Male Sterility Research Articles

The evolution and maintenance of trioecy with cytoplasmic male sterility.

Trioecy, the co-existence of females, males and hermaphrodites, is a rare sexual system in plants that may be an intermediate state in transitions between hermaphroditism and dioecy. Previous models have identified pollen limitation as a necessary condition for the evolution of trioecy from hermaphroditism. In these models, the seed-production and pollen production of females and males relative to those of hermaphrodites, respectively, are compromised by self-fertilization by hermaphrodites under pollen- limitation. Here, we investigate the evolution of trioecy via the invasion of cytoplasmic male sterility (CMS) into androdioecious populations in which hermaphrodites co-occur with males and where the male determiner is linked to a (partial) fertility restorer. We show that the presence of males in a population renders invasion by CMS more difficult. However, the presence of males also facilitates the maintenance of trioecy even in the absence of pollen limitation by negative frequency-dependent selection, because males reduce the transmission of CMS by females by siring sons (which cannot transmit CMS). We discuss our results in light of empirical observations of trioecy in plants and its potential role in the evolution of dioecy.

Snip, Support, and Shared Stories: Exploring Reddit Users' Experiences With Vasectomy.

Introduction Vasectomy is a common procedure for male sterilization. During pre-procedural counseling,men and their partnersare often concerned with postoperative pain or sexual dysfunction. Research examining internet forums to explore these concernsis limited.In this study, we selected Reddit, a popular and anonymousonline platform for user discussion, to qualitatively investigate patient experiences and questions surrounding vasectomy so healthcare providers may better understand patient concerns. Methods Threads, composed of a primary post to the website and associated comments, are organized into topic-focused forums known as subreddits. We collected threads from the Reddit group "Vasectomy" over a 12-month period. Terms searched included "pain," "volume," "erect," and "ED." Threads not focused on these terms were excluded. Two investigators trained in qualitative research used a modified grounded theory to independently code threads using key phrases. Similar phrases were grouped to form themes, which were refined into concepts. Results Threads discussed pain, ejaculate volume, and erectile dysfunction (ED) after vasectomy.An analysis of 87 threads with 1,052 responses revealed three themes: men on Reddit seek validation, recount their vasectomy experiences, and share anxieties. Concepts suggest men utilize the community to cope with these anxietiesand that a discrepancy exists between expectations set by physicians and patients' actual postoperative experiences. Conclusions This study provides valuable clues about patients' perspectives on vasectomy and the information they seek or share online. Discrepancies exist between patient expectations and guidance provided by urologists, suggesting a need for more tailored preoperative counseling. By actively acknowledging concerns about vasectomy, healthcare providers may potentially be able to better understand and cater to patient needs.

Improving the green mass quality with the help of heterosis breeding

The most reliable and effective way to improve both productivity and quality of green mass is the use of heterosis breeding. The purpose of the current work was to study the heterosis effect of green mass quality indicators in sorghum-Sudan hybrids developed based on cytoplasmic male sterility. The object of the study was the sorghum-Sudan hybrids developed by the Agricultural Research Center “Donskoy”. Dry matter productivity varied among the hybrids within 746-1202 g/m2 . The highest values have been observed in the combinations with the CMS-line ‘APV-1115’ (1045 g/m2 ). The heterosis effect on the dry matter productivity was found in all hybrids. Four hybrids ‘APV-1115 x Kudesnitsa’, ‘APV-1115 x ChT-22’, ‘Dzhetta x ChT-2’, ‘APV-1115 x Svetloplenchataya 4’ have significantly exceeded the standard in terms of dry matter productivity by 184-270 g/m2 with high rates of hypothetical (38.1-64.1%), true (93.2-142.0%) and competitive (19.8-28.9%) heterosis. Digestible protein yield has ranged from 49 to 84 g/m2 . Among the hybrids, the greatest heterosis effect was identified in the hybrids ‘Demetra x Svetloplenchataya 4’ (Hhyp.=43.4%, Htrue.=125.4%), ‘Dzhetta x Yaktik’ (Hhyp.=70.5%, Htrue.=142.3%), ‘APV-1115 x Kudestitsa’ (Hhyp.=72.8%, Htrue.=108.9%), ‘APV-1115 x Svetloplenchataya 2’ (Hhyp.=81.0%, Htrue.=118.4%), ‘APV1115 x ChT-22’ (Hhyp.=103.3%, Htrue.=118.4%). In the course of the study, there has been found that according to the content of crude protein, ash, oil, fiber and nitrogen-free extractive substances (NES), the most hybrids possessed partial or incomplete dominance of large values. However, to obtain even a slight heterosis according to the content of protein, fiber, and NES content, at least one parent had to have high trait values. Based on the complex of the heterotic effect according to the green mass quality indicators, there have been identified such hybrids as ‘Dzhetta x Yaktik’, which exceeded the large parental form in terms of dry matter (Htrue.=10.5%) and oil (Htrue.=14.4%); ‘Dzhetta x ChSS’ which exceeded the large parental form in terms of dry matter and crude protein (Htrue.=14.3 and 1.3%); ‘Demetra x Svetloplenchataya 4’ which exceeded the large parental form in terms of crude protein, dry matter, and ash (Htrue.=3.8; 5.9 and 6.4%, respectively). In general, the data obtained have indicated the prospects of using cytoplasmic male sterility in breeding not only for productivity, but also for quality.

