Sexual Reproduction Research Articles

The ING protein Fng2 associated with RPD3 HDAC complex for the regulation of fungal development and pathogenesis in wheat head blight fungus

ING proteins display a high level of evolutionary conservation across various species, and play a crucial role in modulating histone acetylation levels, thus regulating various important biological processes in yeast and humans. Filamentous fungi possess distinct biological characteristics that differentiate them from yeasts and humans, and the specific roles of ING proteins in filamentous fungi remain largely unexplored. In this study, an ING protein, Fng2, orthologous to the yeast Pho23, has been identified in the wheat head blight fungus Fusarium graminearum. The deletion of the FNG2 gene resulted in defects in vegetative growth, conidiation, sexual reproduction, plant infection, and deoxynivalenol (DON) biosynthesis. Acting as a global regulator, Fng2 exerts negative control over histone H4 acetylation and governs the expression of over 4000 genes. Moreover, almost half of the differentially expressed genes in the fng3 mutant were found to be co-regulated by Fng2, emphasizing the functional association between these two ING proteins. Notably, the fng2 fng3 double mutant exhibits significantly increased H4 acetylation and severe defects in both fungal development and pathogenesis. Furthermore, Fng2 localizes within the nucleus and associates with the FgRpd3 histone deacetylase (HDAC) to modulate gene expression. Overall, Fng2's interaction with FgRpd3, along with its functional association with Fng3, underscores its crucial involvement in governing gene expression, thereby significantly influencing fungal growth, asexual and sexual development, pathogenicity, and secondary metabolism.

Exploration of Genome-Wide Recombination Rate Variation Patterns at Different Scales in Pigs.

Meiotic recombination is a prevalent process in eukaryotic sexual reproduction organisms that plays key roles in genetic diversity, breed selection, and species evolution. However, the recombination events differ across breeds and even within breeds. In this study, we initially computed large-scale population recombination rates of both sexes using approximately 52 K SNP genotypes in a total of 3279 pigs from four different Chinese and Western breeds. We then constructed a high-resolution historical recombination map using approximately 16 million SNPs from a sample of unrelated individuals. Comparative analysis of porcine recombination events from different breeds and at different resolutions revealed the following observations: Firstly, the 1Mb-scale pig recombination maps of the same sex are moderately conserved among different breeds, with the similarity of recombination events between Western pigs and Chinese indigenous pigs being lower than within their respective groups. Secondly, we identified 3861 recombination hotspots in the genome and observed medium- to high-level correlation between historical recombination rates (0.542~0.683) and estimates of meiotic recombination rates. Third, we observed that recombination hotspots are significantly far from the transcription start sites of pig genes, and the silico-predicted PRDM9 zinc finger domain DNA recognition motif is significantly enriched in the regions of recombination hotspots compared to recombination coldspots, highlighting the potential role of PRDM9 in regulating recombination hotspots in pigs. Our study analyzed the variation patterns of the pig recombination map at broad and fine scales, providing a valuable reference for genomic selection breeding and laying a crucial foundation for further understanding the molecular mechanisms of pig genome recombination.

Deep learning insights into the architecture of the mammalian egg-sperm fusion synapse

A crucial event in sexual reproduction is when haploid sperm and egg fuse to form a new diploid organism at fertilization. In mammals, direct interaction between egg JUNO and sperm IZUMO1 mediates gamete membrane adhesion, yet their role in fusion remains enigmatic. We used AlphaFold to predict the structure of other extracellular proteins essential for fertilization to determine if they could form a complex that may mediate fusion. We first identified TMEM81, whose gene is expressed by mouse and human spermatids, as a protein having structural homologies with both IZUMO1 and another sperm molecule essential for gamete fusion, SPACA6. Using a set of proteins known to be important for fertilization and TMEM81, we then systematically searched for predicted binary interactions using an unguided approach and identified a pentameric complex involving sperm IZUMO1, SPACA6, TMEM81 and egg JUNO, CD9. This complex is structurally consistent with both the expected topology on opposing gamete membranes and the location of predicted N-glycans not modeled by AlphaFold-Multimer, suggesting that its components could organize into a synapse-like assembly at the point of fusion. Finally, the structural modeling approach described here could be more generally useful to gain insights into transient protein complexes difficult to detect experimentally.

Deep learning insights into the architecture of the mammalian egg-sperm fusion synapse.

