Genomic and Meiotic Changes Accompanying Polyploidization

The synaptonemal complex stabilizes meiosis in allotetraploid Brassica napus and autotetraploid Arabidopsis thaliana

Polyploidy plays a key role in genome evolution and crop improvement. The formation of bivalents rather than multivalents during meiosis of polyploids is essential to ensure meiotic stability and optimal fertility of the species. However, the mechanisms preventing multivalent recombination in polyploids remain obscure. We studied the role of the synaptonemal complex in polyploid meiosis by mutating the transverse filament component ZYP1 in allotetraploid Brassica napus and autotetraploid Arabidopsis. In B. napus, a mutation of all four ZYP1 copies results in multivalent pairing accompanied by pairing partner switches, nonhomologous recombination, and interlocks, leading to severe chromosome entanglement and fertility abortion. The presence of only one functional allele of ZYP1 compromises synapsis and multivalent associations occur at nonsynaptic regions. Moreover, the disruption of ZYP1 causes a complete shift from predominantly multivalent pairing to exclusively multivalent pairing in pachytene cells of synthetic autotetraploid Arabidopsis thaliana, resulting in a dramatic increase in the frequency of multivalents at metaphase I. We conclude that the ZYP1-mediated assembly of the synaptonemal complex facilitates the pairwise homologous pairing and recombination in both allopolyploid and autopolyploid species and plays a key role in ensuring a diploid-like bivalent formation in polyploid meiosis.

Variation analysis and comparison of leaf and fruit traits of triploid hybrid progeny in jujube

Introduction

Polyploid hybrid progeny have both ploidy and hybridization effect, and abound in genetic variation of traits, which is an important material for the breeding of excellent new varieties.Ploidy breeding is an important means to improve and cultivate new varieties, which could overcome distant hybridization incompatibility and play a great significance to species evolution and environmental adaptation.Therefore, triploid breeding has a wide range of application value in germplasm innovation and cultivation of excellent new varieties of fruit trees.

Methods

In order to reveal the trait characteristics and variation analysis of leaves and fruits of triploid hybrids, the ploidy identifications and SSR analysis were carried out through all progeny, and the leaf, stomata, thorn, fruit quality and other traits were compared and analyzed between the triploid and diploid progeny. The genetic variation of the triploid progeny were further analyzed, which could provide reference for hybrid parents selection, offspring traits prediction, ploidy breeding of jujube.

Results

The results indicated that the triploid progeny exhibited significantly higher values for leaf width, straight thorn length, and stomatal length compared to diploid individuals. However, the leaf shape index and stomatal density were significantly lower in triploids than in diploids. Furthermore, a low genetic trend was observed for leaf traits in triploid progeny, while needle prick traits displayed a high genetic trend. In contrast, stomatal width and stomatal density showed moderate to low genetic trends. Significantly, the single fruit weight, single fruit kernel weight and soluble solids content were significantly higher in triploids compared to diploids. However, the kernel index and titratable acid content were significantly lower in triploids than diploids. The genetic trend showed a high inclination towards single fruit weight, fruit length, fruit shape index, kernel transverse diameter and vitamin C content in triploid offspring. The edible rate exhibited a moderate genetic trend, while kernel longitudinal diameter, kernel index, and titratable acid content displayed a low genetic trend.

Discussion

First, the occurrence of polypoloid hybrid progeny. Second, triploid hybrid progeny of jujube has typical polypolid traits. Finally, abondance of genetic variations of traits in triploid progeny.

Morpho-histological and Transcriptome Analysis Reveal the Unreduced Sperm Formation Mechanism in cdk1-Depletion Zebrafish

Cyclin-dependent kinases (Cdks) are major molecules related to cell cycle regulation. Polyploidy can be caused by the production of unreduced gametes, which is often related to the abnormal cell cycle of germ cells. Here, we successfully constructed a cdk1 mutation line (cdk1+/-) in zebrafish, a commonly used model organism. It showed that cdk1 depletion resulted in the generation of both polyploid and aneuploid embryos of WT♀ × cdk1+/-♂ zebrafish. In addition to normal sperms (1N), the depletion of cdk1 in zebrafish also led to the production of some large-head 2N sperms and higher ploidy sperms. Results of bivalent analysis of testis and ultrastructure analysis of spermatogonia suggested that the production of these large-head sperms was due to spermatogonia chromosome doubling in cdk1+/- zebrafish. Transcriptome analysis revealed aberrant expressions of some cell cycle and DNA replication-related genes in the early testis of cdk1+/- zebrafish relative to WT zebrafish. Through STRING correlation analysis, we further proved that cdk1 depletion affected the mitosis process and endoduplication initiation of spermatogonia by regulating expressions of some proteins related to cell cycle (i.e., Espl1 and Pp1) and DNA replication (i.e., Orc1 and Rnaseh2b), thereby leading to the formation of unreduced sperms. This study provides important information on revealing the molecular mechanisms of unreduced gamete formation caused by cdk1 mutation. Meanwhile, it also provides an important reference for the creation of fish polyploid germplasm.

