A Reappraisal of the Evolutionary and Developmental Pathway of Apomixis and Its Genetic Control in Angiosperms

Barcaccia, Gianni; Palumbo, Fabio; Sgorbati, Sergio; Albertini, Emidio; Pupilli, Fulvio

doi:10.3390/genes11080859

Cited by 16 publications

(14 citation statements)

References 120 publications

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“…Firstly, facts about perennial TFGs must be pointed out, as most are polyploids and reproduce apomictically. Apomixis is asexual reproduction by seed (Barcaccia et al, 2020) producing genetically identical progeny (Hand and Koltunow, 2014). In both important genera of TFG, Megathyrsus and Urochloa, gametophytic apomixis subtype apospory occurs (Ozias-Akins and van Dijk, 2007) which is a mode of reproduction in which the embryo originates from a polyploid nucellar cell as a maternal clone by the seed (Valle and Savidan, 1996).…”

Section: Peculiarities In Breeding Perennial Tfgs: Polyploidy and Apomixismentioning

confidence: 99%

Genomic Selection in Tropical Forage Grasses: Current Status and Future Applications

et al. 2021

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The world population is expected to be larger and wealthier over the next few decades and will require more animal products, such as milk and beef. Tropical regions have great potential to meet this growing global demand, where pasturelands play a major role in supporting increased animal production. Better forage is required in consonance with improved sustainability as the planted area should not increase and larger areas cultivated with one or a few forage species should be avoided. Although, conventional tropical forage breeding has successfully released well-adapted and high-yielding cultivars over the last few decades, genetic gains from these programs have been low in view of the growing food demand worldwide. To guarantee their future impact on livestock production, breeding programs should leverage genotyping, phenotyping, and envirotyping strategies to increase genetic gains. Genomic selection (GS) and genome-wide association studies play a primary role in this process, with the advantage of increasing genetic gain due to greater selection accuracy, reduced cycle time, and increased number of individuals that can be evaluated. This strategy provides solutions to bottlenecks faced by conventional breeding methods, including long breeding cycles and difficulties to evaluate complex traits. Initial results from implementing GS in tropical forage grasses (TFGs) are promising with notable improvements over phenotypic selection alone. However, the practical impact of GS in TFG breeding programs remains unclear. The development of appropriately sized training populations is essential for the evaluation and validation of selection markers based on estimated breeding values. Large panels of single-nucleotide polymorphism markers in different tropical forage species are required for multiple application targets at a reduced cost. In this context, this review highlights the current challenges, achievements, availability, and development of genomic resources and statistical methods for the implementation of GS in TFGs. Additionally, the prediction accuracies from recent experiments and the potential to harness diversity from genebanks are discussed. Although, GS in TFGs is still incipient, the advances in genomic tools and statistical models will speed up its implementation in the foreseeable future. All TFG breeding programs should be prepared for these changes.

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Section: Peculiarities In Breeding Perennial Tfgs: Polyploidy and Apomixismentioning

confidence: 99%

Genomic Selection in Tropical Forage Grasses: Current Status and Future Applications

et al. 2021

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“…Diploid meiotic mutants producing viable and unreduced ( n ≥ 2) gametes have been discovered in numerous plants [ 58 ], and although complete penetrance is extremely uncommon, it is thought to be an almost ubiquitous behavior across the entire plant kingdom [ 59 ]. Practically speaking, unreduced gametes are largely employed for polyploidization processes, and to boost the heterosis effect in several crops, including alfalfa [ 51 , 60 ].…”

Section: Candidate Genes For Unreduced Gamete Production and Exploitation Of Genomic Resources For The Analysis Of Alfalfa Meiotic Mutantmentioning

confidence: 99%

A Review of Unreduced Gametes and Neopolyploids in Alfalfa: How to Fill the Gap between Well-Established Meiotic Mutants and Next-Generation Genomic Resources

Palumbo

Pasquali

Albertini

et al. 2021

Plants

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The gene flow mediated by unreduced gametes between diploid and tetraploid plants of the Medicago sativa–coerulea–falcata complex is pivotal for alfalfa breeding. Sexually tetraploidized hybrids could represent the best way to exploit progressive heterosis simultaneously derived from gene diversity, heterozygosity, and polyploidy. Moreover, unreduced gametes combined with parthenogenesis (i.e., apomixis) would enable the cloning of plants through seeds, providing a unique opportunity for the selection of superior genotypes with permanently fixed heterosis. This reproductive strategy has never been detected in the genus Medicago, but features of apomixis, such as restitutional apomeiosis and haploid parthenogenesis, have been reported. By means of an original case study, we demonstrated that sexually tetraploidized plants maintain apomeiosis, but this trait is developmentally independent from parthenogenesis. Alfalfa meiotic mutants producing unreduced egg cells revealed a null or very low capacity for parthenogenesis. The overall achievements reached so far are reviewed and discussed along with the efforts and strategies made for exploiting reproductive mutants that express apomictic elements in alfalfa breeding programs. Although several studies have investigated the cytological mechanisms responsible for 2n gamete formation and the inheritance of this trait, only a very small number of molecular markers and candidate genes putatively linked to unreduced gamete formation have been identified. Furthermore, this scenario has remained almost unchanged over the last two decades. Here, we propose a reverse genetics approach, by exploiting the genomic and transcriptomic resources available in alfalfa. Through a comparison with 9 proteins belonging to Arabidopsis thaliana known for their involvement in 2n gamete production, we identified 47 orthologous genes and evaluated their expression in several tissues, paving the way for novel candidate gene characterization studies. An overall view on strategies suitable to fill the gap between well-established meiotic mutants and next-generation genomic resources is presented and discussed.

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“…Therefore, functional shifts in components of sexual reproduction can be linked to genomic regions behaving as supergenes (in which even individual genes can be identified) rather than to complete haplomes. [78,[104][105][106][107][108][109] The above-stated conditions and the developmental and molecular…”

Section: Plants Fine-tune Asexuality Through Polyploidy and Supergenesmentioning

confidence: 99%

Skipping sex: A nonrecombinant genomic assemblage of complementary reproductive modules

Hojsgaard

Schartl

2020

BioEssays

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The unusual occurrence and developmental diversity of asexual eukaryotes remain a puzzle. De novo formation of a functioning asexual genome requires a unique assembly of sets of genes or gene states to disrupt cellular mechanisms of meiosis and gametogenesis, and to affect discrete components of sexuality and produce clonal or hemiclonal offspring. We highlight two usually overlooked but essential conditions to understand the molecular nature of clonal organisms, that is, a nonrecombinant genomic assemblage retaining modifiers of the sexual program, and a complementation between altered reproductive components. These subtle conditions are the basis for physiologically viable and genetically balanced transitions between generations. Genomic and developmental evidence from asexual animals and plants indicates the lack of complementation of molecular changes in the sexual reproductive program is likely the main cause of asexuals' rarity, and can provide an explanatory frame for the developmental diversity and lability of developmental patterns in some asexuals as well as for the discordant time to extinction estimations.

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A Reappraisal of the Evolutionary and Developmental Pathway of Apomixis and Its Genetic Control in Angiosperms

Cited by 16 publications

References 120 publications

Genomic Selection in Tropical Forage Grasses: Current Status and Future Applications

Genomic Selection in Tropical Forage Grasses: Current Status and Future Applications

A Review of Unreduced Gametes and Neopolyploids in Alfalfa: How to Fill the Gap between Well-Established Meiotic Mutants and Next-Generation Genomic Resources

Skipping sex: A nonrecombinant genomic assemblage of complementary reproductive modules

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