA) was negatively associated with LDL/HDL (ß: -0.042, 95% CI: -0.075∼-0.009). In principal component analysis, the component with a large loading of 31.3% for PFOA, perfluorononanoic acid (PFNA), PFDA and PFUdA showed a negative association with LDL/HDL. After serum concentrations of PFASs were categorized into quartiles, a higher level of TC was seen in the second quartile of PFOA or PFNA than the first quartile, but a lower LDL/HDL ratio was seen in the fourth quartile of PFOA, PFUdA or PFDA. These results suggested that exposure to PFASs has a potential to influence lipid metabolisms in pregnant women.

Serum Bisphenol A, glucose homeostasis, and gestational diabetes mellitus in Chinese pregnant women: a prospective study.

Lab studies have suggested that exposure to Bisphenol A (BPA) could disturb glucose homeostasis, but epidemiologic studies are limited and show inconsistent results for pregnant women. For this, 535 pregnant women were selected from a pregnant women cohort established in Tangshan City in North China between 2013 and 2014. Serum concentrations of BPA were measured in the early term of pregnancy, and fasting glucose and insulin levels were repeatedly measured in each of three terms of pregnancy (early, middle, and late). Gestational diabetes mellitus (GDM) were examined by Oral Glucose Tolerance Test (OGTT) in the middle and late terms of pregnancy. BPA was detected in 97.5% of pregnant women with a median of 6.50 ng/ml. Natural log-transformed BPA (Ln BPA) was positively associated with fasting glucose level (ß (95% CI): 0.038 (0.015~0.061)), fasting insulin level (0.195 (0.069~0.321)), and homeostasis model insulin resistance index (HOMA-IR) (0.226 (0.087~0.364)) in the middle term of pregnancy by multiple linear regression model after adjusting for potential confounders. After serum BPA levels were divided into three groups (low, middle, and high), BPA showed a positive dose-response relationship with blood glucose, insulin, and HOMA-IR in the middle term of pregnancy. Increased BPA concentration tended to increase the RR of GDM although not statistically significant (risk ratio: 2.51 (95% CI: 0.68~9.30) for high vs low tertile of BPA concentrations). These findings suggested that exposure to BPA might affect glucose homeostasis and the middle term of pregnancy was a potentially sensitive period.

Comparative transcriptomic analysis reveals that multiple hormone signal transduction and carbohydrate metabolic pathways are affected by Bacillus cereus in Nicotiana tabacum.

Bacillus cereus is thought to be a beneficial bacterium for plants in several aspects, such as promoting plant growth and inducing plant disease resistance. However, there is no detailed report on the effect of Bacillus cereus acting on Nicotiana tabacum. In the present study, RNA-based sequencing (RNA-seq) was used to identify the molecular mechanisms of the interaction between B. cereus CGMCC 5977 and N. tabacum. A total of 7345 and 5604 differentially expressed genes (DEGs) were identified from leaves inoculated with Bacillus cereus at 6 and 24 hpi, respectively. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses revealed that the most DEGs could be significantly enriched in hormone signal transduction, the MAPK signaling pathway, photosynthesis, oxidative stress, and amino sugar, and nucleotide sugar metabolism. Furthermore, glycolysis/gluconeogenesis was severely affected by inoculation with Bacillus cereus. In the hormone signal pathway, multiple DEGs were involved in plant defense-related major hormones, including activation of jasmonic acid (JA), salicylic acid (SA), and ethylene (Eth). Further analyses showed that other hormone-related genes involved in abscisic acid (ABA), gibberellin (GA), auxin (AUX), and cytokinin (CK) also showed changes. Notably, a large number of genes associated with glycolysis/gluconeogenesis, catabolism of starch and oxidative stress were induced. In addition, the majority of DEGs related to nucleic acid sugar metabolism were also significantly upregulated. Biochemical assays showed that the starch content of B. cereus-treated leaves was reduced to 2.51 mg/g and 2.38 mg/g at 6 and 24 hpi, respectively, while that of the control sample was 5.42 mg/g. Overall, our results demonstrated that multiple hormone signal transduction and carbohydrate metabolic pathways are involved in the interaction of tobacco and B. cereus.

