Association of early cleavage, morula compaction and blastocysts ploidy of IVF embryos cultured in a time-lapse system and biopsied for genetic test for aneuploidy.

IVF embryos have historically been evaluated by morphological characteristics. The time-lapse system (TLS) has become a promising tool, providing an uninterrupted evaluation of morphological and dynamic parameters of embryo development. Furthermore, TLS sheds light on unknown phenomena such as direct cleavage and incomplete morula compaction. We retrospectively analyzed the morphology (Gardner Score) and morphokinetics (KIDScore) of 835 blastocysts grown in a TLS incubator (Embryoscope+), which were biopsied for preimplantation genetic testing for aneuploidy (PGT-A). Only the embryos that reached the blastocyst stage were included in this study and time-lapse videos were retrospectively reanalysed. According to the pattern of initial cleavages and morula compaction, the embryos were classified as: normal (NC) or abnormal (AC) cleavage, and fully (FCM) or partially compacted (PCM) morulae. No difference was found in early cleavage types or morula compaction patterns between female age groups (< 38, 38-40 and > 40 yo). Most of NC embryos resulted in FCM (≅ 60%), while no embryos with AC resulted in FCM. Aneuploidy rate of AC-PCM group did not differ from that of NC-FCM group in women < 38 yo, but aneuploidy was significantly higher in AC-PCM compared to NC-FCM of women > 40 yo. However, the quality of embryos was lower in AC-PCM blastocysts in women of all age ranges. Morphological and morphokinetic scores declined with increasing age, in the NC-PCM and AC-PCM groups, compared to the NC-FCM. Similar aneuploidy rates among NC-FCM and AC-PCM groups support the hypothesis that PCM in anomalous-cleaved embryos can represent a potential correction mechanism, even though lower morphological/morphokinetic scores are seen on AC-PCM. Therefore, both morphological and morphokinetic assessment should consider these embryonic development phenomena.

DNA content and clinicopathological features aid in distinguishing ameloblastic carcinoma from ameloblastoma.

BACKGROUND: Ameloblastoma and ameloblastic carcinoma are epithelial odontogenic tumors that can be morphologically similar. In the present study, we evaluated the DNA content and Ki-67 index in the two tumors. METHODS: The paraffin blocks of the tumors were selected to obtain sections for the immunohistochemical reactions and preparation of the cell suspension for acquisition in a flow cytometer. The Random Forest package of the R software was used to verify the contribution of each variable to classify lesions into ameloblastoma or ameloblastic carcinoma. RESULTS: Thirty-two ameloblastoma and five ameloblastic carcinoma were included in the study. In our sample, we did not find statistically significant differences in Ki-67 labeling rates. A higher fraction of cells in 2c (G1) was correlated with the diagnosis of ameloblastoma, whereas higher rates of 5c-exceeding rate (5cER) were correlated with ameloblastic carcinoma. The Random Forest model highlighted histopathological findings and parameters of DNA ploidy study as important features for distinguishing ameloblastoma from ameloblastic carcinoma. CONCLUSION: Our findings suggest that the parameters of the DNA ploidy study can be ancillary tools in the classification of ameloblastoma and ameloblastic carcinoma.

Alternative Evolutionary Pathways in Paspalum Involving Allotetraploidy, Sexuality, and Varied Mating Systems.

The genetic systems of Paspalum species have not been extensively studied. We analyzed the ploidy, reproductive mode, mating system, and fertility of four Paspalum species-Paspalum durifolium, Paspalum ionanthum, Paspalum regnellii, and Paspalum urvillei. An analysis of 378 individuals from 20 populations of northeastern Argentina was conducted. All populations of the four Paspalum species were pure tetraploid and had a sexual and stable reproductive mode. However, some populations of P. durifolium and P. ionanthum showed low levels of apospory. Populations of P. durifolium and P. ionanthum had low seed sets under self-pollination but were fertile under open pollination, showing that self-incompatibility likely caused self-sterility. In contrast, populations of P. regnellii or P. urvillei showed no evidence of apospory, and seed sets in both self- and open pollination conditions were high, suggesting that they are self-compatible due to the absence of pollen-pistil molecular incompatibility mechanisms. The evolutionary origin of the four Paspalum species could explain these differences. This study supplies valuable insights into the genetic systems of Paspalum species, which could have implications for their conservation and management.

