High-Frequency Homologous Recombination Occurred Preferentially in Populus

Xining Geng; Yufei Xia; Hao Chen; Kang Du; Jun Yang; Xiangyang Kang

doi:10.3389/fgene.2021.703077

High-Frequency Homologous Recombination Occurred Preferentially in Populus

Front Genet. 2021 Aug 19:12:703077. doi: 10.3389/fgene.2021.703077. eCollection 2021.

Authors

Xining Geng^{1

2

3

4}, Yufei Xia^{2

3

4}, Hao Chen^{2

3

4}, Kang Du^{2

3

4}, Jun Yang^{2

3

4}, Xiangyang Kang^{2

3

4}

Affiliations

¹ Henan Province Key Laboratory of Germplasm Innovation and Utilization of Eco-Economic Woody Plant, Pingdingshan University, Pingdingshan, China.
² Beijing Advanced Innovation Center for Tree Breeding by Molecular Design, Beijing Forestry University, Beijing, China.
³ National Engineering Laboratory for Tree Breeding, Beijing Forestry University, Beijing, China.
⁴ Beijing Laboratory of Urban and Rural Ecological Environment, Beijing Forestry University, Beijing, China.

Abstract

Homologous recombination (HR), the most significant event in meiosis, has important implications for genetic diversity and evolution in organisms. Heteroduplex DNA (hDNA), the product of HR, can be captured by artificially induced chromosome doubling during the development of the embryo sac to inhibit postmeiotic segregation, subsequently, and hDNAs are directly detected using codominant simple sequence repeat (SSR) markers. In the present study, two hybrid triploid populations derived from doubling the chromosomes of the embryo sac induced by high temperature in Populus tomentosa served as starting materials. Eighty-seven, 62, and 79 SSR markers on chromosomes 01, 04, and 19, respectively, that were heterozygous in the maternal parent and different from the paternal parent were screened to detect and characterize the hDNA in P. tomentosa. The results showed that the hDNA frequency patterns on chromosomes changed slightly when the number of SSR primers increased. The highest hDNA frequency occurred at the adjacent terminal on chromosomes, which was slightly higher than those at the terminals in the two genotypic individuals, and the hDNA frequency gradually decreased as the locus-centromere distance decreased. With the increase in the number of SSR markers employed for detection, the number of recombination events (REs) detected significantly increased. In regions with high methylation or long terminal repeat (LTR) retrotransposon enrichment, the frequency of hDNA was low, and high frequencies were observed in regions with low sequence complexity and high gene density. High-frequency recombination occurring at high gene density regions strongly affected the association between molecular markers and quantitative trait loci (QTLs), which was an important factor contributing to the difficulty encountered by MAS in achieving the expected breeding results.

Keywords: Populus tomentosa; heteroduplex DNA; homologous recombination; molecular marker-assisted selection; recombination events.