Serum phytosterols associate with T helper 1 cytokine concentration in pregnant women.

The dietary phytosterols have been demonstrated to modulate CD4+ T-cell polarization in cells, animals, and humans. However, T helper (Th)1/Th2 dichotomy has rarely been correlated with phytosterols during pregnancy. The present study investigated associations between the serum cytokines and serum phytosterols in 100 pregnant women at 34- to 37-week gestation and their offspring. The results showed that serum concentrations of interferon (IFN)-γ, tumor necrosis factor (TNF)-α, and total Th1 cytokines were positively associated with serum ß-sitosterol level, adjusting for age, BMI, and serum cholesterol. Serum IFN-γ and total Th1 cytokine concentrations positively correlated with total phytosterol concentration, controlling age, BMI, and serum cholesterol. Moreover, none of the cytokines measured correlated with phytosterol concentration in the newborns. Our results show that serum Th1 cytokine concentrations, but not Th2 levels, are positively associated with serum phytosterols in pregnant women. These findings implicate that phytosterols modulate Th1/Th2 balance by inducing Th1 secretions in pregnant women.

PFOS, PFOA, estrogen homeostasis, and birth size in Chinese infants.

Laboratory studies have suggested that perfluoroalkyl substances (PFASs) could affect fetal growth by disrupting estrogen homeostasis, but there are limited data for human. For this, 424 mother-infant pairs were selected from a cohort established in Hebei Province of North China in 2013. Two typical PFASs, perfluorooctyl sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), and three typical estrogens, estrone (E1), ß-estradiol (E2), and estriol (E3), were measured in cord serum. After adjusted for important covariates, serum PFOS was positively related to E1 and E3, but negatively related to E2. Serum PFOA was positively related to serum E1 and negatively related to head circumference at birth. Serum E2 was negatively related to head circumference, body weight, and body length at birth and serum E3 was positively related to body weight. Serum E3 mediated the relationship between serum PFOS and body weight. There were sex-specific differences for the associations between PFOS/PFOA and estrogens/birth size. These findings suggested that exposure to PFASs could affect estrogen homeostasis and fetal growth during pregnancy and that estrogens might mediate the association between exposure to PFASs and fetal growth.

Factors associated with exposure of pregnant women to perfluoroalkyl acids in North China and health risk assessment.

Perfluoroalkyl acids (PFAAs) have been frequently found in blood of pregnant women, but the predictors and potential health risk have not been well studied in China. We recruited 534 pregnant women in Tangshan City of Hebei Province in North China between 2013 and 2014 and measured five PFAAs in serum during their early term of pregnancy, including perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorohexane sulfonic acid (PFHxS), perfluoro­n­undecanoic acid (PFUdA), and perfluorononanoic acid (PFNA). We explored the factors associated with the levels of serum PFAAs and assessed associated health risks. Food consumption information was obtained by food frequency questionnaire covering 100 items. Multiple linear regression model was used to determine the associations of sociodemographic, anthropometric, and food factors with the concentrations of serum PFAAs. Some PFAAs in serum were positively associated with age and body mass index (BMI). Consumption of beans, aquatic products, and eggs was positively associated with the concentrations of several PFAAs after adjusting for important covariates. Pregnant women who ate more cereal, vegetables, mushrooms and alga tended to have lower levels of serum PFOA, PFOS and PFNA. The Hazard index (HI) for reproductive toxicity and developmental toxicity was below 0.8, and the HI for hepatotoxicity beyond 1 was found in 0.37% of pregnant women. These results suggested that age, BMI, and some food consumption were predictors for the exposure to PFAAs in Chinese pregnant women. More attention should be paid to the hepatotoxicity for these exposures.

Perfluoroalkyl substances, glucose homeostasis, and gestational diabetes mellitus in Chinese pregnant women: A repeat measurement-based prospective study.