An adventurous journey toward and away from fern apomixis: Insights from genome size and spore abortion patterns

PREMISE

Apomixis in ferns is relatively common and obligatory. Sterile hybrids may restore fertility via apomixis at a cost of long-term genetic stagnation. In this study, we outlined apomixis as a possible temporary phase leading to sexuality and analyzed factors relating to transitioning to and away from apomixis, such as unreduced and reduced spore formation in apomict and apo-sex hybrid ferns.

METHODS

We analyzed the genome size of 15 fern species or hybrids ("taxa") via flow cytometry. The number of reduced and unreduced gametophytes was established as a proxy for viable spore formation of either type. We also calculated the spore abortion ratio (sign of reduced spores) in several taxa, including the apo-sex hybrid Dryopteris × critica and its 16 apomictically formed offspring.

RESULTS

Four of 15 sampled taxa yielded offspring variable in genome size. Specifically, each variable taxon formed one viable reduced plant among 12-451 sampled gametophytes per taxon. Thus, haploid spore formation in the studied apomicts was very rare but possible. Spore abortion analyses indicated gradually decreasing abortion (haploid spore formation) over time. In Dryopteris × critica, abortion decreased from 93.8% to mean 89.5% in one generation.

CONCLUSIONS

Our results support apomixis as a transitionary phase toward sexuality. Newly formed apomicts hybridize with sexual relatives and continue to form haploid spores early on. Thus, they may get the genomic content necessary for regular meiosis and restore sexuality. If the missing relative goes extinct, the lineage gets locked into apomixis as may be the case with the Dryopteris affinis complex.

Exploring the patterns of evolution: Core thoughts and focus on the saltational model

The Modern Synthesis, a pillar in biological thought, united Darwin's species origin concepts with Mendel's laws of character heredity, providing a comprehensive understanding of evolution within species. Highlighting phenotypic variation and natural selection, it elucidated the environment's role as a selective force, shaping populations over time. This framework integrated additional mechanisms, including genetic drift, random mutations, and gene flow, predicting their cumulative effects on microevolution and the emergence of new species. Beyond the Modern Synthesis, the Extended Evolutionary Synthesis expands perspectives by recognizing the role of developmental plasticity, non-genetic inheritance, and epigenetics. We suggest that these aspects coexist in the plant evolutionary process; in this context, we focus on the saltational model, emphasizing how saltation events, such as dichotomous saltation, chromosomal mutations, epigenetic phenomena, and polyploidy, contribute to rapid evolutionary changes. The saltational model proposes that certain evolutionary changes, such as the rise of new species, may result suddenly from single macromutations rather than from gradual changes in DNA sequences and allele frequencies within a species over time. These events, observed in domesticated and wild higher plants, provide well-defined mechanistic bases, revealing their profound impact on plant diversity and rapid evolutionary events. Notably, next-generation sequencing exposes the likely crucial role of allopolyploidy and autopolyploidy (saltational events) in generating new plant species, each characterized by distinct chromosomal complements. In conclusion, through this review, we offer a thorough exploration of the ongoing dissertation on the saltational model, elucidating its implications for our understanding of plant evolutionary processes and paving the way for continued research in this intriguing field.

