Triploid Hybrids Research Articles

Novel genetic variants of banana streak MY virus and banana streak IM virus naturally infecting banana in Northeast India.

Divergent banana streak viruses (BSV) were characterized from banana plants exhibiting diverse symptoms in the Northeast region (NER) of India. Using rolling circle amplification (RCA), the complete genome sequences of seven episomal banana streak MY virus (BSMYV) isolates, including two novel variants, and two new banana streak IM virus (BSIMV) isolates were characterized. The novel BSMYV genetic variants were associated with conspicuous necrosis on newly emerged leaves, peduncle distortion, pseudostem internal necrosis, in addition to common streak symptoms. For complete genome nucleotide sequences, BSMYV-IN4 and IN5 shared 77-79% identity with other BSMYVs, while BSMYV-IN7 and IN8 exhibited identities of 77-97%. This study reports for the first time, the complete genomes of two banana streak IM virus (BSIMV-IN1 and -IN2) infecting triploid banana hybrids exhibiting leaf distortion, stunted rosette-like growth, and necrosis, sharing 87% sequence identity with reference BSIMV genome (GenBank accession no. HQ593112). Phylogenetic inference based on complete genomes revealed the distinct and congruent placement of BSMYV-IN4 and IN5 within the BSMYV cluster. Pairwise sequence comparisons of the conserved RT/RNase H nucleotide (nt) sequences revealed that the BSMYV-IN7 and IN4 isolates showed 85% and 97% identity to BSMYV (AY805074), respectively, which shared highest nt identity with BSMYV-IN6, IN9, and IN10, at 100%. The RT/RNase H nt sequences of BSIMV-IN1 and IN2 had 98% identity with the BSIMV (HQ593112), but were characterized as novel variants of BSIMV based on complete genomes. An analysis of relative synonymous codon usage (RSCU) pattern in the ORFIII polyprotein of BSMYV and BSIMV isolates revealed AGA and AGG (arginine) as the most frequently overrepresented codons (>1.5), evolutionary conserved in the genome of both species. A total of 14 recombination events were detected among the 36 BSV genomes, with recombination breakpoints mainly located in the ORFI, III, and IGR genomic regions. A novel phylogenetic cluster, comprised of BSMYV-IN4 and IN5 within the clade I was probably derived from heterologous recombination between parents resembling banana streak VN virus (BSVNV; AY750155) and banana streak GF virus (BSGFV; KJ013507) isolates. The present study conclusively reports the infection of genetically and symptomatically distinct variants of BSMYV and BSIMV infecting banana hybrids in NER India.

Endogenous viral elements are targeted by RNA silencing pathways in banana.

Endogenous banana streak virus (eBSV) integrants derived from three distinct species, present in Musa balbisiana (B) but not Musa acuminata (A) banana genomes are able to reconstitute functional episomal viruses causing banana streak disease in interspecific triploid AAB banana hybrids but not in the diploid (BB) parent line, which harbours identical eBSV loci. Here, we investigated the regulation of these eBSV. In-depth characterization of siRNAs, transcripts and methylation derived from eBSV using Illumina and bisulfite sequencing were carried out on eBSV-free Musa acuminata AAA plants and BB or AAB banana plants with eBSV. eBSV loci produce low-abundance transcripts covering most of the viral sequence and generate predominantly 24-nt siRNAs. siRNA accumulation is restricted to duplicated and inverted viral sequences present in eBSV. Both siRNA-accumulating and nonaccumulating sequences of eBSV in BB plants are heavily methylated in all three CG, CHG and CHH contexts. Our data suggest that eBSVs are controlled at the epigenetic level in BB diploids. This regulation not only prevents their awakening and systemic infection of the plant but is also probably involved in the inherent resistance of the BB plants to mealybug-transmitted viral infection. These findings are thus of relevance to other plant resources hosting integrated viruses.