BACKGROUND: Exposure to perfluoroalkyl substances (PFASs) can affect glucose homeostasis and has been suggested as a potential risk of diabetes mellitus, but data are limited for pregnant women. OBJECTIVES: We aimed to explore the associations of exposure to PFASs with glucose homeostasis and gestational diabetes mellitus (GDM) in Chinese pregnant women. METHODS: The current study was conducted in Hebei Province of Northern China between 2013 and 2014 and 560 pregnant women were recruited in their early term of pregnancy and two representative serum PFASs, perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS), were measured. In 385 pregnant women who completed oral glucose tolerance test (OGTT), the associations of serum PFOA and PFOS concentrations with fasting blood glucose (FBG), fasting insulin (FIns), and homeostasis model assessment of insulin resistance (HOMA-IR) in the early, middle, and late terms of pregnancy and occurrence of GDM were examined using linear and Cox proportional hazard regression models. The reproducibility of serum PFASs during pregnancy was assessed in 230 pregnant women. RESULTS: The intraclass correlation coefficients of serum PFASs, covariates, and outcomes based on averaged repeat measurement (0.35-0.96) were higher than those based on single measurement (0.16-0.92). Serum PFOA was positively associated with averaged FIns and HOMA-IR in the early, middle, and late terms of pregnancy and averaged blood glucose level at 1 h and 2 h of OGTT, but serum PFOS tended to be negatively associated with averaged FBG and OGTT blood glucose. The adjusted hazard ratios of GDM associated with serum PFOA and PFOS were 1.98 (95% confidence interval: 0.70-5.57; p-value: 0.197) and 0.71 (0.29-1.75; 0.453), respectively. CONCLUSIONS: Our data raised a possibility that exposure to PFASs might have different influences on glucose homeostasis and GDM in Chinese pregnant women. More lab and human studies are needed to further test the hypothesis and investigate potential mechanisms.

[Correlation between the expression level of coiled-coil domain-containing protein 80 and obesity].

OBJECTIVE: To explore the relationship between expression of coiled-coil domain-containing protein 80(CCDC80) and obesity in serum and adipose tissues. METHODS: A cross-sectional survey was conducted in a hospital in Tangshan in September 2010. 100 people including 78 healthy people and 22 with type-2 diabetes were recruited. Another 36 female patients with benign tumor of Obstetrics and Gynecology were also recruited. Demographic characteristics and serum samples were collected from all subjects, basic biochemical indicators were tested. All subjects were divided into 'Normal Weight' and 'Overweight and Obese' according to their BMI (BMI <24.0 kg/m(2); BMI≥24 kg/m(2)). Serum CCDC80 of the 100 subjects was detected by ELISA. Visceral and subcutaneous fat were derived from the other 36 female subjects, and Real-time PCR was used to detect CCDC80 mRNA expression in adipose tissues. Pearson correlation and multiple linear regression were used to analyze the correlation between serum or adipose CCDC80 expression and waist, BMI, and other biochemical indicators. RESULTS: The age of 100 subjects was (52.9±8.4) years old. 44% of them were women (44 cases) and 56% of them were men (56 cases). After dividing them into three groups according to their BMI, covariance analysis were conducted, and age and gender were adjusted. The HDL-C level was significantly different among three groups (F = 10.73, P < 0.001): 'Overweight and obese combined with diabetes' group ((0.90±0.06) mmol/L)< 'Overweight and obese' group ((1.14±0.04) mmol/L) < 'Normal weight' group ((1.28±0.05) mmol/L). The adjusted expression of serum CCDC80 of the 100 subjects was (5.84±0.16) pg/ml, (5.81±0.98) pg/ml among men and (5.97±0.89) pg/ml among women, and there was no significant difference (t = -0.812, P = 0.419) between genders. ANOVA revealed that there was no significant differences of the expression of serum CCDC80 among three groups (F = 1.06, P = 0.351), 'Normal weight' group was (5.84±0.16) pg/ml, 'overweight and obese' group was (6.11±0.14) pg/ml, and 'Overweight and obese combined with diabetes' group was (5.84±0.19) pg/ml. The analysis showed that FBG had a negative correlation with serum CCDC80 (R(b) = -0.223, P = 0.026). Multivariate linear regression had a similar result, with 1 mmol/L increase of serum FBG, serum CCDC80 decreases for 0.24 pg/ml (ß = -0.24, 95% CI: -0.21--0.02). There was also a negative correlation between serum CCDC80 and FBG in overweight and obese people (R(a) = -0.368, P = 0.013). Besides, CCDC80 mRNA was detected in both subcutaneous and visceral adipose tissue of 36 cases, the expression level was 0.06±0.02 for subcutaneous fat, was 0.05±0.04 for visceral fat, and the expression in visceral fat was lower (0.05±0.03) than that in subcutaneous fat (0.06±0.03) (t = 2.50, P = 0.025) among overweight and obese group. There was a negative correlation between waist and visceral CCDC80 mRNA expression (r = -0.472, P = 0.035). CONCLUSION: This study suggested that CCDC80 may be involved in energy and insulin metabolism, and plays a protective role in obesity and diabetes.

