Crop traits for disease resistance, yield and climate resilience may become easier for breeders to access after researchers identified three genes that suppress recombination in chromosome regions where useful genetic variation has often remained out of reach.
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Disabling three genetic gatekeepers allowed recombination in normally inaccessible chromosome regions, potentially widening access to traits for disease resistance, yield and climate resilience.
Scientists have identified three genes that prevent genetic recombination across large sections of plant chromosomes, raising the prospect of making previously inaccessible crop traits available to breeders.
Researchers at the Max Planck Institute for Plant Breeding Research in Cologne found that disabling CTF18, SGO2 or SPF2 allowed DNA exchanges to occur near chromosome centromeres, where recombination is normally rare or absent.
The findings, published in Nature Plants, could eventually help breeders work with valuable genes that have remained locked together with undesirable genetic material, according to a press release.
Chromosome ‘Cold Zones’ Restrict Crop Improvement
When plants reproduce sexually, paired chromosomes exchange sections of DNA through crossover recombination. Breeders rely on this natural reshuffling to combine useful characteristics from different varieties or separate desirable genes from unwanted neighbouring traits.
Recombination, however, is not evenly distributed along chromosomes. Large regions surrounding the centromere—the structure involved in separating chromosomes during cell division—are effectively closed to crossovers.
These regions are known as recombination cold zones. In wheat and barley, they can cover more than half of each chromosome, severely limiting the genetic combinations available to breeders.
Around 18% of barley genes are located within these inaccessible regions. In tomato, a gene providing resistance to a damaging virus is trapped alongside millions of base pairs of unwanted DNA that breeders have been unable to remove for decades.
Three Genes Act as Recombination Gatekeepers
The team, led by Raphael Mercier, investigated the mechanisms that prevent crossovers near centromeres in the model plant Arabidopsis thaliana.
The researchers identified CTF18, SGO2 and SPF2 as genetic gatekeepers that independently suppress recombination in these regions.
When any one of the genes was disabled, crossovers appeared in chromosome areas where they had not previously been detected. Disabling SPF2 alone produced more than a threefold increase in recombination within the former cold zones.
Combining mutations produced an even stronger effect. This indicates that several separate molecular mechanisms work together to keep centromere-adjacent chromosome regions closed to genetic exchange.
Modified Plants Remain Healthy and Fertile
Most plants carrying the mutations grew normally, remained fertile and produced standard numbers of seeds. No growth defects were detected in any of the mutant plants.
Only the most extreme combinations of mutations reduced fertility. The results suggest that recombination can be increased substantially without seriously disrupting plant development or reproduction, at least under the conditions tested.
Further research will be required to establish whether the same approach is safe and effective in crop species.
Single Altered Copy May Be Enough
One of the most promising findings was that plants carrying only one disrupted copy of SPF2 or SGO2 already showed increased recombination in normally suppressed regions.
This co-dominant effect could make the mutations easier to use in breeding programmes because both copies of the gene would not need to be altered.
Breeders might therefore be able to introduce one of the mutations temporarily, produce a desired genetic combination and then remove the mutation through subsequent crossing.
The resulting crop variety would retain the newly combined traits without carrying the recombination-enhancing mutation itself.
Major Crops Could Be Next
The three genes are conserved across the plant kingdom and are also present in more distantly related organisms, including animals.
The researchers believe the findings could be translated to major crops such as wheat, barley, maize and tomato, where recombination cold zones are considerably larger than in Arabidopsis.
If the approach works in those crops, it could give breeders access to genes that have long remained beyond the reach of conventional crossing. This may make it easier to introduce disease resistance, remove undesirable linked traits and assemble combinations supporting higher yields or greater climate resilience.
The findings mark an early but potentially important step towards expanding the usable genetic diversity available to crop-breeding programmes.
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