A history of susceptibility to parasites and divergence in solitary, gregarious and agonistic behaviors of embiopterans.

Two species of Haploembia Ramburi (Oligotomidae: Embioptera), nonnative detritivores found in the western USA, display solitary tendencies, not typical for webspinners that usually share silk galleries. Reports from the 1960s based on native populations in Italy highlighted the impact of a gregarine that depressed male sterility and female survivorship in Haploembia solieri (Rambur). Sympatric asexual Haploembia tarsalis (Ross) lives a normal lifespan when parasitized, albeit suffering from reduced fecundity. Our goal is to characterize behavioral repertoires as individuals interact and to develop methods for future investigations focused on the impact of the little-known parasite. We quantified individual responses to conspecifics or other species in 10-min dyadic interactions and, in a 3-day trial, determined whether they aggregated when given dispersed resources. Replicated groups of four adult female H. solieri or H. tarsalis settled away from each other over the 3-day trials. In 10-min bouts of same or different species pairs, focal insects bolted back, retreated and attempted to escape when they encountered one another, especially when the opponent was H. tarsalis. Males courted conspecific females, but were dramatically repelled by H. tarsalis. Serving as a positive control, Oligotoma nigra (Hagen) (Oligotomidae) adult females paired with conspecifics displayed typical webspinner behaviors by sitting together, sharing silk. Haploembia solieri males did not respond negatively to O. nigra, not known to be parasitized by the gregarine, but did so when paired with H. tarsalis. Results align with the prediction that susceptibility to parasitism may have led to antisocial behaviors observed in two Haploembia species.

CRISPR/Cas9 and Anther Culture for Precision Double Haploid Line Production in Controlled Environments

ABSTRACTThe development of mapping populations and quantitative trait loci (QTL) analysis face constraints, in crops exhibiting male sterility and self‐incompatibility under field conditions. Addressing these challenges requires the integration of advanced techniques, including the temporal alteration or excision of centromere histone H3 (CENH3) protein and the use of gene editing tools such as MATRILINEAL (MTL) knockout. Specifically, this can be achieved through Cas9/gRNA‐mediated mutagenesis or Cas9/gRNA‐driven promoter expression systems. These technologies offer efficient means to advance mapping populations and QTL analysis in male sterile and self‐incompatible crops within controlled ecosystems. The doubled haploid (DH) mapping population, traditionally requiring 3 years of generation time via anther culture method, can now be expedited to 2–3 years of generation time using gene editing techniques within controlled environmental systems. Notably, DH mapping populations can be efficiently generated in various crops, including rice, wheat, maize, barley and oats by leveraging gene editing tools. Among these tools, the novel approach of CENH3 protein temporal alteration/excision emerges as highly efficient compared to MTL knockout using Cas9/gRNA‐mediated mutation or Cas9/gRNA promoter expression. However, further investigation is warranted to optimise the regeneration of double haploid populations and enhance QTL analysis in male sterile and self‐incompatible crops under controlled systems.

The effect of T. aestivum chromosomes 1A and 1D on fertility of alloplasmic recombinant (H. vulgare)-T. aestivum lines depending on cytonuclear compatibility.