A crucial event in sexual reproduction is when haploid sperm and egg fuse to form a new diploid organism at fertilization. In mammals, direct interaction between egg JUNO and sperm IZUMO1 mediates gamete membrane adhesion, yet their role in fusion remains enigmatic. We used AlphaFold to predict the structure of other extracellular proteins essential for fertilization to determine if they could form a complex that may mediate fusion. We first identified TMEM81, whose gene is expressed by mouse and human spermatids, as a protein having structural homologies with both IZUMO1 and another sperm molecule essential for gamete fusion, SPACA6. Using a set of proteins known to be important for fertilization and TMEM81, we then systematically searched for predicted binary interactions using an unguided approach and identified a pentameric complex involving sperm IZUMO1, SPACA6, TMEM81 and egg JUNO, CD9. This complex is structurally consistent with both the expected topology on opposing gamete membranes and the location of predicted N-glycans not modeled by AlphaFold-Multimer, suggesting that its components could organize into a synapse-like assembly at the point of fusion. Finally, the structural modeling approach described here could be more generally useful to gain insights into transient protein complexes difficult to detect experimentally.

Unveiling elevated spontaneous mutation rates in Phyllostachys edulis (Moso Bamboo) through whole genome sequencing (WGS) and investigating the impact of atmospheric and room temperature plasma (ARTP) induced mutagenesis

Moso bamboo, recognized for its wide distribution and economic importance, encounters challenges in varietal enhancement owing to its protracted sexual reproduction cycle. This study employed whole-genome resequencing to identify spontaneous mutations in Moso bamboo and investigated mutagenesis using atmospheric and room temperature plasma (ARTP). Through the sequencing results, we identified a population of flowering bamboo as an asexual breeding line. Notably, the flowering Moso bamboo population, exclusively derived from asexual reproduction, exhibited a high spontaneous mutation rate (4.54 × 10−4 to 1.15 × 10−3/bp) during sexual reproduction, considering parental and cross-pollination effects. Genetic disparities between the offspring and parents exhibited a bimodal distribution, indicating a substantial cross-pollination rate. ARTP mutagenesis increased structural variations in offspring, whereas changes in SNPs and INDELs were less pronounced. Sanger sequencing validated the gene subset, providing a foundation for the investigation of spontaneous mutation rates via whole-genome sequencing. These insights, particularly from mutagenized offspring sequencing, can contribute to Moso bamboo breeding strategies.

Termite females prefer hybrid mating to parthenogenesis when conspecific males are absent

Abstract Parthenogenesis and interspecific mating are alternative reproductive strategies that species have evolved alternative strategies when the opportunity of sexual reproduction is hindered by the natural environment. However, it is still unclear how to make a choice between parthenogenesis and interspecific mating when females are unable to reproduce sexually with males of the same species. This study mainly investigated the reproductive behaviour of female termites in the absence of male termites of the same species. Here, reproductive behaviours of females Reticulitermes aculabialis (Ra♀) were observed when they encountered a male R. flaviceps (Rf♂) with the absence of male R. aculabialis(Ra♂). The results showed that Ra♀‐Rf♂ tandems were more prevalent and stable compared to Ra♀‐Ra♀ tandems. When a tandem inadvertently broke apart, the female R. aculabialis displayed longer pauses while waiting for male R. flaviceps, but shorter pauses when another female R. aculabialis was involved. Furthermore, there were mating behaviour between female R. aculabialis and males R. flaviceps, resulting in offspring produced in paired Ra♀‐Rf♂ colonies were hybridization between female R. aculabialis and male R. flaviceps. These results suggest that interspecific mating and recombination is an important aspect for the choice of reproduction strategy, which will provide new insights into the trade‐off between gene contribution rate and genetic diversity.

Secondary-tail formation during stolonization in the Japanese green syllid, Megasyllis nipponica.

Benthic annelids belonging to the family Syllidae show a distinctive sexual reproduction mode called "stolonization," in which posterior segments are transformed into a reproductive individual-like unit called a "stolon." Megasyllis nipponica forms a stolon head and a secondary tail in the middle of the trunk before a stolon detaches, while, in the case of posterior amputation, posterior regeneration initiates at the wound after amputation. To understand the difference between posterior regeneration and secondary-tail formation during stolonization, detailed comparisons between the developmental processes of these two tail-formation types were performed in this study. Morphological and inner structural observations (i.e., cell proliferation and muscular/nervous development) showed that some processes of posterior regeneration, such as blastema formation and muscular/nervous regeneration at the amputation site, are missing during secondary-tail formation. In contrast, the secondary tail showed some unique features, such as the formation of ventrolateral half-tail buds that later fused in the middle and muscle/nerve branches formed before the detachment of the stolon. These novel features in the process of stolonization are suggested to be adaptive since the animals need to recover a posterior end quickly to stolonize again.