Incorrect recombination partner associations contribute to meiotic instability of neo-allopolyploid Arabidopsis suecica

Combining two or more related homoeologous genomes in a single nucleus, newly formed allopolyploids must rapidly adapt meiosis to restore balanced chromosome segregation, production of euploid gametes and fertility. The poor fertility of such neo-allopolyploids thus strongly selects for the limitation or avoidance of genetic crossover formation between homoeologous chromosomes. In this study, we have reproduced the interspecific hybridization between Arabidopsis thaliana and Arabidopsis arenosa leading to the allotetraploid Arabidopsis suecica and have characterized the first allopolyploid meioses. First-generation neo-allopolyploid siblings vary considerably in fertility, meiotic behavior and levels of homoeologous recombination. We show that centromere dynamics at early meiosis is altered in synthetic neo-allopolyploids compared with evolved A. suecica, with a significant increase in homoeologous centromere interactions at zygotene. At metaphase I, the presence of multivalents involving homoeologous chromosomes confirms that homoeologous recombination occurs in the first-generation synthetic allopolyploid plants and this is associated with a significant reduction in homologous recombination, compared to evolved A. suecica. Together, these data strongly suggest that the fidelity of recombination partner choice, likely during the DNA invasion step, is strongly impaired during the first meiosis of neo-allopolyploids and requires subsequent adaptation.

Polyploid speciation in Zea (Poaceae): cytogenetic insights

MAIN CONCLUSION

The analysis of meiotic pairing affinities and genomic formulae in species and hybrids of Zea allowed us to speculate an evolutionary model to recreate the ancient polyploidization of maize and allied species. The meiotic pairing affinities and the genomic formulae analysis in Zea species and hybrids obtained in new and previous crosses, together with the molecular data known in the genus, allowed us to speculate an evolutionary model to attempt to recreate the ancient polyploidization process of Zea species. We propose that x = 5 semispecies are the ancestors of all modern species of the genus. The complex evolutionary process that originated the different taxa could be included hybridization between sympatric diploid ancestral semispecies (2n = 10) and recurrent duplication of the hybrid chromosome number, resulting in distinct auto- and allopolyploids. After the merger and doubling of independent genomes would have undergone cytological and genetical diploidization, implying revolutionary changes in genome organization and genic balance processes. Based on the meiotic behaviour of the 2n = 30 hybrids, that showed homoeology between the A subgenomes of all parental species, we propose that this subgenome A would be pivotal in all the species and would have conserved the rDNA sequences and the pairing regulator locus (PrZ). In the hypothetical model postulated here, the ancestral semispecies with the pivotal subgenome A would have had a wide geographic distribution, co-occurring and hybridizing with the semispecies harbouring B subgenomes, thus enabling sympatric speciation.

Separating phases of allopolyploid evolution with resynthesized and natural Capsella bursa-pastoris

Allopolyploidization is a frequent evolutionary transition in plants that combines whole-genome duplication (WGD) and interspecific hybridization. The genome of an allopolyploid species results from initial interactions between parental genomes and long-term evolution. Distinguishing the contributions of these two phases is essential to understanding the evolutionary trajectory of allopolyploid species. Here, we compared phenotypic and transcriptomic changes in natural and resynthesized Capsella allotetraploids with their diploid parental species. We focused on phenotypic traits associated with the selfing syndrome and on transcription-level phenomena such as expression-level dominance (ELD), transgressive expression (TRE), and homoeolog expression bias (HEB). We found that selfing syndrome, high pollen, and seed quality in natural allotetraploids likely resulted from long-term evolution. Similarly, TRE and most down-regulated ELD were only found in natural allopolyploids. Natural allotetraploids also had more ELD toward the self-fertilizing parental species than resynthesized allotetraploids, mirroring the establishment of the selfing syndrome. However, short-term changes mattered, and 40% of the cases of ELD in natural allotetraploids were already observed in resynthesized allotetraploids. Resynthesized allotetraploids showed striking variation of HEB among chromosomes and individuals. Homoeologous synapsis was its primary source and may still be a source of genetic variation in natural allotetraploids. In conclusion, both short- and long-term mechanisms contributed to transcriptomic and phenotypic changes in natural allotetraploids. However, the initial gene expression changes were largely reshaped during long-term evolution leading to further morphological changes.

Genomic and Cytogenetic Analysis of Synthetic Polyploids between Diploid and Tetraploid Cotton (Gossypium) Species