The effect of T. aestivum L. chromosomes 1A and 1D on fertility of recombinant bread wheat allolines of the same origin carrying the cytoplasm of barley H. vulgare L. and different levels of cytonuclear compatibility was studied. Alloline L-56 included mainly fully sterile (FS) and partially sterile (PS) plants, alloline L-57 included partially fertile (PF) plants and line L-58 included fertile (F) ones. Analysis of morphobiological traits and pollen painting indicated complete or partial male sterility in plants of allolines L-56 and L-57. To differentiate genotypes with cytonuclear coadaptation and genotypes with cytonuclear incompatibility, PCR analysis of the 18S/5S mitochondrial (mt) repeat was performed. Heteroplasmy (simultaneous presence of barley and wheat mtDNA copies) was found in FS, PS, PF and some F plants, which was associated with a violation of cytonuclear compatibility. Wheat-type homoplasmy (hm) was detected in the majority of the fertile plants, which was associated with cytonuclear coadaptation. The allolines used as maternal genotypes were crossed with wheat-rye substitution lines 1R(1A) and 1R(1D). In F1, all plants of PF×1R(1A) and PF×1R(1D) combinations were fertile, and in F2, a segregation close to 3 (fertile) : 1 (sterile) was observed. These results showed for the first time that chromosomes 1A and 1D carry one dominant Rf gene, which controls the restoration of male fertility of bread wheat carrying the cytoplasm of H. vulgare. All plants of F1 combinations FS×1R(1A), FS×1R(1D), PS×1R(1A), PS×1R(1D) were sterile, which indicates that a single dose of genes localized on wheat chromosomes 1A or 1D is not enough to restore male fertility in FS and PS plants. All plants of hybrid combinations F(hm)×1R(1A) and F(hm)×1R(1D) in both F1 and F2 were fertile, that is, fertility of allolines with cytonuclear coadaptation does not depend on wheat chromosomes 1A and 1D.

Sharp decline in male fertility in F2 hybrids of the female-heterogametic silk moth Bombyx.

Sexual selection drives rapid evolution of morphological, physiological, and behavioral traits, especially in males, and it may also drive the rapid evolution of hybrid male sterility. Indeed, the faster male theory of speciation was once viewed as a major cause of Haldane's rule in male-heterogametic XY taxa, but is increasingly being replaced by the genetic conflict hypothesis partly because it cannot explain the faster evolution of hybrid female sterility in female-heterogametic ZW taxa. The theory nonetheless predicts that there should be more genes for hybrid male sterility than for hybrid female sterility even in such taxa, but this remains untested. Thus, finding evidence for the faster male theory of reproductive isolation beyond the F1 generation in ZW systems still represents a challenge to studying the impact of sexual selection. In this study, we examined F2 hybrids between the domesticated silkworm Bombyx mori and the wild silk moth Bombyx mandarina, which have ZW sex determination. We found that although only females showed reduced fertility in the F1 generation, the F2 hybrid males had a significant reduction in fertility compared with the parental and F1 males. Importantly, 27% of the F2 males and 15% of the F2 females were completely sterile, suggesting the presence of recessive incompatibilities causing male sterility in female-heterogametic taxa.

Vasectomy provider decision-making balancing autonomy and non-maleficence: qualitative interviews with providers

Background Male sterilization, or vasectomy, is 99.9% effective at preventing pregnancy with less than a 2% risk of complications. Despite the high efficacy, low risk, low cost, and gender equity benefits of vasectomy, just 2% of women reported that they and their partners relied on vasectomy as their contraceptive method globally in 2019. Health care providers can be both a facilitator and a barrier in men’s health generally, and may be in vasectomy provision as well. This study sought to describe the decision-making rationales of experienced vasectomy providers when evaluating patient candidacy in complex cases. Methods Fifteen vasectomy providers belonging to the global Vasectomy Network Google Group from seven countries participated in online interviews using a semi-structured in-depth interview guide. Providers were asked about their vasectomy training, their reasons for vasectomy provision, challenging cases they have faced, and approaches used to manage challenging cases. Vignettes were used to further elicit decision-making rationale. Thematic analysis was conducted using MAXQDA20. Results Provider decision-making was predicated on ensuring patients were well-informed, able to consent, and certain about their choice to have a vasectomy. Once those foundational conditions were met, providers filtered patient characteristics through their training, laws and policies, sociocultural norms, experience, and peer influence to produce a cost-benefit breakdown. Based on the cost-benefit analysis, providers determined whether to weigh autonomy or non-maleficence more heavily when determining vasectomy patient candidacy. Conclusions Despite clinical best practices that promote prioritizing patient autonomy over non-maleficence, some providers continued to weigh non-maleficence over autonomy in vasectomy patient candidacy evaluations. Non-maleficence was particularly prioritized in cases providers deemed to be at higher risk of regret. The findings of this study suggest vasectomy provider training should emphasize evidence-based best practices in shared decision-making and patient-centered care to facilitate vasectomy provision that honors patient autonomy and rights.