Extending Grime's CSR model to predict plant demographic responses across resource availability gradients: evidence from the patagonian steppes

Sexual reproduction, growth, and survival are crucial demographic strategies for plant population viability. Here, we propose a conceptual model predicting demographic responses of species based on their ecological strategy and the heterogeneity of environmental conditions within a biogeographical unit and then applied it to a case study from a 5˚ latitudinal gradient in the Patagonian steppes. We also aim to disentangle genetic from environmental effects on demographic responses. We performed in situ and common garden experiments with two species from six local populations of the Occidental Phytogeographical District of the Patagonian steppes. Species differ in key ecological traits, and thus fit into Grime's model for evolutionary strategies in plants: one as competitive species and the other as stress‐tolerant species. We calculated population growth rate (λ) and performed elasticity analyses to compare the contribution of each demographic strategy to population fitness between species and among local populations distributed along 600 km latitudinal gradient with differences in mean annual precipitation (MAP). We highlight four results. First, the competitive species change from sexual reproduction to growth as MAP increases. Second, the stress‐tolerant species relied on growth and survival along the MAP gradient. Third, interannual variation in resource availability modulated demographic responses for both strategies. Fourth, based on the comparison of the in situ and common garden experiments, we submit that demographic responses were genetically driven. Our study shows that demographic responses can be roughly predicted by the ecological strategy across environmental gradients. We show that differences arise not only between species, but also were genetically driven differences within species among local populations. Scaling up plant‐level responses to population‐level dynamics allows for a process‐based understanding of current and future biogeographical species organization. Furthermore, conservation and restoration efforts should be guided by demographic strategies underlying population viability.

FgFAD12 Regulates Vegetative Growth, Pathogenicity and Linoleic Acid Biosynthesis in Fusarium graminearum.

Polyunsaturated fatty acids (PUFAs), as important components of lipids, play indispensable roles in the development of all organisms. ∆12 fatty acid desaturase (FAD12) is a speed-determining step in the biosynthesis of PUFAs. Here, we report the characterization of FAD12 in Fusarium graminearum, which is the prevalent agent of Fusarium head blight, a destructive plant disease worldwide. The results demonstrated that deletion of the FgFAD12 gene resulted in defects in vegetative growth, conidial germination and plant pathogenesis but not sexual reproduction. A fatty acid analysis further proved that the deletion of FgFAD12 restrained the reaction of oleic acid to linoleic acid, and a large amount of oleic acid was detected in the cells. Moreover, the ∆Fgfad12 mutant showed increased resistance to osmotic stress and reduced tolerance to oxidative stress. The expression of FgFAD12 did show a temperature-dependent manner, which was not affected at a low temperature of 10 °C when compared to 25 °C. RNA-seq analysis further demonstrated that most genes enriched in fatty acid metabolism, the biosynthesis of unsaturated fatty acids, fatty acid biosynthesis, fatty acid degradation, steroid biosynthesis and fatty acid elongation pathways were significantly up-regulated in the ∆Fgfad12 mutants. Overall, our results indicate that FgFAD12 is essential for linoleic acid biosynthesis and plays an important role in the infection process of F. graminearum.

Fungal holobionts as blueprints for synthetic endosymbiotic systems.

Rhizopus microsporus is an example of a fungal holobiont. Strains of this species can harbor bacterial and viral endosymbionts inherited by the next generation. These microbial allies increase pathogenicity and defense and control asexual and sexual reproduction.

The crane fly glycosylated triketide δ-lactone cornicinine elicits akinete differentiation of the cyanobiont in aquatic Azolla fern symbioses.

The restriction of plant-symbiont dinitrogen fixation by an insect semiochemical had not been previously described. Here we report on a glycosylated triketide δ-lactone from Nephrotoma cornicina crane flies, cornicinine, that causes chlorosis in the floating-fern symbioses from the genus Azolla. Only the glycosylated trans-A form of chemically synthesized cornicinine was active: 500 nM cornicinine in the growth medium turned all cyanobacterial filaments from Nostoc azollae inside the host leaf-cavities into akinetes typically secretingCTB-bacteriocins. Cornicinine further inhibited akinete germination in Azolla sporelings, precluding re-establishment of the symbiosis during sexual reproduction. It did not impact development of the plant Arabidopsis thaliana or several free-living cyanobacteria from the genera Anabaena or Nostoc but affected the fern host without cyanobiont. Fern-host mRNA sequencing from isolated leaf cavities confirmed high NH4-assimilation and proanthocyanidin biosynthesis in this trichome-rich tissue. After cornicinine treatment, it revealed activation of Cullin-RING ubiquitin-ligase-pathways, known to mediate metabolite signaling and plant elicitation consistent with the chlorosis phenotype, and increased JA-oxidase, sulfate transport and exosome formation. The work begins to uncover molecular mechanisms of cyanobiont differentiation in a seed-free plant symbiosis important for wetland ecology or circular crop-production today, that once caused massive CO2 draw-down during the Eocene geological past.