The osteology of the lacertid genus Darevskia Arribas, 1999 (Squamata, Lacertidae)

A total of 230 cleared and alizarin stained and 136 radiographed specimens of Darevskia belonging to 47 nominal taxa (species, subspecies or singular clades) including the seven parthenogenetic ones and a triploid hybrid were studied. Sixteen osteological characters in all the tried species were analyzed. These characters by corporal regions were: skull characters: 1.—number of premaxillary teeth; 2.—number of maxillary teeth; 3.—number of dentary teeth; 4.—teeth morphology; 5.—presence of anterolateral process in the postfrontal bone; 6.—presence of anteromedial process in the postorbital bone; 7.—comparative lengths of the postorbital and postfrontal bones; 8.—overlap degree between the postorbital and the squamosal bones. Postcranial characters: 9.—existence of visible (ossified) ribs associated with the third presacral vertebrae; 10.—sternal/xiphisternal costal formula and presence of inscriptional ribs; 11.—number of presacral vertebrae; 12.—number of posterior dorsal vertebrae (short presacral ribs); 13.—presence and form of the sternal fontanelle; 14.—form of the clavicles (emarginated or marginated); 15.—interclavicle form; 16.—morphology of first autotomic vertebrae of the tail. Our goals were to characterize osteologically the different species of Darevskia, to contrast their relationships traced from osteological traits with the available genetic-derived phylogenies of the group, to compare the osteological characteristics of the parthenogenetic species with their bisexual parental species, and to comment on their parentage and character polarity. Finally, we aimed to search for osteological characteristics of the different groups within Darevskia, diagnosing them for the first time. The results, commented on by characters, are available in the main text, and taxa characteristics are easily consultable and condensed in Table 1. Osteological characteristics of Darevskia, together with available phylogenetic trees, have permitted us to define some new groups within Darevskia (raddei, chlorogaster, defilippi, and parvula new groups) (Appendix 3), which are reciprocally monophyletic and have diagnostic characteristics. All of them are diagnosed and named as subgenera to be used if necessary, instead of the partial, old and not always comprehensive groups.

UBE2J1 suppresses interferon signaling by facilitating the ubiquitination and degradation of IRF7

Ubiquitin-binding enzyme E2J1 (UBE2J1) is a predominant member of the UBE2 family. In mammals, it is involved in antiviral immunity, ER-misfolded protein degradation, and ubiquitination. However, the function of UBE2J1 in teleost has not been elucidated. In the present study, we cloned the homolog of UBE2J1 in triploid hybrid fish and investigated its regulatory role in the antiviral interferon (IFN) signaling. We determined that the full-length coding sequence of the triploid fish UBE2J1 (3nUBE2J1) consists of 939 base pairs and encodes 313 amino acids. Upon SVCV infection, the mRNA levels of 3nUBE2J1 were increased in the spleen, liver, kidney, and the caudal fin cell line of triploid fish. Knockdown of 3nUBE2J1 in host cells and fish enhanced their antiviral response and curtailed SVCV replication. Conversely, overexpression of 3nUBE2J1 inhibited the activation of IFN promoter induced by SVCV, poly (I:C), or RLR pathway factors. Further studies revealed that 3nUBE2J1 interacted with 3nIRF7 and suppressed both the protein level and antiviral activity of 3nIRF7. Finally, we demonstrated that 3nUBE2J1 enhanced the K27- and K29-linked ubiquitination of 3nIRF7, leading to its degradation. Collectively, our findings indicate that triploid fish UBE2J1 serves as a novel negative regulator of IFN signaling by inhibiting 3nIRF7.

Tolerance of Triploid Hybrids of White Poplar ‘Beilinxiongzhu 1’ to Genetic Transformation Screening Agents In Vitro

Genetic transformation of forest trees is essential for validating gene functions and breeding new varieties through molecular means. Appropriate selective pressure is critical for creating an effective screening system. ‘Beilinxiongzhu 1’ sensitivity testing showed that the critical tolerance concentrations for hygromycin (Hyg), kanamycin (Kan), and glyphosate (PPT) in leaf explants were 2.0 mg/L, 20 mg/L, and 1.0 mg/L, respectively. Among the physiological indicators, soluble sugar content, soluble protein content, and endogenous hormone levels were identified as key markers of the effects of the different antibiotic treatments. Transcriptome analysis showed that Hyg treatment resulted in a large number of differentially expressed genes (DEGs) involved in leaf cell wall synthesis and glucose metabolism. Under Kan treatment, the DEGs were associated with pathways such as ribosome biosynthesis and histone packaging in eukaryotes. Under PPT treatment, significant DEGs were related to ABC transporters. DEGs common to all three antibiotics were involved in glutathione metabolism pathways. A weighted gene co-expression network analysis identified TRXH2, H3.2, H2B, GST, U71K1, and CHS as key genes in response to antibiotic stress. By elucidating the physiological and molecular mechanisms by which different antibiotics affect leaf sprouting, our study serves as a reference for research into the genetic transformation of poplar leaves.

