Asymmetric Divergence in Transmitted SNPs of DNA Replication/ Transcription and Their Impact on Gene Expression in Polyploid Brassica napus Minqiang Tang 1 , Juanling Li 1 , Xu Hu 1 , Lu Sun 1 , MMU Helal 2 , Jianguo Chen 3 * and Yuanyuan Zhang 2 * 1 Key Laboratory of Germplasm Innovation of Tropical Special Forest Trees and Ornamental Plants (Ministry of Education), College of Forestry, Hainan University, Haikou, China, 2 The Key Laboratory of Biology and Genetic Improvement of Oil Crops, The Ministry of Agriculture, Oil Crops Research Institute of Chinese, Academy of Agricultural Sciences, Wuhan, China, 3 School of Life Sciences, Hubei University, Wuhan, China The marked increase in plant genomic data has provided valuable resources for investigating the dynamic evolution of duplicate genes in polyploidy. Brassica napus is an ideal model species for investigating polyploid genome evolution. The present study comprehensively analyzed DNA and RNA variation of two representative B. napus inbredlines, Zhongshuang11 and Zhongyou821, and we investigated gene expression levels of A n and C n subgenomes in multiple tissues of the two lines. The distribution of transmitted single nucleotide polymorphisms (SNPs) was significantly different in two subgenomes of B. napus. Gene expression levels were significantly negatively correlated with number of variations in replication and transcription of the corresponding genes, but were positively correlated with the ratios of transmitted SNPs from DNA to RNA. We found a higher density of SNP variation in A n than that in C n during DNA replication and more SNPs were transmitted to RNA during transcription, which may contribute to A n expression dominance. These activities resulted in asymmetrical gene expression in polyploid B. napus. The SNPs transmitted from DNA to RNA could be an important complement feature in comparative genomics, and they may play important roles in asymmetrical genome evolution in polyploidy. Keywords: polyploidization, gene expression dominance, asymmetrical evolution, Brassica napus, transmitted variation INTRODUCTION Polyploidy is an important part of the history of natural plant species, and has promoted the domestication of cultivated crop species (Chen et al., 2018). Genome sequencing and comparative genomic analysis have identified ∼50 polyploidization events across plant phylogenetic trees to date (Vanneste et al., 2014; Van de Peer et al., 2017; Chen et al., 2018). Polyploidization is considered the primary driver of plant species diversification and plays an important role in plant genome evolution. Polyploidy has become a popular research topic in plant science due to the increased number of polyploidization events identified in plants. Subgenome dominance, defined as gene fractionation Edited by: Lidan Sun, Beijing Forestry University, China Reviewed by: Qing-Yong Yang, Huazhong Agricultural University, China Yang Xiang, Guizhou Academy of Agricultural Sciences (CAAS), China *Correspondence: Yuanyuan Zhang zhangyy@caas.cn Jianguo Chen chenjg23@hotmail.com Specialty section: This article was submitted to Plant Genomics, a section of the journal Frontiers in Genetics Received: 10 August 2021 Accepted: 18 October 2021 Published: 11 November 2021 Citation: Tang M, Li J, Hu X, Sun L, Helal MMU, Chen J and Zhang Y (2021) Asymmetric Divergence in Transmitted SNPs of DNA Replication/ Transcription and Their Impact on Gene Expression in Polyploid Brassica napus. Front. Genet. 12:756172. doi: 10.3389/fgene.2021.756172 Frontiers in Genetics | www.frontiersin.org November 2021 | Volume 12 | Article 756172 1 ORIGINAL RESEARCH published: 11 November 2021 doi: 10.3389/fgene.2021.756172