Advances in Understanding Fusarium graminearum: Genes Involved in the Regulation of Sexual Development, Pathogenesis, and Deoxynivalenol Biosynthesis.

The wheat head blight disease caused by Fusarium graminearum is a major concern for food security and the health of both humans and animals. As a pathogenic microorganism, F. graminearum produces virulence factors during infection to increase pathogenicity, including various macromolecular and small molecular compounds. Among these virulence factors, secreted proteins and deoxynivalenol (DON) are important weapons for the expansion and colonization of F. graminearum. Besides the presence of virulence factors, sexual reproduction is also crucial for the infection process of F. graminearum and is indispensable for the emergence and spread of wheat head blight. Over the last ten years, there have been notable breakthroughs in researching the virulence factors and sexual reproduction of F. graminearum. This review aims to analyze the research progress of sexual reproduction, secreted proteins, and DON of F. graminearum, emphasizing the regulation of sexual reproduction and DON synthesis. We also discuss the application of new gene engineering technologies in the prevention and control of wheat head blight.

Wickerhamomyces corioli f.a., sp. nov., a novel yeast species discovered in two mushroom species.

Two yeast strains, designated as 19-39-3 and 19-40-2, obtained from the fruiting bodies of Trametes versicolor and Marasmius siccus collected in Yunwu Mountain Forest Park, PR China, have been identified as representing a novel asexual ascomycetous yeast species. From the results of phylogenetic analyses of the sequences of the D1/D2 domains of the large subunit (LSU) rRNA, small subunit (SSU) rRNA and translation elongation factor 1-α (TEF1) genes, it was determined that these strains represent a member of the genus Wickerhamomyces, with Wickerhamomyces alni and Candida ulmi as the closest relatives. The novel species exhibited 6.6 and 6.7% differences in the D1/D2 domains compared with W. alni and C. ulmi, respectively. Additionally, distinct biochemical and physiological differences were observed between the novel species and its related counterparts. No sexual reproduction was observed in these strains, leading to the proposal of the name Wickerhamomyces corioli f.a., sp. nov. for this newly discovered species.

A cyclical switch of gametogenic pathways in hybrids depends on the ploidy level

The cellular and molecular mechanisms governing sexual reproduction are conserved across eukaryotes. Nevertheless, hybridization can disrupt these mechanisms, leading to asexual reproduction, often accompanied by polyploidy. In this study, we investigate how ploidy level and ratio of parental genomes in hybrids affect their reproductive mode. We analyze the gametogenesis of sexual species and their diploid and triploid hybrids from the freshwater fish family Cobitidae, using newly developed cytogenetic markers. We find that diploid hybrid females possess oogonia and oocytes with original (diploid) and duplicated (tetraploid) ploidy. Diploid oocytes cannot progress beyond pachytene due to aberrant pairing. However, tetraploid oocytes, which emerge after premeiotic genome endoreplication, exhibit normal pairing and result in diploid gametes. Triploid hybrid females possess diploid, triploid, and haploid oogonia and oocytes. Triploid and haploid oocytes cannot progress beyond pachytene checkpoint due to aberrant chromosome pairing, while diploid oocytes have normal pairing in meiosis, resulting in haploid gametes. Diploid oocytes emerge after premeiotic elimination of a single-copied genome. Triploid hybrid males are sterile due to aberrant pairing and the failure of chromosomal segregation during meiotic divisions. Thus, changes in ploidy and genome dosage may lead to cyclical alteration of gametogenic pathways in hybrids.

Toxoplasmosis in animals and humans: a neglected zoonotic disease in Bangladesh.