Heat Stress Inhibits Pollen Development by Degrading mRNA Capping Enzyme ARCP1 and ARCP2.

Pollen development and germination are critical for successful generation of offspring in plants, yet they are highly susceptible to heat stress (HS). However, the molecular mechanism underlying this process has not been fully elucidated. In this study, we highlight the essential roles of two mRNA capping enzymes, named Arabidopsis mRNA capping phosphatase (ARCP) 1 and 2, in regulating male and female gamete development. The transmission efficiencies of gametes carrying arcp1 arcp2 from arcp1+/- arcp2-/- and arcp1-/- arcp2+/- mutants are 30% and zero, respectively. These mutants exhibited a significant increase in misshaped pollen, with germination rates approximately half of those in wild type. ARCP1/2 exhibit RNA triphosphatase and RNA guanylyltransferase activities, which are required for proper pollen development. Through RNA-seq analysis, genes involved in pollen development/germination and HS response were identified as downregulated genes in pollen from arcp1+/- arcp2-/- mutant. Furthermore, ARCP2 protein is degraded under HS condition, and inducing the expression of ARCP2 can increase the pollen germination rate under elevated temperature. We propose that HS triggers the degradation of mRNA capping enzymes, which in turn disrupts the transcriptome that required for pollen development and pollen germination and ultimately leads to male sterility.

Fertility restorer gene CaRf and PepperSNP50K provide a promising breeding system for hybrid pepper.

Cytoplasmic male sterility (CMS) is pivotal in plant breeding and widely employed in various crop hybrids, including pepper. However, the functional validation of the restorer of fertility (Rf) gene in pepper has been lacking until now. This study identifies and characterizes CaRf, a single dominant locus crucial for restoring CMS in the pepper strong recovery inbred line Zhangshugang. The CaRf gene encodes a mitochondria-targeted pentatricopeptide repeat protein, validated through the induction of male sterility upon its silencing in hybrid F1 plants. To enhance pepper breeding efficiency, 176 important pepper breeding parent materials were resequenced, and a PepperSNP50K liquid-phase breeding chip was developed, comprising 51 172 markers. Integration of CaRf functional characterization and PepperSNP50K facilitated the development of a high-quality red pepper hybrid. These findings provide significant insights and practical strategies for advancing molecular-designed breeding in peppers.

Disruption of Energy Metabolism and Reactive Oxygen Species Homeostasis in Honglian Type-Cytoplasmic Male Sterility (HL-CMS) Rice Pollen

Honglian type-cytoplasmic male sterility (HL-CMS) is caused by the inter-communication between the nucleus and mitochondria. However, the mechanisms by which sterility genes regulate metabolic alterations and changes in mitochondrial morphology in the pollen of HL-CMS remains unclear. In this study, we compared the morphological differences between the pollen of the male sterile line YA and the near-isogenic line NIL-Rf6 using hematoxylin and eosin staining as well as 4ʹ,6-diamidino- 2-phenylindole (DAPI) staining. HL-CMS is characterized by gametophytic sterility, where the aborted pollen grains are empty and the tapetal layer remains intact. Transmission electron microscopy was employed to observe mitochondrial morphological changes at the microspore stage, revealing that significant mitochondrial alternations, characterized by the formation of 'large spherical mitochondria', occurred at the binucleate stage in the YA line. Additionally, metabolomics analysis revealed decreased levels of metabolites associated with the carbohydrate and flavonoid pathways. Notably, the decrease in flavonoids was found to contribute to an elevation in reactive oxygen species (ROS) levels. Therefore, we propose a model in which rice fertility is modulated by the levels of pollen carbohydrates and flavonoid metabolites, with impaired mitochondrial energy production and reduced flavonoid biosynthesis being the main causes of ROS accumulation and pollen abortion in rice.

