Scientists from the John Innes Centre have identified a gene that has deep-rooted effects on seed production in wheat. Through gene-editing techniques, they identified and explained the main gene, ZIP4, that maintains 50% of yield in this worldwide crop.
Gene-editing techniques helped to identify and explain the key gene, ZIP4, in wheat. Image Credit: John Innes Centre.
The breakthrough represents a stimulating, new possibility to breed high-yield, elite wheat varieties through an innovative mutation of the gene, while enabling the introduction of vitally significant traits like disease resistance and heat resilience.
As part of the study, Professor Graham Moore’s research team leveraged recent advancements in wheat research technology to elucidate genetic elements that have perplexed researchers for over six decades. The study was published in Scientific Reports.
Our study describes the identification of a gene, ZIP4 and its phenotype, responsible for the preservation of 50% grain in wheat. We can now aim to identify variants of the gene with effects that give wheat yield resilience to climate change.”
Graham Moore, Professor, John Innes Centre
The development of climate change-resilient wheat will help secure a crop on which 2.5 billion people rely. Several plant species including a majority of the flowering plants are polyploid, that is, they exhibit multiple genomes. The polyploid wheat genome emerged as a combination of wild grasses that cross-fertilized, almost 10,000 years ago, in the Middle East.
As part of the process called polyploidization, fertility is preserved through mechanisms that have evolved to regulate the behavior of these multiple genomes at the time of meiosis, the sexual reproduction phase within cells. When wheat polyploidization occurs, the key meiotic gene ZIP4 duplicates from chromosome 3 into chromosome 5B.
Earlier studies had demonstrated that the duplicated gene has two major functions in stabilizing the wheat genome at the time of meiosis: promotion of reliable chromosome pairing and inhibition of crossover between associated chromosomes. For over six decades, the inhibition function was thought to be behind grain yield and genome stability and thus informed breeding decisions.
Scientists in the Moore group employed CRISPR-Cas9 genome editing methods to develop a mutant plant where the ZIP4 5B gene was deleted, resulting in the loss of both its functions. This mutation led to 50% fewer grains, verifying the crucial role of ZIP4 5B in wheat fertility.
Then, the researchers developed an innovative “separation of function” ZIP4 5B mutant plant that had lost the crossover suppression phenotype but had still retained the potential to boost accurate pairing.
Fascinatingly, the “promotion of correct pairing” phenotype in the separation of function ZIP4 5B mutant wheat retained chromosome stability and preserved the grain number. The findings revealed that astonishingly, despite the loss of crossover inhibition phenotype, wheat fertility did not drop even when the other function was preserved.
Until now the importance of this second phenotype to the preservation of grain number has been unclear. Our study has shown that the new mutant should now be used in wheat breeding to maintain yield and, because it does not have the suppression function, to increase the chance of successful introgression of desirable wild relative chromosome segments into wheat.”
Graham Moore, Professor, John Innes Centre
Meiosis is a function influenced by higher temperatures. The focus of the research is to find the variations of the ZIP4 gene that maintain meiotic stability and fertility under various temperature regimes.
Duplication of the ZIP4 gene from chromosome 3 into chromosome 5B after polyploidisation is likely to have had an extraordinary impact on agriculture and human nutrition. The separation of function mutants described in this study will lead to more successful introgressions in breeding.”
Dr Azahara Martin, Study First Author, John Innes Centre
Martín, A. C., et al. (2021) A separation-of-function ZIP4 wheat mutant allows crossover between related chromosomes and is meiotically stable. Scientific Reports. doi.org/10.1038/s41598-021-01379-z.