DNA ploidy and stroma predicted the risk of recurrence in low-risk stage III colorectal cancer.

BACKGROUND: For clinically low-risk stage III colorectal cancer, the decision on cycles of adjuvant chemotherapy after surgery is disputed. The present study investigates the use of additional biomarkers of ploidy and stroma-ratio(PS) to stratify patients with low-risk stage III colorectal cancer, providing a basis for individualized treatment in the future. METHODS: This study retrospectively enrolled 198 patients with clinical-low-risk stage III colorectal cancer (T1-3N1M0) and analyzed the DNA ploidy and stroma ratio of FFPE tumor tissues. The patients were divided into PS-low-risk group (Diploidy or Low-stroma) and PS-high-risk group (Non-diploid and High-stroma). For survival analyses, Kaplan-Meier and Cox regression models were used. RESULTS: The results showed that the 5-year DFS of the PS-high-risk group was significantly lower than that in the PS-low-risk group (78.6 vs. 91.2%, HR = 2.606 [95% CI: 1.011-6.717], P = 0.039). Besides, in the PS-low-risk group, the 5 year OS (98.2 vs. 86.7%, P = 0.022; HR = 5.762 [95% CI: 1.281-25.920]) and DFS (95.6, vs 79.9%, P = 0.019; HR = 3.7 [95% CI: 1.24-11.04]) of patients received adjuvant chemotherapy for > 3 months were significantly higher than those received adjuvant chemotherapy for < 3 months. We also found that the PS could stratify the prognosis of patients with dMMR tumors. The 5-year OS (96.3 vs 71.4%, P = 0.037) and DFS (92.6 vs 57.1%, P = 0.015) were higher in the PS-low-risk dMMR patients than those in the PS-high-risk dMMR patients. CONCLUSION: In this study, we found that PS can predict the prognosis of patients with stage III low-risk CRC. Besides, it may guide the decision on postoperative adjuvant chemotherapy.

Characterization of a new cytotype and ocurrence of a B microchromosome in two spot astyanax, Astyanax bimaculatus Linnaeus, 1758 (Characiformes: Characidae).

Although Astyanax bimaculatus is the most representative species of the genus in the Amazon region, there are no cytogenetic studies of A. bimaculatus species in Amazon region. Thus, we aimed to analyse the chromosome complements of specimens from this area using classic and molecular cytogenetic approaches. The results revealed the existence of a distinct cytotype and this is the first report of the occurrence of a B microchromosome in the species. Overall, these data indicate that the karyotypic evolution of this species is complex, involving the occurrence of chromosomal rearrangements.

Impact of inactivated SARS-CoV-2 vaccination on embryo ploidy: a retrospective cohort study of 133 PGT-A cycles in China.

BACKGROUND: Unsubstantiated concerns have been raised on the potential correlation between severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination and infertility, leading to vaccine hesitancy in reproductive-aged population. Herein, we aim to evaluate the impact of inactivated SARS-CoV-2 vaccination on embryo ploidy, which is a critical indicator for embryo quality and pregnancy chance. METHODS: This was a retrospective cohort study of 133 patients who underwent preimplantation genetic testing for aneuploidy (PGT-A) cycles with next-generation sequencing technology from June 1st 2021 to March 17th 2022 at a tertiary-care medical center in China. Women fully vaccinated with two doses of Sinopharm or Sinovac inactivated vaccines (n = 66) were compared with unvaccinated women (n = 67). The primary outcome was the euploidy rate per cycle. Multivariate linear and logistic regression analyses were performed to adjust for potential confounders. RESULTS: The euploidy rate was similar between vaccinated and unvaccinated groups (23.2 ± 24.6% vs. 22.6 ± 25.9%, P = 0.768), with an adjusted ß of 0.01 (95% confidence interval [CI]: -0.08-0.10). After frozen-thawed single euploid blastocyst transfer, the two groups were also comparable in clinical pregnancy rate (75.0% vs. 60.0%, P = 0.289), with an adjusted odds ratio of 6.21 (95% CI: 0.76-50.88). No significant associations were observed between vaccination and cycle characteristics or other laboratory and pregnancy outcomes. CONCLUSIONS: Inactivated SARS-CoV-2 vaccination had no detrimental impact on embryo ploidy during in vitro fertilization treatment. Our finding provides further reassurance for vaccinated women who are planning to conceive. Future prospective cohort studies with larger datasets and longer follow-up are needed to confirm the conclusion.

