In a recent advance, the Molecular Breeding and Innovation Team at the Vegetable and Flower Research Institute of the Chinese Academy of Agricultural Sciences successfully synthesized a hybrid tetraploid in the Brassicaceae family, unraveling the mechanisms underlying subgenome dominance in polyploids. The story, entitled “The lack of negative association between TE load and subgenome dominance in synthesized  Brassica allotetraploids”, was published in the Proceedings of the National Academy of Sciences ( PNAS ).

Polyploidization is important to the evolution of plants. Subgenome dominance is a distinct phenomenon associated with most allopolyploidization events. The evidence suggests that the differences in transposon density and methylation levels are negatively associated with the subgenome dominance. Thus, many researchers have suggested, ourselves included, that methylated transposons near genes serve to initiate subgenome dominance in the wide hybrid.

The study involved the distant hybridization of Chinese cabbage and cabbage to create a heterologous tetraploid. Through comprehensive transcriptome and methylation sequencing analyses of the parents and tetraploid progenies, the research team discovers that transposon density and methylation differences are not decisive factors in the establishment of subgenome dominance in polyploids. This challenges the previously held understanding of the relationship between transposons and subgenome dominance. Based on these findings, the researchers proposed a new perspective, suggesting that novel polyploids preserve distinct transcriptional regulatory efficiencies through the ‘nuclear chimera’ of subgenomes, consequently forming subgenome dominance.

This achievement holds significant implications for gaining a deeper understanding of the evolution of crop genome polyploidization and the creation of novel polyploid germplasm for crop breeding.

More information can be found through the link: https://doi.org/10.1073/pnas.2305208120

By Kang Zhang (zhangkang01@caas.cn)