Genomic study of hybridization and introgression between two annual plant species
(2021)
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- Authors
- Supervisors
- Wesselingh, Renate
- Abstract
- The general framework of this work is study of hybridization between two Rhinanthus species (Orobanchaceae), Rhinanthus minor L. and Rhinanthus major using advanced genomics tools. These species are annual hemi-parasitic plants in which hybridization and introgression have been documented before. In naturally mixed populations of both species, hybridization leads predominantly to introgression from R. minor into R. major. Furthermore, hybrids with R. major as the maternal parent (F1a) have often been reported to have low germination rates in comparison with hybrids with R. minor as maternal parent (F1m). Therefore, in order to better estimate the degree of introgression between both species, a large panel of SNP markers was developed in this thesis project and used on samples collected from several mixed populations. In order to understand the mechanisms behind the low germination rate of F1a seeds, a differential gene expression study was conducted during dormancy and germination. Using ddRAD sequencing nearly 1100 species-specific SNP markers were obtained for both species and tracked in nine mixed populations from Belgium and the Netherlands. Introgression was much more frequent than could be detected with previously used ISSR and RAPD makers. Further investigation of our species-specific markers in R. major individuals with a low admixture rate with R. minor showed that only a few of the loci tended to introgress frequently, while the others had low introgression rates. Although with ddRAD sequencing we only covered a small part of the genome, we were still able to find similarity and dissimilarity of introgressed loci among the populations. Using RNA-seq in F1a and F1m seeds during cold stratification and after germination revealed that there were large transcriptome differences between seeds with different maternal plants, but we could not detect any differentially expressed genes in the plastid genome, what would be expected in case of a nuclear-cytoplasmic incompatibility. In F1m seeds, genes active in the development of seeds and seedlings were upregulated, but in F1a seeds, upregulation of genes related to stress and enduring dormancy were observed. The main cause of this maternal effect is still unclear and further investigation is needed to find out how these differences in gene expression are caused. The combined action of this thesis has opened the way towards a full understanding of hybridization and introgression between R. major and R. minor.
- Affiliations
Citations
Mirzaei, K. (2021). Genomic study of hybridization and introgression between two annual plant species. https://hdl.handle.net/2078.5/110482