Asexuality shapes traits in a hybrid fish

Animal morphology is influenced by several factors, including gonadal development and gametogenesis. Although their effects are well documented in male/female differentiation, much less is known about same-sex effects, such as those caused by their mode of reproduction. Here, using geometric morphometric analyses, we compare two groups of all-female triploid hybrid fish Chrosomus eos × eos-neogaeus, that differ only by their sexual and asexual reproductive strategies. We demonstrate that morphological differences arise from factors inherently associated with their mode of reproduction, with results replicated in two distinct lineages and in natural and common garden environments. Such differences provide additional insight about the costs and benefits of both reproductive strategies, which have mostly been of a demographic, population genetic, or genetic nature. In particular, these findings have important implications for the ecology of asexual organisms and contribute to the study of sex evolution by adding complexity to the paradox of sex theory.

Towards the conservation of the crucian carp in Europe: Prolific hybridization but no evidence for introgression between native and non-native taxa.

Hybridization plays a pivotal role in evolution, influencing local adaptation and speciation. However, it can also reduce biodiversity, which is especially damaging when native and non-native species meet. Hybridization can threaten native species via competition (with vigorous hybrids), reproductive resource wastage and gene introgression. The latter, in particular, could result in increased fitness in invasive species, decreased fitness of natives and compromise reintroduction or recovery conservation practices. In this study, we use a combination of RAD sequencing and microsatellites for a range-wide sample set of 1366 fish to evaluate the potential for hybridization and introgression between native crucian carp (Carassius carassius) and three non-native taxa (Carassius auratus auratus, Carassius auratus gibelio and Cyprinus carpio) in European water bodies. We found hybridization between native and non-native taxa in 82% of populations with non-natives present, highlighting the potential for substantial ecological impacts from hybrids on crucian carp populations. However, despite such high rates of hybridization, we could find no evidence of introgression between these taxa. The presence of triploid backcrosses in at least two populations suggests that the lack of introgression among these taxa is likely due to meiotic dysfunction in hybrids, leading to the production of polyploid offspring which are unable to reproduce sexually. This result is promising for crucian reintroduction programs, as it implies limited risk to the genetic integrity of source populations. Future research should investigate the reproductive potential of triploid hybrids and the ecological pressures hybrids impose on C. carassius.

Comparative histological analysis of gonad development between autotriploid (Crassostrea gigas and C. angulata) and allotriploid oysters

China has the highest oyster yield in the world, with Crassostrea gigas and C. angulata being the two most productive oysters species. The hybrid triploid of Crassostrea gigas and C. angulata exhibits good heat resistance and can mitigate the plight of mass mortality of Crassostrea gigas in northern China caused by high temperature and spawning during the summer. Additionally, triploid oysters have reduced fecundity, which allows the energy typically used for gonad development to be redirected to somatic cell growth, resulting in better taste and lower mortality during the reproductive season. Therefore, it is essential to study the detailed gonad development of hybrid triploid oysters. This study compared the gonad development between autotriploids (TGG-diploid C. gigas ♀ × tetraploid C. gigas ♂) and allotriploids (TAG-diploid C. angulata ♀ × tetraploid C. gigas ♂) during the breeding season. Results showed that the female proportion of TGG increased gradually with rising temperature, reaching a peak of 57.1% in August, whereas the proportion of females in TAG was lower, with males accounting for >50% from June to August 2023. Histological analysis revealed that the proportion of female α (producing many oocytes) increased with gonad development, peaking for TGG female α in July and for TAG female α in September. Moreover, the number of sperm in male TAG gonadal tubules was less than in male TGG, and more apoptotic cells were observed in the ultrastructure of male TAG gonad, which was confirmed by apoptosis experiment. Based on these results, it is suggested that the gonad development of female and hermaphrodite TAG were delayed compared with TGG, and the level of sterility in male TAG should be higher than in male TGG.

