Can We Use Gene-Editing to Induce Apomixis in Sexual Plants?

Scheben, Armin; Hojsgaard, Diego

doi:10.3390/genes11070781

Cited by 19 publications

(11 citation statements)

References 196 publications

(269 reference statements)

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“…The above considerations that influence the response of grasses concerning tissue culture, plant regeneration, and plant transformation methods are also important for GE. The knowledge generated from functional studies in apomictic grasses through transgenesis could support the induction of apomixis via GE in sexual plants to preserve the hybrid vigor for multiple generations in economically important crops (Scheben and Hojsgaard, 2020;Fiaz et al, 2021). However, the genomic information in apomictic grasses needed to perform GE is scarce and often unavailable.…”

Section: Significant Breakthroughs In Grass Transformation Alternative Dna-delivery Methodsmentioning

confidence: 99%

Genetic Transformation of Apomictic Grasses: Progress and Constraints

et al. 2021

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The available methods for plant transformation and expansion beyond its limits remain especially critical for crop improvement. For grass species, this is even more critical, mainly due to drawbacks in in vitro regeneration. Despite the existence of many protocols in grasses to achieve genetic transformation through Agrobacterium or biolistic gene delivery, their efficiencies are genotype-dependent and still very low due to the recalcitrance of these species to in vitro regeneration. Many plant transformation facilities for cereals and other important crops may be found around the world in universities and enterprises, but this is not the case for apomictic species, many of which are C4 grasses. Moreover, apomixis (asexual reproduction by seeds) represents an additional constraint for breeding. However, the transformation of an apomictic clone is an attractive strategy, as the transgene is immediately fixed in a highly adapted genetic background, capable of large-scale clonal propagation. With the exception of some species like Brachiaria brizantha which is planted in approximately 100 M ha in Brazil, apomixis is almost non-present in economically important crops. However, as it is sometimes present in their wild relatives, the main goal is to transfer this trait to crops to fix heterosis. Until now this has been a difficult task, mainly because many aspects of apomixis are unknown. Over the last few years, many candidate genes have been identified and attempts have been made to characterize them functionally in Arabidopsis and rice. However, functional analysis in true apomictic species lags far behind, mainly due to the complexity of its genomes, of the trait itself, and the lack of efficient genetic transformation protocols. In this study, we review the current status of the in vitro culture and genetic transformation methods focusing on apomictic grasses, and the prospects for the application of new tools assayed in other related species, with two aims: to pave the way for discovering the molecular pathways involved in apomixis and to develop new capacities for breeding purposes because many of these grasses are important forage or biofuel resources.

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Section: Significant Breakthroughs In Grass Transformation Alternative Dna-delivery Methodsmentioning

confidence: 99%

Genetic Transformation of Apomictic Grasses: Progress and Constraints

et al. 2021

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“…However, the variable penetrance of the trait between transgenic lines and siblings of the same line, the complexity of embryo development observed in rice lines with shifts to vivipary and absence of endosperm development [130] plus the lack of a reference genome of the apomictic species highly restrict the options to deeply characterize the PsASGR-BBML gene and the network of genes and/or protein interactions which may further promote parthenogenesis. This limits the chances of manipulating plants with enhanced transcriptional levels (see [20] in this issue).…”

Section: Molecular Control Of Apomixis In Apomictic Plantsmentioning

confidence: 99%

“…Examples are the feeble penetrance attained by synthetic apomixis-like mutants (see for example [162]), which expose the fact that changing radically key developmental steps likely require the coordination of multiple metabolic pathways, molecular signals, and cellular players. Unless a proper understanding of the genetic architecture of apomixis exists, the prospect for a genetic engineered apomictic crop remains equivocal (but see [20] other reviews in this issue).…”

Section: Overall Features Hypotheses In Conflict and The Quest For mentioning

confidence: 99%

“…Even if simultaneously modifying several key genes produces plants mimicking apomixis phenotypes, relevant knowledge about their genetic background and possible molecular interactions and responses to regulatory signals in developmental cascades during gametogenesis and embryo and endosperm developments will still be missing. This is likely the reason why characterized apomixis-like mutants often display low penetrance and paltry quality phenotypes (see discussion below and in [20]). In the case of apomixis technology, the central problem behind constraints to apomixis breeding is that the genomic background and molecular mechanisms that initiate apomixis and guide the formation of a functional clonal seed are still poorly understood.…”

Section: Introductionmentioning

confidence: 99%

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Apomixis Technology: Separating the Wheat from the Chaff

Hojsgaard

2020

Genes

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Projections indicate that current plant breeding approaches will be unable to incorporate the global crop yields needed to deliver global food security. Apomixis is a disruptive innovation by which a plant produces clonal seeds capturing heterosis and gene combinations of elite phenotypes. Introducing apomixis into hybrid cultivars is a game-changing development in the current plant breeding paradigm that will accelerate the generation of high-yield cultivars. However, apomixis is a developmentally complex and genetically multifaceted trait. The central problem behind current constraints to apomixis breeding is that the genomic configuration and molecular mechanism that initiate apomixis and guide the formation of a clonal seed are still unknown. Today, not a single explanation about the origin of apomixis offer full empirical coverage, and synthesizing apomixis by manipulating individual genes has failed or produced little success. Overall evidence suggests apomixis arise from a still unknown single event molecular mechanism with multigenic effects. Disentangling the genomic basis and complex genetics behind the emergence of apomixis in plants will require the use of novel experimental approaches benefiting from Next Generation Sequencing technologies and targeting not only reproductive genes, but also the epigenetic and genomic configurations associated with reproductive phenotypes in homoploid sexual and apomictic carriers. A comprehensive picture of most regulatory changes guiding apomixis emergence will be central for successfully installing apomixis into the target species by exploiting genetic modification techniques.

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“…Finally, an opinion piece summarizes the relevant molecular data and the three currently accepted but divergent hypotheses explaining the nature of apomixis to point to a probable single molecular event with a multigenic effect on reproductive development implicated in the origin of apomixis, remarking on the need to find a unifying molecular model to fully exploit apomixis technology [ 11 ]. In addition, Scheben and Hojsgaard [ 12 ] discuss alternative methods from the gene-editing toolbox and their feasible use to induce apomixis in sexual plants depending on the type of molecular model of the genetic control of apomixis that is chosen, and stress the importance of understanding the molecular basis of apomixis and its natural variation in apomictic plants for trait breeding and optimization in sexual ones.…”

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confidence: 99%