Fine Mapping and Transcriptome Analysis Reveal Candidate Genes Associated with Hybrid Lethality in Cabbage (Brassica Oleracea).

Zhiliang Xiao,Yang Hu,Zezhou Liu,Zhansheng Li,Limei Yang,Xiaoli Zhang,Honghao Lv,Xing Liu,Yumei Liu,Zhiyuan Fang,Yuqian Xue,Mu Zhuang,Yangyong Zhang

doi:10.3390/genes8060147

Zhiliang Xiao, Yang Hu + Show 11 more

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https://doi.org/10.3390/genes8060147

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Abstract

Hybrid lethality is a deleterious phenotype that is vital to species evolution. We previously reported hybrid lethality in cabbage (Brassica oleracea) and performed preliminary mapping of related genes. In the present study, the fine mapping of hybrid lethal genes revealed that BoHL1 was located on chromosome C1 between BoHLTO124 and BoHLTO130, with an interval of 101 kb. BoHL2 was confirmed to be between insertion-deletion (InDels) markers HL234 and HL235 on C4, with a marker interval of 70 kb. Twenty-eight and nine annotated genes were found within the two intervals of BoHL1 and BoHL2, respectively. We also applied RNA-Seq to analyze hybrid lethality in cabbage. In the region of BoHL1, seven differentially expressed genes (DEGs) and five resistance (R)-related genes (two in common, i.e., Bo1g153320 and Bo1g153380) were found, whereas in the region of BoHL2, two DEGs and four R-related genes (two in common, i.e., Bo4g173780 and Bo4g173810) were found. Along with studies in which R genes were frequently involved in hybrid lethality in other plants, these interesting R-DEGs may be good candidates associated with hybrid lethality. We also used SNP/InDel analyses and quantitative real-time PCR to confirm the results. This work provides new insight into the mechanisms of hybrid lethality in cabbage.

Highlights

Hybrid lethality (HL), a postzygotic reproductive isolation phenomenon, plays important roles in species formation and integrity [1]
We further analyzed the relationship between these candidate genes and HL in cabbage. These R-differentially expressed genes (DEGs) (Bo1g153320, Bo1g153380) and R-related genes (Bo1g153250, Bo1g153280) encode the Leucine-rich repeat domain (LRR), and Rothberg et al suggested that genes containing LRRs are associated with a variety of biological processes, including disease resistance, apoptosis, and the immune response in Drosophila, and these motifs have been implicated in protein-protein interactions as part of an extracellular domain in a variety of other proteins, which is accordant with the DM model [54]; The R-DEG Bo1g173780 encodes the protein kinase-like domain, which is involved in a number of fundamental cellular processes such as apoptosis, proliferation, motility, and adhesion [55]. These results show that our candidate genes might be closely relevant to HL in cabbage, especially the R-DEGs
BoHL1 was located on chromosome C1, as indicated by InDels BoHLTO124 and BoHLTO130, with an interval between the two markers of 101 kb

Summary

Introduction

Hybrid lethality (HL), a postzygotic reproductive isolation phenomenon, plays important roles in species formation and integrity [1]. In plants, this type of genetic incompatibility occurs in the seedling or adult stage and is often associated with symptoms such as wilting, chlorosis, stunted growth, and lethality [2]. HL represents a barrier to interspecific hybridization, and remains a serious adverse event in the agricultural exploitation of wild species as a genetic resource for breeding [1,7]. Several scholars have proposed hybrid lethality genetic models. These include the Dobzhansky-Muller (DM) genetic model, which is the most widely accepted model, and a dual site

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