Selective autophagy receptor p62/SQSTM1 inhibits TBK1-IRF7 innate immune pathway in triploid hybrid fish

The production of type I interferon is tightly regulated to prevent excessive immune activation. However, the role of selective autophagy receptor SQSTM1 in this regulation in teleost remains unknown. In this study, we cloned the triploid fish SQSTM1 (3nSQSTM1), which comprises 1371 nucleotides, encoding 457 amino acids. qRT-PCR data revealed that the transcript levels of SQSTM1 in triploid fish were increased both in vivo and in vitro following spring viraemia of carp virus (SVCV) infection. Immunofluorescence analysis confirmed that 3nSQSTM1 was mainly distributed in the cytoplasm. Luciferase reporter assay results showed that 3nSQSTM1 significantly blocked the activation of interferon promoters induced by 3nMDA5, 3nMAVS, 3nTBK1, and 3nIRF7. Co-immunoprecipitation assays further confirmed that 3nSQSTM1 could interact with both 3nTBK1 and 3nIRF7. Moreover, upon co-transfection, 3nSQSTM1 significantly inhibited the antiviral activity mediated by TBK1 and IRF7. Mechanistically, 3nSQSTM1 decreased the TBK1 phosphorylation and its interaction with 3nIRF7, thereby suppressing the subsequent antiviral response. Notably, we discovered that 3nSQSTM1 also interacted with SVCV N and P proteins, and these viral proteins may exploit 3nSQSTM1 to further limit the host's antiviral innate immune responses. In conclusion, our study demonstrates that 3nSQSTM1 plays a pivotal role in negatively regulating the interferon signaling pathway by targeting 3nTBK1 and 3nIRF7.

Different ploidy-level hybrids derived from female common carp × male topmouth culter

Distant hybridization is an effective strategy for creating polyploids in fish genetic breeding. In this study, the cross of common carp (Cyprinus carpio, 2n = 100, COC, ♀) and topmouth culter (Culter alburnus, 2n = 48, TC, ♂), which belonged to different subfamilies, was conducted and obtained surviving hybrid offspring (CT hybrids). Based on the measurement of DNA content and chromosomal numbers, three ploidy levels of CT hybrids were identified: diploid hybrids (2n = 74, 2nCT), triploid hybrids (3n = 124, 3nCT), and tetraploid hybrids (4n = 148, 4nCT). Analyses of countable traits and measurable traits indicated a significant similarity between CT hybrids and COC in comparison to TC. The genetic variation analysis of 5S rDNA and HoxD10a gene in CT hybrids revealed the retention of all COC genotypes and the partial elimination of TC genotypes, as well as the generation of novel variant genotypes (derived from TC genotypes) and recombinant genotypes (derived from parental genotypes), which suggested that in CT hybrids, the paternal subgenome exhibited greater instability than the maternal subgenome. In addition, the droplet digital PCR (ddPCR) method, combining allele-specific probes targeting the EPHX2 gene, was employed for the first time to investigate the genome composition of hybrids. The results showed that the ratios of COC-allele number to TC-allele number were approximately 1 in 2nCT, 2 in 3nCT, and 1.5 in 4nCT, respectively, which confirmed the hybridization origins for each type and effectively distinguished between the three CT hybrids. The obtainment of CT hybrids harbors potential benefits and application in aquaculture and provides an ideal model for understanding the influence of hybridization and polyploidization on the genomic composition of fish species.

Hybridization and introgression in deeply differentiated salamander species – molecular genetics and a reappraisal of Dr. Louis Vallée’s osteological data

Abstract Two morphologically and genetically distinct salamander species (the crested newt, Triturus cristatus and the marbled newt, T. marmoratus) engage over a large area in the west of France where they hybridize at ca. 4%. The species interaction is characterized by ecological differentiation and limited gene flow beyond the F1 hybrid generation. Incompletely isolated species like these allow to investigate the genetic mechanisms and evolutionary forces that maintain their identity in the face of ongoing gene flow, to which a large mosaic hybrid zone provides excellent opportunities. A reanalysis of published morphological data supports the partial breakdown of the species barrier whereas extensive genetic data show that introgression is low yet asymmetric, in line with the dynamics of species replacement inferred earlier. The current work, with seven diagnostic nuclear markers studied for a large sample, revises the estimates of introgression in both T. cristatus (to 0.24%) and T. marmoratus (to 0.11%). Difficulties remain in the recognition of potential triploid hybrids versus backcross hybrids. Haldane’s rule is partially supported, but deeper analyses require the use of a molecular marker for sex that is not yet available.