Identification of stable restorers and high-yielding hybrids using diverse sorghum male sterile cytoplasmic sources and established pollen parents under different water regimes

Sorghum hybrids demonstrated increased productivity and helped offset the decreasing cultivated areas, particularly in Asia. The diversity in cytoplasmic male sterility systems, stability of restorers and high yield of sorghum is an important factor for achieving food security and sustainability. In sorghum, hybrid production has been limited to A1 cytoplasmic source to date, primarily due to limited number of restorers on other cytoplasmic sources. This work aimed at filling this gap through diversifying and assessing the producibility and stability of cytoplasmic backgrounds across environments, evaluating the stability of restorers across cytoplasms and environments, and evaluating the performance of the hybrid F1 products under different water regimes across cropping seasons. The effects of genotypes and interactions between the genotypes and the tested environments were shown visually using GGE biplot, which also categorized the genotypes based on performance per se and stability. Analysis of variance revealed significant (P< 0.001) differences between genotypes, environments and their interaction components for all the plant characteristics studied. The various GGE biplot patterns revealed that the restorers G4 (IS 33844-5), G5 (M 35-1-19), G8 (ICSV 15014), and G10 (ICSR 13009) were stable across environments and cytoplasms. We observed the following order of superiority in cytoplasmic restoration and seed producibility, A2 >A1>A3 >A4. The A2 cytoplasm can therefore reliably offer seed producibility advantage to commercial seed producers. Furthermore, the which-won–where model for hybrid grain yield revealed specific adaptations of hybrid genotypes G143, G195 and G215 to first mega environment (E1 and E3), whereas G167, G110, and G112 were adapted to the second mega-environment (E2 and E4). With a GGE biplot goodness of fit of 70% the best possible yield- and stability-based ranking of hybrid genotypes was G143, G215, G189, G200, G69, G162, G119, G54, and G81. The newly uncovered hybrid products should therefore be considered for downstream testing stages and candidates for release and commercial cultivation. Clearly, this work resulted in novel findings particularly in terms of seed producibility, universal restorers across the 4 cytoplasms and environments, and superior and stable hybrid products, all of which are expected to add value to conventional and heterosis breeding in the process of sorghum cultivar development.

Assembly and comparative analysis of the mitochondrial genome in diploid potatoes.

We report the mitochondrial genome of 39 diploid potatoes and identify a candidate ORF potentially linked to cytoplasmic male sterility in potatoes. Potato (Solanum tuberosum L.) holds a critical position as the foremost non-grain food crop, playing a pivotal role in ensuring global food security. Diploid potatoes constitute a vital genetic resource pool, harboring the potential to revolutionize modern potato breeding. Nevertheless, diploid potatoes are relatively understudied, and mitochondrial DNA can provide valuable insights into key potato breeding traits such as CMS. In this study, we examine and assemble the mitochondrial genome evolution and diversity of 39 accessions of diploid potatoes using high-fidelity (HiFi) sequencing. We annotated 54 genes for all the investigated accessions, comprising 34 protein-coding genes, 3 rRNA genes, and 17 tRNA genes. Our analyses revealed differences in repeats sequences between wild and cultivated landraces. To understand the evolution of diploid maternal lineage inheritance, we conducted phylogenetic analysis, which clearly distinguished mitochondrial from nuclear gene trees, further supporting the evidence-based of clustering between wild and cultivated landraces accessions. Our study discovers new candidate ORFs associated with CMS in potatoes, including ORF137, which is homologous to other CMS in Solanaceae. Ultimately, this work bridges the gap in mitochondrial genome research for diploid potatoes, providing a steppingstone into evolutionary studies and potato breeding.

Identification and variation of a new restorer of fertility gene that induces cleavage in orf138 mRNA of Ogura male sterility in radish

Key messageA new restorer of fertility gene, Rfs, of Ogura cytoplasmic male sterility (CMS) in radish encodes a pentatricopeptide repeat protein that binds to 15 nucleotides in mRNA of the CMS gene, orf138. Nucleotide substitutions in both Rfs and orf138 determine effectiveness and specificity of restoration.Cytoplasmic male sterility (CMS) in plants caused by the expression of abnormal mitochondrial genes results from impaired pollen production. The manifestation of CMS is suppressed by the restorer of fertility (Rf) genes in the nuclear genome. Thus, the CMS-Rf system is a suitable model for studying the direct interactions of mitochondrial and nuclear genes. At least nine haplotypes, of which Type B is ancestry, have been reported for the Ogura CMS gene, orf138, in radish (Raphanus sativus). We previously observed that Rfo encoding a pentatricopeptide repeat (PPR) protein, ORF687, which inhibits the translation of orf138 is ineffective in one haplotype (i.e., Type H). Here, we carried out map-based cloning of another Rf gene (Rfs) that cleaves the orf138 mRNA of Type H. Rfs produces a PPR protein consisting of 15 PPR motifs that binds to the mRNA, cleaving the mRNA at about 50nt downstream of the binding site. However, Rfs was ineffective for Type A because of a single nucleotide substitution in the binding site. Both Rfo and Rfs suppress orf138 expression in ancestral Type B, but they are rendered ineffective in Type H and Type A, respectively, by a single nucleotide substitution in orf138.