Cotton (Gossypium spp.) is the most important natural fiber source in the world. The genetic potential of cotton can be successfully and efficiently exploited by identifying and solving the complex fundamental problems of systematics, evolution, and phylogeny, based on interspecific hybridization of cotton. This study describes the results of interspecific hybridization of G. herbaceum L. (A1-genome) and G. mustelinum Miers ex Watt (AD4-genome) species, obtaining fertile hybrids through synthetic polyploidization of otherwise sterile triploid forms with colchicine (C22H25NO6) treatment. The fertile F1C hybrids were produced from five different cross combinations: (1) G. herbaceum subsp. frutescens × G. mustelinum; (2) G. herbaceum subsp. pseudoarboreum × G. mustelinum; (3) G. herbaceum subsp. pseudoarboreum f. harga × G. mustelinum; (4) G. herbaceum subsp. africanum × G. mustelinum; (5) G. herbaceum subsp. euherbaceum (variety A-833) × G. mustelinum. Cytogenetic analysis discovered normal conjugation of bivalent chromosomes in addition to univalent, open, and closed ring-shaped quadrivalent chromosomes at the stage of metaphase I in the F1C and F2C hybrids. The setting of hybrid bolls obtained as a result of these crosses ranged from 13.8-92.2%, the fertility of seeds in hybrid bolls from 9.7-16.3%, and the pollen viability rates from 36.6-63.8%. Two transgressive plants with long fiber of 35.1-37.0 mm and one plant with extra-long fiber of 39.1-41.0 mm were identified in the F2C progeny of G. herbaceum subsp. frutescens × G. mustelinum cross. Phylogenetic analysis with 72 SSR markers that detect genomic changes showed that tetraploid hybrids derived from the G. herbaceum × G. mustelinum were closer to the species G. mustelinum. The G. herbaceum subsp. frutescens was closer to the cultivated form, and its subsp. africanum was closer to the wild form. New knowledge of the interspecific hybridization and synthetic polyploidization was developed for understanding the genetic mechanisms of the evolution of tetraploid cotton during speciation. The synthetic polyploids of cotton obtained in this study would provide beneficial genes for developing new cotton varieties of the G. hirsutum species, with high-quality cotton fiber and strong tolerance to biotic or abiotic stress. In particular, the introduction of these polyploids to conventional and molecular breeding can serve as a bridge of transferring valuable genes related to high-quality fiber and stress tolerance from different cotton species to the new cultivars.

Telomere and subtelomere high polymorphism might contribute to the specificity of homologous recognition and pairing during meiosis in barley in the context of breeding

Barley (Hordeum vulgare) is one of the most popular cereal crops globally. Although it is a diploid species, (2n = 2x = 14) the study of its genome organization is necessary in the framework of plant breeding since barley is often used in crosses with other cereals like wheat to provide them with advantageous characters. We already have an extensive knowledge on different stages of the meiosis, the cell division to generate the gametes in species with sexual reproduction, such as the formation of the synaptonemal complex, recombination, and chromosome segregation. But meiosis really starts with the identification of homologous chromosomes and pairing initiation, and it is still unclear how chromosomes exactly choose a partner to appropriately pair for additional recombination and segregation. In this work we present an exhaustive molecular analysis of both telomeres and subtelomeres of barley chromosome arms 2H-L, 3H-L and 5H-L. As expected, the analysis of multiple features, including transposable elements, repeats, GC content, predicted CpG islands, recombination hotspots, G4 quadruplexes, genes and targeted sequence motifs for key DNA-binding proteins, revealed a high degree of variability both in telomeres and subtelomeres. The molecular basis for the specificity of homologous recognition and pairing occurring in the early chromosomal interactions at the start of meiosis in barley may be provided by these polymorphisms. A more relevant role of telomeres and most distal part of subtelomeres is suggested.

Homoeologous evolution of the allotetraploid genome of Poa annua L

BACKGROUND

Poa annua (annual bluegrass) is an allotetraploid turfgrass, an agronomically significant weed, and one of the most widely dispersed plant species on earth. Here, we report the chromosome-scale genome assemblies of P. annua's diploid progenitors, P. infirma and P. supina, and use multi-omic analyses spanning all three species to better understand P. annua's evolutionary novelty.

RESULTS

We find that the diploids diverged from their common ancestor 5.5 - 6.3 million years ago and hybridized to form P. annua ≤ 50,000 years ago. The diploid genomes are similar in chromosome structure and most notably distinguished by the divergent evolutionary histories of their transposable elements, leading to a 1.7 × difference in genome size. In allotetraploid P. annua, we find biased movement of retrotransposons from the larger (A) subgenome to the smaller (B) subgenome. We show that P. annua's B subgenome is preferentially accumulating genes and that its genes are more highly expressed. Whole-genome resequencing of several additional P. annua accessions revealed large-scale chromosomal rearrangements characterized by extensive TE-downsizing and evidence to support the Genome Balance Hypothesis.