Love bites: males of lizards prefer to mate with conspecifics, but do not disdain parthenogens

Abstract Parthenogenesis has been discovered in a great number of reptiles, indicating that parthenogens can outcompete bisexual species and hybridize with them. This raises intriguing questions: how do parthenogenetic species coexist with gonochoristic relatives, and what outcome does this coexistence produce? To answer these two questions, we studied relationships between male rock lizards, Darevskia valentini, and parthenogenetic Darevskia armeniaca. We compared social and sexual reactions of males to females of their own species and parthenogenetic D. armeniaca and vice versa. We found that females of both species basked together with males and demonstrated mostly submissive behaviour. Females of D. valentini were less aggressive towards males in the mixed-species population than in the single-species population, suggesting female competition for males. The proportion of successful and unsuccessful mating attempts with females of bisexual and unisexual species was equal, and we found no significant differences in male reactions to bisexual and unisexual females in sympatry. The proportion of females bearing mating scars on their venters and the number of these scars per female were greater in the bisexual species. This indicates that females of the bisexual species were more attractive than parthenogenetic females as mating partners to males. We found no triploid hybrids among the offspring of parthenogenetic females that mated with males in the mixed population. Our findings suggest that parthenogenetic species might outcompete bisexual species by mating with males and integrating into the social system.

Biomass yields, reproductive fertility, compositional analysis, and genetic diversity of newly developed triploid giant miscanthus hybrids

AbstractMiscanthus ×giganteus (giant miscanthus), first found as a naturally occurring hybrid, has shown promise as a bioenergy/biomass crop throughout much of the temperate world. This allotriploid (2n = 3x = 57) hybrid resulted from a cross between tetraploid Miscanthus sacchariflorus (2n = 4x = 76) and diploid Miscanthus sinensis (2n = 2x = 38) and is particularly desirable due to its low fertility that minimizes reseeding and potential invasiveness. However, there is limited genetic diversity in commonly grown cultivars of triploid M. ×giganteus and breeding and development efforts to improve and domesticate this crop have been minimal. Here, we report on newly developed M. ×giganteus hybrids compared with the industry standard M. ×giganteus '1993‐1780'. Dry biomass yields of new hybrids ranged from 19.5 to 32.4 Mg/ha/year for the fourth growing season, compared with 21.0 Mg/ha/year for M. ×giganteus '1993‐1780'. Plant reproductive fertility remained low for all accessions with overall fertility [(seed set × seed germination)/100] ranging from 0.3% to 4.5% for new hybrids compared to 0.4% for M. ×giganteus '1993‐1780'. Culm density and height varied among accessions and were positively correlated with increased biomass. Based on compositional analyses, theoretical ethanol yields ranged from 9, 740 to 16,278 L/ha/year for new hybrids compared to 10,406 L/ha/year for M. ×giganteus '1993‐1780'. Relative feed value indices were low overall and ranged between 66.0 and 72.8 for new hybrids compared to M. ×giganteus '1993‐1780' with 71.3. The genetic diversity of new hybrids, compared with existing cultivars, was characterized using whole genome sequences. Based on pair‐wise distances, cluster analysis clearly showed increased diversity of new hybrids compared with earlier selections. These results document new triploid hybrids of M. ×giganteus with enhanced biomass and theoretical ethanol yields in combination with broader genetic diversity and lowreproductive fertility.

Multiple hybridization events and repeated evolution of homoeologue expression bias in parthenogenetic, polyploid New Zealand stick insects.

