Comparative transcriptome analysis reveals the biological processes of hybridization incompatibility between Brassica napus and B. oleracea

Abstract

It is an important breeding strategy to improve Brassica napus by crossing with its parental species, B. oleracea and B. rapa. Interspecific hybridization between B. napus and B. rapa is compatible with high rate of survival embryo, while the hybridization between B. napus and B. oleracea is incompatible with high occurrence of embryo abortion. To understand the diverse embryo fate in the two interspecific hybridizations, here the siliques of B. napus pollinated with B. oleracea (AE) and B. rapa (NE) were employed for transcriptome sequencing at 8 and 16 days after pollination. Compared with NE and female, there were 1274 and 1698 differentially expressed genes (DEGs) in AE at 8 and 16 days after pollination (AE8 and AE16), which were significantly enriched into 67 and 72 GO terms, respectively. Of which 9 and 15 GO terms in cell growth, cell wall formation harbored high ratio of down-regulated expression DEGs (96/131 in AE8, 174/235 in AE16), while 12 and 17 GO terms in the processes of photosynthesis, photorespiration, peroxisome, oxidative stress and systemic acquired resistance harbored high ratio of up-regulated expression DEGs (222/304 in AE8, 214/287 in AE16). A high level of O2−, H2O2 content and antioxidation activity (SOD, CAT) was tested in the siliques of B. napus pollinated with B. oleracea. Our data suggest that disorder of plant hormone metabolism, retardation of cell morphogenesis and the accumulation of reactive oxygen species (ROS) may associate with hybridization incompatibility between B. napus and B. oleracea.