Root/shoot responses to drought and flooding of bahiagrass at reproductive stage depends on genotype ploidy.

Severe water stress is responsible for reducing plant growth and reproduction. This study aimed to evaluate the physiological and biochemical mechanisms associated with the tolerance of two genotipes of bahiagrass (Paspalum notatum Flügge) with different ploidy level to water deficit and flooding at the reproductive stage. Photosynthetic performance of diploid and tetraploid plants was not affected by flooding. In contrast, the water deficit decreased stomatal conductance, increased leaf temperature, and resulted in a decrease in the assimilation rate of the two genotypes. Despite the greater activities of antioxidant enzymes, flooded roots accumulated hydrogen peroxide and malondialdehyde. Roots of plants exposed to water deficit maintained an accumulation of biomass similar to that of control plants; however, with higher levels of total phenol content, total soluble sugars and proline. Diploid plants subjected to flooding had more inflorescences, however, the drought reduced the total number of filled florets per plant. Less starch degradation allows the maintenance and recovery of biomass in the tetraploid genotype, which allows it to maintain its reproductive performance even under drought conditions. Overall, the synthesis of osmoprotectants and activation of antioxidant machinery are important strategies in the tolerance of bahiagrass to water stress at the reproductive stage.

Impact of inactivated SARS-CoV-2 vaccination on embryo ploidy: a retrospective cohort study of 133 PGT-A cycles in China

BACKGROUND: Unsubstantiated concerns have been raised on the potential correlation between severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination and infertility, leading to vaccine hesitancy in reproductive-aged population. Herein, we aim to evaluate the impact of inactivated SARS-CoV-2 vaccination on embryo ploidy, which is a critical indicator for embryo quality and pregnancy chance. METHODS: This was a retrospective cohort study of 133 patients who underwent preimplantation genetic testing for aneuploidy (PGT-A) cycles with next-generation sequencing technology from June 1st 2021 to March 17th 2022 at a tertiary-care medical center in China. Women fully vaccinated with two doses of Sinopharm or Sinovac inactivated vaccines (n = 66) were compared with unvaccinated women (n = 67). The primary outcome was the euploidy rate per cycle. Multivariate linear and logistic regression analyses were performed to adjust for potential confounders. RESULTS: The euploidy rate was similar between vaccinated and unvaccinated groups (23.2 ± 24.6% vs. 22.6 ± 25.9%, P = 0.768), with an adjusted ß of 0.01 (95% confidence interval [CI]: -0.08-0.10). After frozen-thawed single euploid blastocyst transfer, the two groups were also comparable in clinical pregnancy rate (75.0% vs. 60.0%, P = 0.289), with an adjusted odds ratio of 6.21 (95% CI: 0.76-50.88). No significant associations were observed between vaccination and cycle characteristics or other laboratory and pregnancy outcomes. CONCLUSIONS: Inactivated SARS-CoV-2 vaccination had no detrimental impact on embryo ploidy during in vitro fertilization treatment. Our finding provides further reassurance for vaccinated women who are planning to conceive. Future prospective cohort studies with larger datasets and longer follow-up are needed to confirm the conclusion.

Chromosome Number, Ploidy Level, and Nuclear DNA Content in 23 Species of Echeveria (Crassulaceae).

