LAUSR

Interspecific hybridization drives the evolution of angiosperms and can be used to introduce novel alleles for important traits or activate heterosis in crop breeding. Hybridization brings together gene expression networks from two different species, potentially causing global alterations of gene expression in the F1 plants which is called 'transcriptome shock'. Here, we explored such transcriptome shock in allotriploid Brassica hybrids. We generated interspecific F1 allotriploid hybrids between the allotetraploid species Brassica napus and three accessions of the diploid species Brassica rapa. RNA-seq of the F1 hybrids and the parental plants revealed that 26.34-30.89% of genes were differentially expressed between the parents. We also analyzed expression-level dominance (ELD) and homoeologue expression bias (HEB) between the parents and the F1 hybrids. The ELD biases of the Ar, An, and Cn subgenomes was genotype and stage dependent, whereas significant homoeologue expression bias was observed among three subgenomes from different parents. Furthermore, more genes were involved in trans regulation than cis regulation in allotriploid F1 hybrids. Our findings thus provide insight into the transcriptomic responses of cross-species hybrids and hybrids showing heterosis, as well as a new method for promoting the breeding of desirable traits in polyploid Brassica species.