Toxoplasmosis, caused by Toxoplasma gondii, is a zoonotic disease that affects a wide range of warm-blooded animals, including humans. The parasite undergoes both sexual and asexual reproduction in intermediate hosts (humans and animals) and definitive hosts (cats). Transmission in humans occurs through consuming oocyst-contaminated water, fruits, vegetables, and raw or undercooked meats. In Bangladesh, several factors contribute to an increased risk of contracting toxoplasmosis. The parasite is reported to cause diseases among livestock such as goats and sheep in this country, and it has also been associated with some human illnesses. Toxoplasmosis prevalence varies significantly worldwide, with developing countries like Bangladesh experiencing higher rates. Diagnostic methods include both conventional non-DNA-based tests and molecular detection techniques, while treatment options involve using antiparasitic drugs like sulfadiazine and pyrimethamine. To control toxoplasmosis, essential steps include improving sanitation, promoting safe food handling, and educating the public about risks related to cat ownership and undercooked meat consumption. Implementing prenatal screening and treatment is also important. With the growing popularity of pet ownership in urban areas, it becomes essential to emphasize the veterinary and public health significance of toxoplasmosis in Bangladesh. This article comprehensively reviews various aspects of toxoplasmosis, with a specific focus on the situation in Bangladesh.

Features of the formation of the ontogenetic structure of the cenopopulation and seed productivity of <i>Sanguisorba officinalis</i> in the conditions of forest and forest‐steppe vegetation of the Middle Volga region, Russia

The purpose of this work is to study the features of the life cycle of Sanguisorba officinalis in various types of vegetation in the Republic of Tatarstan, Russia. We used traditional methods for studying the cenopopulation, analysis of the calendar age of plants of various ontogenetic states, and potential and actual seed productivity. Under broad‐leaved forest conditions, a young normal population was formed on the basis of slowly developing plants. In conditions of open communities, young cenopopulations were formed on the basis of intensive seed reproduction processes. The young cenopopulation can be recommended for further study in biomass exploitation. The predominance of long‐lived vegetative and immature plants in the conditions of a broad‐leaved forest is associated with difficulties in the transition of individuals to sexual reproduction. The maintenance of numbers is carried out through vegetative growth and reproduction. With deterioration of ecological and coenotic conditions, above‐ground shoots were not formed but regressive‐quasisenile coenopopulations were formed. Seed productivity was determined by ecological and cenotic conditions. On the steppe meadow of the Bugulma district, the lowest seed productivity index was 9 %. The lowest indicator of the trait “Number of full‐fledged seeds” (the average indicator was 7), low seed germination and germination energy were also noted there. The highest values of these indicators were noted n glades of the broad‐leaved areas of the same region. The realization of the reproductive system of Sanguisorba officinalis even under extreme conditions and the survival of the species in various types of vegetation suggest that the territory of the Republic of Tatarstan is included in the ceno‐area of the species. This will permit the creation of plantations in the republic.

The massive 340 megabase genome of Anisogramma anomala, a biotrophic ascomycete that causes eastern filbert blight of hazelnut

BackgroundThe ascomycete fungus Anisogramma anomala causes Eastern Filbert Blight (EFB) on hazelnut (Corylus spp.) trees. It is a minor disease on its native host, the American hazelnut (C. americana), but is highly destructive on the commercially important European hazelnut (C. avellana). In North America, EFB has historically limited commercial production of hazelnut to west of the Rocky Mountains. A. anomala is an obligately biotrophic fungus that has not been grown in continuous culture, rendering its study challenging. There is a 15-month latency before symptoms appear on infected hazelnut trees, and only a sexual reproductive stage has been observed. Here we report the sequencing, annotation, and characterization of its genome.ResultsThe genome of A. anomala was assembled into 108 scaffolds totaling 342,498,352 nt with a GC content of 34.46%. Scaffold N50 was 33.3 Mb and L50 was 5. Nineteen scaffolds with lengths over 1 Mb constituted 99% of the assembly. Telomere sequences were identified on both ends of two scaffolds and on one end of another 10 scaffolds. Flow cytometry estimated the genome size of A. anomala at 370 Mb. The genome exhibits two-speed evolution, with 93% of the assembly as AT-rich regions (32.9% GC) and the other 7% as GC-rich (57.1% GC). The AT-rich regions consist predominantly of repeats with low gene content, while 90% of predicted protein coding genes were identified in GC-rich regions. Copia-like retrotransposons accounted for more than half of the genome. Evidence of repeat-induced point mutation (RIP) was identified throughout the AT-rich regions, and two copies of the rid gene and one of dim-2, the key genes in the RIP mutation pathway, were identified in the genome. Consistent with its homothallic sexual reproduction cycle, both MAT1-1 and MAT1-2 idiomorphs were found. We identified a large suite of genes likely involved in pathogenicity, including 614 carbohydrate active enzymes, 762 secreted proteins and 165 effectors.ConclusionsThis study reveals the genomic structure, composition, and putative gene function of the important pathogen A. anomala. It provides insight into the molecular basis of the pathogen’s life cycle and a solid foundation for studying EFB.