A killer-protector system regulates both hybrid sterility and segregation distortion in rice.

Hybrid sterility is a major form of postzygotic reproductive isolation that restricts gene flow between populations. Cultivated rice (Oryza sativa L.) consists of two subspecies, indica and japonica; inter-subspecific hybrids are usually sterile. We show that a killer-protector system at the S5 locus encoded by three tightly linked genes [Open Reading Frame 3 (ORF3) to ORF5] regulates fertility in indica-japonica hybrids. During female sporogenesis, the action of ORF5+ (killer) and ORF4+ (partner) causes endoplasmic reticulum (ER) stress. ORF3+ (protector) prevents ER stress and produces normal gametes, but ORF3- cannot prevent ER stress, resulting in premature programmed cell death and leads to embryo-sac abortion. Preferential transmission of ORF3+ gametes results in segregation distortion in the progeny. These results add to our understanding of differences between indica and japonica rice and may aid in rice genetic improvement.

Complex evolution of S5, a major reproductive barrier regulator, in the cultivated rice Oryza sativa and its wild relatives.

• The hybrid sterility gene S5 comprises three types of alleles in cultivated rice. Such tri-allelic system provided a unique opportunity to study the molecular bases of evolutionary changes underlying reproductive isolation in plants. • We analysed the sequence diversity and evolutionary history of S5 in 138 Oryza accessions. We also examined the effect of the two functional variations (C819A and C1412T) in determining hybrid sterility by transformation. • Nineteen haplotypes were identified, which were classified into the indica-like, the japonica-like and the wide-compatibility gene (WCG)-like group, according to the sequence features of the tri-allelic system. The origin and evolutionary course of the three allelic groups were investigated, thus confirming the independent origins of indica and japonica subspecies. There were perfect associations between C819A and C1412T in the rice germplasm assayed, and the combination of C819 and C1412 was required for hybrid sterility. Evidence of positive selection in the WCG-like alleles suggested that they might have been favored by selection for higher compatibility in hybrids. • The complex evolution of S5 revealed the counteractive function of the three allelic groups at the species level. S5 might perform an important primary function in an evolutionary scale, and hybrid sterility acts as a 'byproduct' of this speciation gene.

A triallelic system of S5 is a major regulator of the reproductive barrier and compatibility of indica-japonica hybrids in rice.

Hybrid sterility is a major form of postzygotic reproductive isolation. Although reproductive isolation has been a key issue in evolutionary biology for many decades in a wide range of organisms, only very recently a few genes for reproductive isolation were identified. The Asian cultivated rice (Oryza sativa L.) is divided into two subspecies, indica and japonica. Hybrids between indica and japonica varieties are usually highly sterile. A special group of rice germplasm, referred to as wide-compatibility varieties, is able to produce highly fertile hybrids when crossed to both indica and japonica. In this study, we cloned S5, a major locus for indica-japonica hybrid sterility and wide compatibility, using a map-based cloning approach. We show that S5 encodes an aspartic protease conditioning embryo-sac fertility. The indica (S5-i) and japonica (S5-j) alleles differ by two nucleotides. The wide compatibility gene (S5-n) has a large deletion in the N terminus of the predicted S5 protein, causing subcellular mislocalization of the protein, and thus is presumably nonfunctional. This triallelic system has a profound implication in the evolution and artificial breeding of cultivated rice. Genetic differentiation between indica and japonica would have been enforced because of the reproductive barrier caused by S5-i and S5-j, and species coherence would have been maintained by gene flow enabled by the wide compatibility gene.