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Presenter

Nikolai Adamski, Department of Crop Genetics, John Innes Centre, UK

Outline

The tetraploid wheat Triticum polonicum is characterized by long glumes and grains. More than 100 years ago, it was shown that these traits were determined by a single locus, which was later designated as P1. We have cloned the gene underlying the P1 locus using two bi-parental mapping populations. We mapped the A-genome homolog of “VEGETATIVE TO REPRODUCTIVE TRANSITION 2” (VRT-A2) as the only candidate gene for the P1 locus. We termed the wildtype allele as VRT-A2a and the allele from T. polonicum as VRT-A2b. All accessions of T. polonicum carried the exact same allele of VRT-A2, suggesting a single common origin.

We transformed the hexaploid cultivar ‘Fielder’ with the VRT-A2b allele under control of its native promoter. Both in the T and T1 generation, the transformed plants showed an elongation of their glumes and grains, thus validating VRT-A2 as the causal gene underlying the P1 locus. We showed that VRT-A2b was ectopically expressed in developing wheat spikes, glumes, and grains compared to the wildtype allele. We further showed, using the transgenic plants, that the glume and grain phenotypes correlated with VRT-A2 transcription levels, suggesting a causal correlation.

We identified two motifs in the first intron of VRT-A2 that are conserved across grasses, including rice, maize, and sorghum. We hypothesize that these motifs are required to switch off VRT-A2 expression. By studying these motifs, we aim to identify potential binding partners and decipher the regulatory network controlling VRT2 expression.

References

• Adamski et al., 2021 ( https://doi.org/10.1093/plcell/koab119 )
• Liu et al., 2021 ( https://doi.org/10.1016/j.molp.2021.05.021 )

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