Applying knowledge and experience from potato (Solanum tuberosum) to update genetic stability data requirements in the risk assessment for vegetatively propagated biotech crops.

Regulatory agencies require data on genetic stability as part of the safety assessment for biotech crops, even though the genetic stability of a plant is not necessarily an environmental, human or animal health safety concern. While sexual reproduction has the potential to introduce genomic variation in conventionally bred and biotech crops, vegetative propagation is genetically stable. In vegetatively propagated crops, meiosis does not occur thus limiting the number of homologous recombination events that could lead to chromosomal rearrangements in progeny plants. Genetic stability data is often, but should not be, an automatic requirement for the safety assessment of vegetatively propagated biotech crops. Genetic stability data from biotech potato events has demonstrated that vegetative propagation of potato tubers does not affect the stability of introduced DNA sequences or lead to loss of trait efficacy. The knowledge and experience gained from over 30years of assessing the safety of biotech crops can be used by regulatory authorities to eliminate data requirements that do not address environmental, food or feed safety concerns. As a first step, regulators should consider removing requirements for genetic stability as part of the safety review for vegetatively propagated biotech crops.

Survey of Phyllosticta citricarpa mating type in the São Paulo citrus belt and optimization of in vitro ascospore production

AbstractPhyllosticta citricarpa, the citrus black spot causal agent, requires both mating types, designated as MAT1‐1 and MAT1‐2, to produce ascospores. Mating‐type ratio in some citrus‐growing areas has been characterized but remains little known in the São Paulo (SP) citrus belt, the largest sweet orange producer worldwide. A protocol for in vitro ascospore production was developed recently; however, there are few studies regarding the optimal conditions for their production. Thus, this study aimed to determine the mating‐type ratio in SP and quantify ascospores produced under different conditions in vitro. The mating types were identified by duplex PCR, and ascospore production was assessed in five culture media: potato dextrose agar (PDA), ½ PDA, malt extract agar (MEA), oatmeal agar (OMA) and citrus agar (CA), and at temperatures from 10 to 30°C. The ratio of MAT1‐1 and MAT1‐2 was similar to 1:1. Ascospore production reached peaks of 8.0, 7.0 and 3.0 × 103 ascospores/mL in MEA, PDA and ½ PDA, respectively. There were no ascospores observed in OMA and CA. P. citricarpa ascospores were observed only at 15, 20 and 25°C in PDA, with peaks of up to 2.0 × 103 ascospores/mL at 42, 35 and 21 days, respectively. There were no ascospores observed at 10 and 30°C. Both mating types are similarly distributed in the SP citrus belt, and in vitro ascospore production may be optimized by using MEA at 25°C. These data provide a better understanding of P. citricarpa sexual reproduction and a background for further studies with ascospores.

DNA methylation remodeling and the functional implication during male gametogenesis in rice

BackgroundEpigenetic marks are reprogrammed during sexual reproduction. In flowering plants, DNA methylation is only partially remodeled in the gametes and the zygote. However, the timing and functional significance of the remodeling during plant gametogenesis remain obscure.ResultsHere we show that DNA methylation remodeling starts after male meiosis in rice, with non-CG methylation, particularly at CHG sites, being first enhanced in the microspore and subsequently decreased in sperm. Functional analysis of rice CHG methyltransferase genes CMT3a and CMT3b indicates that CMT3a functions as the major CHG methyltransferase in rice meiocyte, while CMT3b is responsible for the increase of CHG methylation in microspore. The function of the two histone demethylases JMJ706 and JMJ707 that remove H3K9me2 may contribute to the decreased CHG methylation in sperm. During male gametogenesis CMT3a mainly silences TE and TE-related genes while CMT3b is required for repression of genes encoding factors involved in transcriptional and translational activities. In addition, CMT3b functions to repress zygotic gene expression in egg and participates in establishing the zygotic epigenome upon fertilization.ConclusionCollectively, the results indicate that DNA methylation is dynamically remodeled during male gametogenesis, distinguish the function of CMT3a and CMT3b in sex cells, and underpin the functional significance of DNA methylation remodeling during rice reproduction.