Echeveria is a polyploid genus with a wide diversity of species and morphologies. The number of species registered for Echeveria is approximately 170; many of them are native to Mexico. This genus is of special interest in cytogenetic research because it has a variety of chromosome numbers and ploidy levels. Additionally, there are no studies concerning nuclear DNA content and the extent of endopolyploidy. This work aims to investigate the cytogenetic characteristics of 23 species of Echeveria collected in 9 states of Mexico, analyzing 2n chromosome numbers, ploidy level, nuclear DNA content, and endopolyploidy levels. Chromosome numbers were obtained from root tips. DNA content was obtained from the leaf parenchyma, which was processed according to the two-step protocol with Otto solutions and propidium iodide as fluorochrome, and then analyzed by flow cytometry. From the 23 species of Echeveria analyzed, 16 species lacked previous reports of 2n chromosome numbers. The 2n chromosome numbers found and analyzed in this research for Echeveria species ranged from 24 to 270. The range of 2C nuclear DNA amounts ranged from 1.26 pg in E. catorce to 7.70 pg in E. roseiflora, while the 1C values were 616 Mbp and 753 Mbp, respectively, for the same species. However, differences in the level of endopolyploidy nuclei were found, corresponding to 4 endocycles (8C, 16C, 32C and 64C) in E. olivacea, E. catorce, E. juarezensis and E. perezcalixii. In contrast, E. longiflora presented 3 endocycles (8C, 16C and 32C) and E. roseiflora presented 2 endocycles (8C and 16C). It has been suggested that polyploidization and diploidization processes, together with the presence of endopolyploidy, allowed Echeveria species to adapt and colonize new adverse environments.

Chromosomal Instability and Origin of B Chromosomes in the Amazonian Glass Tetra Moenkhausia oligolepis (Günther, 1864) (Characiformes, Characidae).

B chromosomes occur in different species of the small characid fishes of the genus Moenkhausia. These supernumerary elements, that do not recombine with chromosomes of the standard A complement and follow their own evolutionary mechanism vary in number, morphology, and distribution. Here, we show karyotypic data of individuals of 2 populations of Moenkhausia oligolepis of the Brazilian Amazon (Pedro Correia and Taboquinha streams, Tocantins river basin), both with a diploid number of 50 chromosomes and karyotypic formula of 10m + 32sm + 8a. In addition to the normal complement, we also observed the occurrence of B chromosomes in the 2 populations with intra- and interindividual variation ranging from 0 to 10 Bs, independent of sex. The C-banding pattern evidenced heterochromatic blocks located mainly in the pericentromeric region of the chromosomes, while the B chromosomes appeared euchromatic. Silver-stained nucleolus organizer regions were identified in multiples sites, and some of these blocks were positive when stained with chromomycin A3. The karyotype analysis and the application of whole-chromosome painting in populations of M. oligolepis reinforce the conservation of the basal diploid number for the genus, as well as the evolutionary tendency in these fishes to carry B chromosomes. Both populations turned out to be in different stages of stability and expansion of their B chromosomes. We further suggest that the origin of these chromosomes is due to the formation of isochromosomes. Here, we identified a pair of complement A chromosomes involved in this process.

Return temperature after heat shock affects the production of tetraploids in the yellowtail tetra Astyanax altiparanae.

The aim of this study was to evaluate different post-shock temperatures for tetraploid induction in the yellowtail tetra Astyanax altiparanae. Newly fertilized eggs were divided into four groups, three were submitted to heat shock (40°C for 2 min) at 24 min post-fertilization (mpf) and another group remained without shock (control). Groups submitted to temperature shock were further separated at the following temperatures: 22°C, 26°C and 28°C. Survival among embryonic development was counted and at hatching the ploidy was analyzed by flow cytometry. The results showed that the post-shock temperature affects the parameters analyzed and, therefore, must be considered for optimization of the production of tetraploid in A. altiparanae. Those data are innovative and could be used in future studies of basic biology in this species.

Population Genetics of Polyploid Complex Psidium cattleyanum Sabine (Myrtaceae): Preliminary Analyses Based on New Species-Specific Microsatellite Loci and Extension to Other Species of the Genus.