During hybrid speciation, homoeologues combine in a single genome. Homoeologue expression bias (HEB) occurs when one homoeologue has higher gene expression than another. HEB has been well characterized in plants but rarely investigated in animals, especially invertebrates. Consequently, we have little idea as to the role that HEB plays in allopolyploid invertebrate genomes. If HEB is constrained by features of the parental genomes, then we predict repeated evolution of similar HEB patterns among hybrid genomes formed from the same parental lineages. To address this, we reconstructed the history of hybridization between the New Zealand stick insect genera Acanthoxyla and Clitarchus using a high-quality genome assembly from Clitarchus hookeri to call variants and phase alleles. These analyses revealed the formation of three independent diploid and triploid hybrid lineages between these genera. RNA sequencing revealed a similar magnitude and direction of HEB among these hybrid lineages, and we observed that many enriched functions and pathways were also shared among lineages, consistent with repeated evolution due to parental genome constraints. In most hybrid lineages, a slight majority of the genes involved in mitochondrial function showed HEB towards the maternal homoeologues, consistent with only weak effects of mitonuclear incompatibility. We also observed a proteasome functional enrichment in most lineages and hypothesize this may result from the need to maintain proteostasis in hybrid genomes. Reference bias was a pervasive problem, and we caution against relying on HEB estimates from a single parental reference genome.

Chromosome stability of synthetic Triticum turgidum–Aegilops umbellulata hybrids

BackgroundUnreduced gamete formation during meiosis plays a critical role in natural polyploidization. However, the unreduced gamete formation mechanisms in Triticum turgidum–Aegilops umbellulata triploid F1 hybrid crosses and the chromsome numbers and compostions in T. turgidum–Ae. umbellulata F2 still not known.ResultsIn this study, 11 T.turgidum–Ae. umbellulata triploid F1 hybrid crosses were produced by distant hybridization. All of the triploid F1 hybrids had 21 chromosomes and two basic pathways of meiotic restitution, namely first-division restitution (FDR) and single-division meiosis (SDM). Only FDR was found in six of the 11 crosses, while both FDR and SDM occurred in the remaining five crosses. The chromosome numbers in the 127 selfed F2 seeds from the triploid F1 hybrid plants of 10 crosses (no F2 seeds for STU 16) varied from 35 to 43, and the proportions of euploid and aneuploid F2 plants were 49.61% and 50.39%, respectively. In the aneuploid F2 plants, the frequency of chromosome loss/gain varied among genomes. The chromosome loss of the U genome was the highest (26.77%) among the three genomes, followed by that of the B (22.83%) and A (11.81%) genomes, and the chromosome gain for the A, B, and U genomes was 3.94%, 3.94%, and 1.57%, respectively. Of the 21 chromosomes, 7U (16.54%), 5 A (3.94%), and 1B (9.45%) had the highest loss frequency among the U, A, and B genomes. In addition to chromosome loss, seven chromosomes, namely 1 A, 3 A, 5 A, 6 A, 1B, 1U, and 6U, were gained in the aneuploids.ConclusionIn the aneuploid F2 plants, the frequency of chromosome loss/gain varied among genomes, chromsomes, and crosses. In addition to variations in chromosome numbers, three types of chromosome translocations including 3UL·2AS, 6UL·1AL, and 4US·6AL were identified in the F2 plants. Furthermore, polymorphic fluorescence in situ hybridization karyotypes for all the U chromosomes were also identified in the F2 plants when compared with the Ae. umbellulata parents. These results provide useful information for our understanding the naturally occurred T. turgidum–Ae. umbellulata amphidiploids.

Discovery of natural Paspalum L. (Poaceae) triploid hybrids near sympatric populations of Paspalum urvillei Steud. and species of Paniculata group in northeastern Argentina

Discovery of natural Paspalum L. (Poaceae) triploid hybrids near sympatric populations of Paspalum urvillei Steud. and species of Paniculata group in northeastern Argentina

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.

GSTP1 is a negative regulator of MAVS in the antiviral signaling against SVCV infection

Glutathione S-transferase P1 (GSTP1), the most ubiquitous member of the GST superfamily, plays vital roles in the detoxification, antioxidant defense, and modulation of inflammatory responses. However, limited studies have been conducted on the function of GSTP1 in antiviral innate immunity. In this study, we have cloned the homolog of GSTP1 in triploid hybrid crucian carp (3nGSTP1) and investigated its regulatory role in the interferon signaling pathway. The open reading frame of 3nGSTP1 is composed of 627 nucleotides, encoding 209 amino acids. In response to spring viremia of carp virus (SVCV) infection, the mRNA level of 3nGSTP1 was up-regulated in the liver, kidney, and caudal fin cell lines (3 nF C) of triploid fish. The knockdown of 3nGSTP1 in 3 nF C improved host cell's antiviral capacity and attenuated SVCV replication. Additionally, overexpression of 3nGSTP1 inhibited the activation of IFN promoters induced by SVCV infection, poly (I:C) stimulation, or the RLR signaling factors. The co-immunoprecipitation assays further revealed that 3nGSTP1 interacts with 3nMAVS. In addition, 3nGSTP1 dose-dependently inhibited 3nMAVS-mediated antiviral activity and reduced 3nMAVS protein level. Mechanistically, 3nGSTP1 promoted ubiquitin-proteasome degradation of MAVS by promoting its K48-linked polyubiquitination. To conclude, our results indicate that GSTP1 acts as a novel inhibitor of MAVS, which negatively regulates the IFN signaling.

