Global Downward Attunement of Two Parental Transcriptomes in Allopolyploid xBrassicoraphanus

Expressional alteration of duplicated genes after polyploidization is a largely unknown process. To investigate the polyploidization effect, we performed NGS-associated transcriptome analyses of a synthetic intergeneric hybrid xBrassicoraphanus cv. BB1 and its two representative parents, Brassica rapa accession Chiifu-401-42 and Raphanus sativus accession WG10039. Through de novo assemblies and homology analyses, we obtained 8,367 homologous unigene sets from these three species. Most of unigenes which showed altered expressions were down-regulated in BB1, and 87% of paralogs in BB1 was attuned their expression to the similar level. Considering the mid-parent phenotypes in the hybrid progeny, the global downward attunements of transcriptome might be a causal step to stabilize the coexistence of two distinct genomes in a single organism. These approaches give us more detailed insight into the expressional alteration of each paralogs in BB1, compare to the hybridization based mid-parent value approaches.