Polyploidy is a phenomenon that alters the genetic diversity of populations and has been reported as one of the most important evolutionary forces for plant diversification. The Psidium cattleyanum complex comprises a group of wild populations with several ploidy levels reported in the literature. The multiple cytotypes, associated with its wide distribution area, make this species a potential key model for understanding evolutionary processes related to polyploidization. In this study, we isolated and characterized nuclear microsatellite markers of P. cattleyanum and tested their transferability to other nine species of the genus. We performed a preliminary analysis of genetic diversity and population structure in three populations of P. cattleyanum. The three populations analyzed had different chromosome numbers, being polyploid cytotypes (2n = 6x = 66, 2n = 7x = 77 and 2n = 8x = 88). We designed 46 primer pairs and successfully amplified 37 markers, from which the 10 best were selected for analysis. Considering both the PIC and DP values, most of markers were highly informative. The new SSR markers were used to assess the levels of genetic diversity of the populations and detected one population with predominance of sexual reproduction. DAPC analysis pointed the formation of three groups, which corresponded to the populations analyzed. The markers were successfully amplified in related species, with some species presenting 80% transferability. By producing this panel of polymorphic microsatellites, we contribute to the understanding evolution in groups of natural polyploids for future studies.

Stomatal size, ploidy and polyembryony in Eriotheca Stellate Trichome Species Complex (Bombacoideae - Malvaceae) in the Cerrados of Brazil.

Geographic parthenogenesis, range expansion of apomictic plants after climate changes, has been described for Northern Hemisphere gametophytic apomicts. But similar trends have been observed for sporophytic apomicts of Cerrado, the savannas in Brazil. Eriotheca pubescens is a common Cerrado tree, an agamic complex of either hexaploid/polyembryonic apomicts or tetraploid/monoembryonic sexual individuals. Some populations have been described as a new species, Eriotheca estevesiae, all included in the Eriotheca Stellate Trichome Species Complex (ESTSC). Since breeding systems and ploidy are clearly associated with polyembryony and stomatal size, we used these ancillary features to map the reproductive and ploidy level traits of E. pubescens and E. estevesiae. Leaves and seeds were collected from individuals of 19 populations. Seeds were evaluated for the presence of polyembryony and leaves for stomatal measurements. Eight populations were monoembryonic while another eight were polyembryonic and for other three, the embryonic pattern was not readily verified. E. pubescens polyembryonic and hexaploid populations formed a homogeneous group, but monoembryonic plants were more variable. E. estevesiae populations were monoembryonic with smaller stomata. In contrast, some E. pubescens monoembryonic populations further south presented larger stomata. Despite these outliers, possibly mixed populations, stomatal size and embryonic pattern differed from northern to southern populations. Embryonic pattern and stomatal size indicated that northernmost populations of Eriotheca STSC (E. estevesiae) are diploid and sexual. Southernmost populations, mostly polyembryonic and with large stomata, are hexaploid and apomictic. This is in agreement with geographic parthenogenesis and range expansion of apomictic lineages to southern habitats available after the last glacial maximum.

The genetic basis of oral leukoplakia and its key role in understanding oral carcinogenesis.

Oral leukoplakia (OL) is the most common oral potentially malignant disorder, with a global prevalence of 2%-3%, variable malignant transformation rate and incompletely understood aetiology. Considering the subjectivity in oral dysplasia grading, other evaluation methods have been tested as predictors of malignant transformation. DNA ploidy status and loss of heterozygosity signatures have been shown to be good predictive markers of malignant transformation. However, effective markers to predict which lesions will progress to invasive carcinoma and by which mechanisms remain unclear. Recent evidence suggests that dysplasia progression to carcinoma occurs through neutral clonal evolution (i.e. randomly). We focus on the genetic basis of OL, encompassing the gross chromosomal alterations and single-gene mutations, and discuss such alterations in the context of aetiology, clinical presentation and progression. The deeper we understand the genetic basis of OL, the more we approach a better comprehension of the complex and poorly understood process of oral carcinogenesis.