CONCLUSIONS

The divergent evolutions of the diploid progenitors played a central role in conferring onto P. annua its remarkable phenotypic plasticity. We find that plant genes (guided by selection and drift) and transposable elements (mostly guided by host immunity) each respond to polyploidy in unique ways and that P. annua uses whole-genome duplication to purge highly parasitized heterochromatic sequences. The findings and genomic resources presented here will enable the development of homoeolog-specific markers for accelerated weed science and turfgrass breeding.

Mitotic defects lead to unreduced sperm formation in cdk1-/- mutants

Unreduced gametes, that are important for species evolution and agricultural development, are generally believed to be formed by meiotic defects. However, we found that male diploid loach (Misgurnus anguillicaudatus) could produce not only haploid sperms, but also unreduced sperms, after cyclin-dependent kinase 1 gene (cdk1, one of the most important kinases in regulating cell mitosis) deletion. Observations on synaptonemal complexes of spermatocyte in prophase of meiosis and spermatogonia suggested that the number of chromosomes in some spermatogonia of cdk1^-/- loach doubled, leading to unreduced diploid sperm production. Then, transcriptome analysis revealed aberrant expressions of some cell cycle-related genes (such as ppp1c and gadd45) in spermatogonia of cdk1^-/- loach relative to wild-type loach. An in vitro and in vivo experiment further validated that Cdk1 deletion in diploid loach resulted in mitotic defects, leading to unreduced diploid sperm formation. In addition, we found that cdk1^-/- zebrafish could also produce unreduced diploid sperms. This study provides important information on revealing the molecular mechanisms behind unreduced gamete formation through mitotic defects, and lays the foundation for a novel strategy for fish polyploidy creation by using cdk1 mutants to produce unreduced sperms, which can then be used to obtain polyploidy, proposed to benefit aquaculture.

Patterns, mechanisms, and consequences of homoeologous exchange in allopolyploid angiosperms: a genomic and epigenomic perspective

Allopolyploids result from hybridization between different evolutionary lineages coupled with genome doubling. Homoeologous chromosomes (chromosomes with common shared ancestry) may undergo recombination immediately after allopolyploid formation and continue over successive generations. The outcome of this meiotic pairing behavior is dynamic and complex. Homoeologous exchanges (HEs) may lead to the formation of unbalanced gametes, reduced fertility, and selective disadvantage. By contrast, HEs could act as sources of novel evolutionary substrates, shifting the relative dosage of parental gene copies, generating novel phenotypic diversity, and helping the establishment of neo-allopolyploids. However, HE patterns vary among lineages, across generations, and even within individual genomes and chromosomes. The causes and consequences of this variation are not fully understood, though interest in this evolutionary phenomenon has increased in the last decade. Recent technological advances show promise in uncovering the mechanistic basis of HEs. Here, we describe recent observations of the common patterns among allopolyploid angiosperm lineages, underlying genomic and epigenomic features, and consequences of HEs. We identify critical research gaps and discuss future directions with far-reaching implications in understanding allopolyploid evolution and applying them to the development of important phenotypic traits of polyploid crops.

10th Anniversary of Plants-Recent Advances and Further Perspectives

Published for the first time in 2012, Plants will celebrate its 10th anniversary [...].

Salmonidae Genome: Features, Evolutionary and Phylogenetic Characteristics

The salmon family is one of the most iconic and economically important fish families, primarily possessing meat of excellent taste as well as irreplaceable nutritional and biological value. One of the most common and, therefore, highly significant members of this family, the Atlantic salmon (Salmo salar L.), was not without reason one of the first fish species for which a high-quality reference genome assembly was produced and published. Genomic advancements are becoming increasingly essential in both the genetic enhancement of farmed salmon and the conservation of wild salmon stocks. The salmon genome has also played a significant role in influencing our comprehension of the evolutionary and functional ramifications of the ancestral whole-genome duplication event shared by all Salmonidae species. Here we provide an overview of the current state of research on the genomics and phylogeny of the various most studied subfamilies, genera, and individual salmonid species, focusing on those studies that aim to advance our understanding of salmonid ecology, physiology, and evolution, particularly for the purpose of improving aquaculture production. This review should make potential researchers pay attention to the current state of research on the salmonid genome, which should potentially attract interest in this important problem, and hence the application of new technologies (such as genome editing) in uncovering the genetic and evolutionary features of salmoniforms that underlie functional variation in traits of commercial and scientific importance.