Improvement of Quality and Disease Resistance for a Heavy-Panicle Hybrid Restorer Line, R600, in Rice (Oryza sativa L.) by Gene Pyramiding Breeding.

The utilization of heavy-panicle hybrid rice exemplifies the successful integration of architectural enhancement and heterosis, which has been widely adopted in the southwest rice-producing area of China. Iterative improvement in disease resistance and grain quality of heavy-panicle hybrid rice varieties is crucial to promote their sustainable utilization. Here, we performed a molecular design breeding strategy to introgress beneficial alleles of broad-spectrum disease resistance and grain quality into a heavy-panicle hybrid backbone restorer line Shuhui 600 (R600). We successfully developed introgression lines through marker-assisted selection to pyramid major genes (Wxb + ALKA-GC + Pigm + Xa23) derived from three parents (Huanghuazhan, I135, I488), which significantly enhance grain quality and confer resistance to rice blast and bacterial blight (BB). The improved parental R600 line (iR600) exhibited superior grain quality and elevated disease resistance while maintaining the heavy-panicle architecture and high-yield capacity of R600. Moreover, the iR600 was crossed with male sterility line 608A to obtain a new heavy-panicle hybrid rice variety with excellent eating and cooking quality (ECQ) and high yield potential. This study presents an effective breeding strategy for rice breeders to expedite the improvement of grain quality and disease resistance in heavy-panicle hybrid rice.

Genome-Wide Identification, Characterization, and Expression Pattern Analysis of the JAZ Gene Family in Wax Apple (Syzygium samarangense)

Wax apple (Syzygium samarangense) is a characteristic tropical fruit with great potential value, but the cold sensitivity and male sterility limit its cultivation and breeding. Despite the important role in JA-mediated cold-stress resistance and flower development, jasmonate ZIM-domain (JAZ) proteins have not been identified in wax apple. This study employed sequence blast, phylogenetic analysis, and RT-PCR to identify SsJAZs in wax apple systematically. First, 14 SsJAZs family members with TIFY and Jas domains were identified and named according to the distribution on ten chromosomes. Low-temperature responsiveness elements and TGACG-motif (response to MeJA) were abundant in the promoters of most SsJAZs. The transcription factors ERF and MYB were predicted to be involved in the regulation of SsJAZs. RT-PCR analyses showed that SsJAZs were mainly expressed in mature leaves and flowers. Further analysis revealed differences in the expression patterns of SsJAZs under cold treatment, as well as in different anther stages. SsJAZ proteins were predicted to interact with the N terminus of SsMYC2 protein via the Jas motif at the C-terminal domain. This study characterized the SsJAZs family members and examined the expression patterns in different samples. The results will advance our understanding of the role of SsJAZs in wax apple.

An explanation for the prevalence of XY over ZW sex determination in species derived from hermaphroditism

The many independent transitions from hermaphroditism to separate sexes (dioecy) in flowering plants and some animal clades must often have involved the emergence of a heterogametic sex-determining locus, the basis of XY and ZW sex determination (i.e., male and female heterogamety). Current estimates indicate that XY sex determination is much more frequent than ZW, but the reasons for this asymmetry are unclear. One proposition is that separate sexes evolve through the invasion of sterility mutations at closely linked loci, in which case XY sex determination evolves if the initial male sterility mutation is fully recessive. Alternatively, dioecy may evolve via the gradual divergence of male and female phenotypes, but the genetic basis of such divergence and its connection to XY and ZW systems remain poorly understood. Using mathematical modeling, we show how dioecy with XY or ZW sex determination can emerge from the joint evolution of resource allocation to male and female function with its genetic architecture. Our model reveals that whether XY or ZW sex determination evolves depends on the trade-off between allocation to male and female function, and on the mating system of the ancestral hermaphrodites, with selection for female specialization or inbreeding avoidance both favoring XY sex determination. Together, our results cast light on an important but poorly understood path from hermaphroditism to dioecy, and provide an adaptive hypothesis for the preponderance of XY systems. Beyond sex and sex determination, our model shows how ecology can influence the way selection shapes the genetic architecture of polymorphic traits.