Evidence of hybridization, mitochondrial introgression and biparental inheritance of the kDNA minicircles in Trypanosoma cruzi I.

BACKGROUND: Genetic exchange in Trypanosoma cruzi is controversial not only in relation to its frequency, but also to its mechanism. Parasexual genetic exchange has been proposed based on laboratory hybrids, but population genomics strongly suggests meiosis in T. cruzi. In addition, mitochondrial introgression has been reported several times in natural isolates although its mechanism is not fully understood yet. Moreover, hybrid T. cruzi DTUs (TcV and TcVI) have inherited at least part of the kinetoplastic DNA (kDNA = mitochondrial DNA) from both parents. METHODOLOGY/PRINCIPAL FINDINGS: In order to address such topics, we sequenced and analyzed fourteen nuclear DNA fragments and three kDNA maxicircle genes in three TcI stocks which are natural clones potentially involved in events of genetic exchange. We also deep-sequenced (a total of 6,146,686 paired-end reads) the minicircle hypervariable region (mHVR) of the kDNA in such three strains. In addition, we analyzed the DNA content by flow cytometry to address cell ploidy. We observed that most polymorphic sites in nuclear loci showed a hybrid pattern in one cloned strain and the other two cloned strains were compatible as parental strains (or nearly related to the true parents). The three clones had almost the same ploidy and the DNA content was similar to the reference strain Sylvio (a nearly diploid strain). Despite maxicircle genes evolve faster than nuclear housekeeping ones, we detected no polymorphisms in the sequence of three maxicircle genes showing mito-nuclear discordance. Lastly, the hybrid stock shared 66% of its mHVR clusters with one putative parent and 47% with the other one; in contrast, the putative parental stocks shared less than 30% of the mHVR clusters between them. CONCLUSIONS/SIGNIFICANCE: The results suggest a reductive division, a natural hybridization, biparental inheritance of the minicircles in the hybrid and maxicircle introgression. The models including such phenomena and explaining the relationships between these three clones are discussed.

Genomic analyses reveal moderate levels of ploidy, high heterozygosity and structural variations in a Colombian isolate of Leishmania (Leishmania) amazonensis.

Leishmania amazonensis is one of the causative agents of the different forms of cutaneous leishmaniasis present in Latin America. This species has been isolated from humans and animals (canine/feline) in some endemic regions of Colombia. Therefore, L. amazonensis is of great relevance at the clinical and epidemiological levels in medicine and veterinary science. Until now, very few genomes from this species are available. Here, we report the complete genome sequence of a laboratory-adapted L. amazonensis strain isolated from a human patient with clinical manifestation of cutaneous leishmaniasis in Colombia. The genome sequence not only allowed inter and intra-species comparative analyses to be performed with the sequenced genomes of L. amazonensis strains from different geographical regions, but also increased our knowledge about the genomic behavior of this L. amazonensis Colombian strain. This isolate was also characterized in terms of single nucleotide polymorphisms, chromosome and gene copy number variations (CNVs). The results revealed moderate aneuploidy, CNVs in genes involved in the virulence, growth, and survival of the parasite, and in the distributions of the multicopy genes on some chromosomes, as well as a high level of heterozygosity. The data confirmed previous reports that identified unique variations in L. amazonensis, suggesting aneuploidy may not have a high fitness cost and may allow the rapid generation of diversity in Leishmania parasites growing normally.

Comparative karyotype analysis among cytotypes of Cynodon dactylon (L.) Pers. (Poaceae).