Inheritance pattern of tetraploids pummelo, mandarin, and their interspecific hybrid sour orange is highly influenced by their phylogenomic structure.

Citrus polyploidy is associated with a wide range of morphological, genetic, and physiological changes that are often advantageous for breeding. Citrus triploid hybrids are very interesting as new seedless varieties. However, tetraploid rootstocks promote adaptation to different abiotic stresses and promote resilience. Triploid and tetraploid hybrids can be obtained through sexual hybridizations using tetraploid parents (2x × 4x, 4x × 2x, or 4x × 4x), but more knowledge is needed about the inheritance pattern of tetraploid parents to optimize the efficiency of triploid varieties and tetraploid rootstock breeding strategies. In this work, we have analyzed the inheritance pattern of three tetraploid genotypes: 'Chandler' pummelo (Citrus maxima) and 'Cleopatra' mandarin (Citrus reticulata), which represent two clear examples of autotetraploid plants constituted by the genome of a single species, and the 'Sevillano' sour orange, which is an allotetraploid interspecific hybrid between C. maxima and C. reticulata. Polymorphic simple sequence repeat (SSR) and single-nucleotide polymorphism (SNP) markers were used to estimate parental heterozygosity restitution, and allele frequencies for centromeric loci were used to calculate the preferential pairing rate related to the proportion of disomic and tetrasomic segregation. The tetraploid pummelo and mandarin displayed tetrasomic segregation. Sour orange evidenced a clear intermediate inheritance for five of the nine chromosomes (1, 2, 5, 7, and 8), a slight tendency toward tetrasomic inheritance on chromosome 3, and intermediate inheritance with a tendency toward disomy for chromosomes 4, 6, and 9. These results indicate that the interspecific versus intraspecific phylogenomic origin affects preferential pairing and, therefore, the inheritance patterns. Despite its high level of heterozygosity, the important preferential chromosome pairing observed in sour orange results in a limited diversity of the genotypic variability of its diploid gametes, and consequently, a large part of the genetic value of the original diploid sour orange is transferred to the tetraploid progenies.

Triploid Hybrids of 2x Lingonberry (Vaccinium vitis-idaea) by 2x Black Highbush Blueberry (V. fuscatum) and 2x Elliott’s Blueberry (V. elliottii) as Evidence of a Genome Balance Requirement for Hybridization Success

Hybridizations were made between a 2x V. vitis-idaea (sect. Vitis-idaea, lingonberry) and 2x V. fuscatum (sect. Cyanococcus, Black Highbush Blueberry) as part of a project aimed at understanding the crossability and compatibility of these but specifically aimed at assessing the possibilities for improvement and utilization of lingonberry. The crosses succeeded at a low level, and six hybrids were produced and genetically verified. When tested for ploidy level, five of the six hybrids were found to be triploids and one was found to be a tetraploid. Hybrids were intermediate in morphology and only fertile at very low levels, largely due to their triploid nature. Several of these hybrids produced progeny when used as females and pollinated with 6x V. virgatum-derived males, indicating viable unreduced 2n ovules. Similar crosses were made between lingonberry and 2x V. elliottii (sect. Cyanococcus, Elliott’s Blueberry). These crosses produced two genetically verified hybrids, which were also determined to be triploids. These hybrids were effectively sterile. The production of triploids from 2x × 2x crosses indicates that there is a natural selection for a reproductive genome balance of two V. vitis-idaea:one Cyanococcus. The success of secondary hybridizations with hexaploid materials suggests that the triploid hybrids may be used to advance the utilization and recombination of lingonberry germplasm.