Frequent spontaneous structural rearrangements promote rapid genome diversification in a Brassica napus F1 generation

In a cross between two homozygous Brassica napus plants of synthetic and natural origin, we demonstrate that novel structural genome variants from the synthetic parent cause immediate genome diversification among F1 offspring. Long read sequencing in twelve F1 sister plants revealed five large-scale structural rearrangements where both parents carried different homozygous alleles but the heterozygous F1 genomes were not identical heterozygotes as expected. Such spontaneous rearrangements were part of homoeologous exchanges or segmental deletions and were identified in different, individual F1 plants. The variants caused deletions, gene copy-number variations, diverging methylation patterns and other structural changes in large numbers of genes and may have been causal for unexpected phenotypic variation between individual F1 sister plants, for example strong divergence of plant height and leaf area. This example supports the hypothesis that spontaneous de novo structural rearrangements after de novo polyploidization can rapidly overcome intense allopolyploidization bottlenecks to re-expand crops genetic diversity for ecogeographical expansion and human selection. The findings imply that natural genome restructuring in allopolyploid plants from interspecific hybridization, a common approach in plant breeding, can have a considerably more drastic impact on genetic diversity in agricultural ecosystems than extremely precise, biotechnological genome modifications.

Interspecies Recombination-Led Speciation of a Novel Geminivirus in Pakistan

Recombination between isolates of different virus species has been known to be one of the sources of speciation. Weeds serve as mixing vessels for begomoviruses, infecting a wide range of economically important plants, thereby facilitating recombination. Chenopodium album is an economically important weed spread worldwide. Here, we present the molecular characterization of a novel recombinant begomovirus identified from C. album in Lahore, Pakistan. The complete DNA- A genome of the virus associated with the leaf distortion occurred in the infected C. album plants was cloned and sequenced. DNA sequence analysis showed that the nucleotide sequence of the virus shared 93% identity with those of the rose leaf curl virus and the duranta leaf curl virus. Interestingly, this newly identified virus is composed of open reading frames (ORFs) from different origins. Phylogenetic networks and complementary recombination detection methods revealed extensive recombination among the sequences. The infectious clone of the newly detected virus was found to be fully infectious in C. album and Nicotiana benthamiana as the viral DNA was successfully reconstituted from systemically infected tissues of inoculated plants, thus fulfilling Koch's postulates. Our study reveals a new speciation of an emergent ssDNA plant virus associated with C. album through recombination and therefore, proposed the tentative name 'Chenopodium leaf distortion virus' (CLDV).

Advances and Perspectives for Polyploidy Breeding in Orchids

The orchid market is a dynamic horticultural business in which novelty and beauty command high prices. The two main interests are the development of flowers, from the miniature to the large and showy, and their fragrance. Overall organ size might be modified by doubling the chromosome number, which can be accomplished by careful study of meiotic chromosome disjunction in hybrids or species. Meiosis is the process in which diploid (2n) pollen mother cells recombine their DNA sequences and then undergo two rounds of division to give rise to four haploid (n) cells. Thus, by interfering in chromosome segregation, one can induce the development of diploid recombinant cells, called unreduced gametes. These unreduced gametes may be used for breeding polyploid progenies with enhanced fertility and large flower size. This review provides an overview of developments in orchid polyploidy breeding placed in the large context of meiotic chromosome segregation in the model plants Arabidopsis thaliana and Brassica napus to facilitate molecular translational research and horticultural innovation.

Impact of polyploidy on plant tolerance to abiotic and biotic stresses

Polyploidy, defined as the coexistence of three or more complete sets of chromosomes in an organism's cells, is considered as a pivotal moving force in the evolutionary history of vascular plants and has played a major role in the domestication of several crops. In the last decades, improved cultivars of economically important species have been developed artificially by inducing autopolyploidy with chemical agents. Studies on diverse species have shown that the anatomical and physiological changes generated by either natural or artificial polyploidization can increase tolerance to abiotic and biotic stresses as well as disease resistance, which may positively impact on plant growth and net production. The aim of this work is to review the current literature regarding the link between plant ploidy level and tolerance to abiotic and biotic stressors, with an emphasis on the physiological and molecular mechanisms responsible for these effects, as well as their impact on the growth and development of both natural and artificially generated polyploids, during exposure to adverse environmental conditions. We focused on the analysis of those types of stressors in which more progress has been made in the knowledge of the putative morpho-physiological and/or molecular mechanisms involved, revealing both the factors in common, as well as those that need to be addressed in future research.