Asymmetrical effects of autopolyploidization on organ size and gene expression in Brassica rapa and B. oleracea

Abstract

Autopolyploidization usually accompanied with the enlargement of single organs or even the whole plant. The potential mechanism is still unclear. Here, we investigated the genome heterozygosity and compared the effect of polyploidization on organ size and global gene expression of two Brassica diploids, B. rapa and B. oleracea. Both vegetative and reproductive organs of enlarged size were observed for the aotutetraploid of B. rapa. In sharp contrast, the B. oleracea aotutetraploid did not show increased organ size except for the seeds. Transcriptome analysis in young silique wall revealed significant more differentially expressed genes (DEGs) between autotetraploid and diploid in B. rapa than those in B. oleracea. These DEGs were distributed randomly on chromosomes and did not show association with those heterozygosity regions. Several genes involved in cell wall biosynthesis were significantly up-regulated in aotutetraploid B. rapa which was well consist with the enlarged siliques. Interestingly, two significantly down-regulated FLOWERING LOCUS T (FT) genes were found in silique wall of autotetraploid B. oleracea. These findings indicated autopolyploidization consequence on organ size and gene expression in Brassica was species-specific and organ-specific which might be under genetic control related to the genome structure and composition.