Cynodon dactylon is characterized by taxonomic and systematic complexity, and polyploidy is one of the factors responsible for its genetic and morphological diversity. The aim of the present study was to compare karyotypes of C. dactylon cytotypes based on fluorescent banding and nuclear DNA content. The nine C. dactylon accessions evaluated were obtained from the Active Germplasm Bank (BAG) of the United States Department of Agriculture (USDA). Roots were pretreated with cycloheximide, fixed in Carnoy's solution and subjected to enzymatic digestion. Slides were prepared by the dissociation and air-drying technique. The fluorescent banding pattern was obtained using chromomycin A3 (CMA)/4,6-dimidino-2-phenylindole (DAPI) staining and DNA content was estimated by flow cytometry. The chromosome number of the accessions ranged from 2n = 2x = 18 to 2n = 5x = 45. Chromosomal polymorphism was observed based on the distribution and number of heterochromatic bands, with CMA+ bands located in the pericentromeric position and DAPI+ bands mainly in the terminal position. PI477004-26 (2n = 3x = 27) and PI291966-27 (2n = 4x = 36) had the highest and lowest number of DAPI+ bands, respectively. The number of CMA+ bands was stable, as only PI477004-26, PI291966-27 and PI289750-10 (2n = 5x = 45) showed variation. There was no direct correlation between an increase in the ploidy level and an increase in the percentage of heterochromatic regions, mainly in relation to A-T-rich blocks. The chromosomal banding variation found reinforces the notion of allopolyploidy occurrence in C. dactylon and demonstrates the genomic complexity of this species regard to repetitive DNA content.

All Eukaryotes Are Sexual, unless Proven Otherwise: Many So-Called Asexuals Present Meiotic Machinery and Might Be Able to Have Sex.

Here a wide distribution of meiotic machinery is shown, indicating the occurrence of sexual processes in all major eukaryotic groups, without exceptions, including the putative "asexuals." Meiotic machinery has evolved from archaeal DNA repair machinery by means of ancestral gene duplications. Sex is very conserved and widespread in eukaryotes, even though its evolutionary importance is still a matter of debate. The main processes in sex are plasmogamy, followed by karyogamy and meiosis. Meiosis is fundamentally a chromosomal process, which implies recombination and ploidy reduction. Several eukaryotic lineages are proposed to be asexual because their sexual processes are never observed, but presumed asexuality correlates with lack of study. The authors stress the complete lack of meiotic proteins in nucleomorphs and their almost complete loss in the fungus Malassezia. Inversely, complete sets of meiotic proteins are present in fungal groups Glomeromycotina, Trichophyton, and Cryptococcus. Endosymbiont Perkinsela and endoparasitic Microsporidia also present meiotic proteins.

Low-copy nuclear sequence data confirm complex patterns of farina evolution in notholaenid ferns (Pteridaceae).

Notholaenids are an unusual group of ferns that have adapted to, and diversified within, the deserts of Mexico and the southwestern United States. With approximately 40 species, this group is noted for being desiccation-tolerant and having "farina"-powdery exudates of lipophilic flavonoid aglycones-that occur on both the gametophytic and sporophytic phases of their life cycle. The most recent circumscription of notholaenids based on plastid markers surprisingly suggests that several morphological characters, including the expression of farina, are homoplasious. In a striking case of convergence, Notholaena standleyi appears to be distantly related to core Notholaena, with several taxa not before associated with Notholaena nested between them. Such conflicts can be due to morphological homoplasy resulting from adaptive convergence or, alternatively, the plastid phylogeny itself might be misleading, diverging from the true species tree due to incomplete lineage sorting, hybridization, or other factors. In this study, we present a species phylogeny for notholaenid ferns, using four low-copy nuclear loci and concatenated data from three plastid loci. A total of 61 individuals (49 notholaenids and 12 outgroup taxa) were sampled, including 31 out of 37 recognized notholaenid species. The homeologous/allelic nuclear sequences were retrieved using PacBio sequencing and the PURC bioinformatics pipeline. Each dataset was first analyzed individually using maximum likelihood and Bayesian inference, and the species phylogeny was inferred using *BEAST. Although we observed several incongruences between the nuclear and plastid phylogenies, our principal results are broadly congruent with previous inferences based on plastid data. By mapping the presence of farina and their biochemical constitutions on our consensus phylogenetic tree, we confirmed that the characters are indeed homoplastic and have complex evolutionary histories. Hybridization among recognized species of the notholaenid clade appears to be relatively rare compared to that observed in other well-studied fern genera.