Sperm Storage and Use Following Multiple Insemination in Aedes albopictus: Encouraging Insights for the Sterile Insect Technique.

The key to success in the application of the sterile insect technique (SIT) relies on the ability of released, sterile males to outcompete their fertile wild male counterparts to mate with wild females. However, many insect species exhibit multiple-mating behavior, which can be a way for females to select paternity for their progeny. This study aims to recognize the consequences of potential double-matings during an SIT program and to detect any evidence of sperm selection favoring sperm from fertile mates. This report provides a descriptive analysis of the storage and use of sperm by female Aedes albopictus. Stable isotopes were used to mark the sperm of fertile and sterile males. Mated females were allowed to oviposit before dissecting the spermathecae to link the presence of each type of sperm to the sterility of the eggs laid. It was found that sperm in females inseminated by both males was distributed in the three spermathecae with no obvious pattern, mostly mixed but also separately, and no evidence of any mechanism for sperm selection, sperm precedence, or sperm competition in Ae. albopictus females could be found. The fact that only a few double-mated females were double-inseminated and could also produce semi-sterile eggs, together with the finding that the sperm of sterile males appeared to be no less viable than that of fertile males, is an encouraging outcome for SIT approaches.

Different complex regulatory phenotypes underlie hybrid male sterility in divergent rodent crosses.

Hybrid incompatibilities are a critical component of species barriers and may arise due to negative interactions between divergent regulatory elements in parental species. We used a comparative approach to identify common themes in the regulatory phenotypes associated with hybrid male sterility in two divergent rodent crosses, dwarf hamsters and house mice. We investigated three potential characteristic gene expression phenotypes in hybrids including the propensity of transgressive differentially expressed genes in hybrids towards over or underexpression relative to parental species, the influence of developmental stage on the extent of misexpression, and the role of the sex chromosomes on misexpression phenotypes. In contrast to near pervasive overexpression in hybrid house mice, we found that misexpression in hybrid dwarf hamsters was dependent on developmental stage. In both house mouse and dwarf hamster hybrids, however, transgressive misexpression increased with the progression of spermatogenesis, although to varying extents and with potentially different consequences. In both systems, we detected sex-chromosome specific overexpression in stages of spermatogenesis where inactivated X chromosome expression was expected, but the hybrid overexpression phenotypes were fundamentally different. Importantly, misexpression phenotypes support the presence of multiple developmental blocks to spermatogenesis in dwarf hamster hybrids, including a potential role of meiotic stalling or breakdown early in spermatogenesis. Collectively, we demonstrate that while there are some similarities in hybrid expression phenotypes of house mice and dwarf hamsters, there are also clear differences that point towards unique mechanisms underlying hybrid male sterility in each system. Our results highlight the potential of comparative approaches in helping to understand the causes and consequences of disrupted gene expression in speciation.

Characterization of the complete mitogenome of Tiarella polyphylla, commonly known as Asian foamflower: insights into the multi-chromosomes structure and DNA transfers

BackgroundTiarella polyphylla D. Don has been traditionally used to cure asthma and skin eruptions. However, the sequence and the structure of the mitogenome of T. polyphylla remained elusive, limiting the genomic and evolution analysis based on the mitogenome.ResultsUsing a combination of Illumina and Nanopore sequencing reads, we de novo assembled the complete mitogenome of T. polyphylla. In addition to unveiling the major configuration of the T. polyphylla mitogenome was three circular chromosomes with lengths of 430,435 bp, 126,943 bp, and 55,269 bp, we revealed five (R01-R05) and one (R06) repetitive sequence could mediate the intra- and inter-chromosomal recombination, respectively. Furthermore, we identified 208 short and 25 long tandem segments, seven cp-derived mtDNAs, 106 segments of mtDNAs transferred to the nuclear genome, and 653 predicted RNA editing sites. Based on the sequence of the mitogenomes, we obtained the resolved phylogeny of the seven Saxifragales species.ConclusionsThese results presented the mitogenome features and expanded its potential applications in phylogenetics, species identification, and cytoplasmic male sterility (CMS) in the future.