Cross-genome transcriptional interplay between Brassica oleracea introgressions and the Brassica rapa host
2026.11.10
Abstract
Flowering time is a critical developmental trait in plants which controlled by different pathways. Vernalization, a prolonged exposure to low temperatures, promotes flowering through epigenetic repression of FLOWERING LOCUS C (FLC), a major floral repressor. Closely related Brassica species, including Brassica rapa and Brassica oleracea, exhibit distinct vernalization responses that influence flowering behavior when genomic regions are exchanged through interspecific hybridization. In this study, we investigated the molecular effects of introducing B. oleracea genomic region into B. rapa genetic background using the chromosome segment substitution line (CSSL) #174-12-18, which carries the upper arm of chromosome C02 containing BoFLC2. Phenotypic analysis revealed that #174-12-18 exhibited a higher vernalization requirement and flowered later than the parental B. rapa cultivar ‘CR-Kanki’. Gene expression analysis showed that BoFLC2 was less effectively repressed during cold treatment compared with the endogenous BrFLC2 in ‘CR-Kanki’. Furthermore, BoFLC2 was reactivated after plants were transferred to warm conditions, suggesting unstable maintenance of cold-induced repression. Transcriptome analysis demonstrated extensive genome-wide transcriptional reprogramming in #174-12-18, after excluding genes located within the introgressed region, indicating that C02 segment has broad regulatory effects on the host genome. Most flowering-related genes showed limited expression changes; the vernalization-induced upregulation of the floral integrator BrSOC1-1 was attenuated in #174-12-18, contributing to delayed flowering. Epigenetic analysis revealed H3K27me3 accumulation at the BoFLC2 locus varied according to developmental stage and genetic background, suggesting differences in the stability of vernalization-induced silencing. Introgression of a flowering regulator-containing genomic region can alter vernalization responses and reshape transcriptional networks, providing insights for flowering-time regulation and Brassica crop improvement.
Flowering time is a critical developmental trait in plants which controlled by different pathways. Vernalization, a prolonged exposure to low temperatures, promotes flowering through epigenetic repression of FLOWERING LOCUS C (FLC), a major floral repressor. Closely related Brassica species, including Brassica rapa and Brassica oleracea, exhibit distinct vernalization responses that influence flowering behavior when genomic regions are exchanged through interspecific hybridization. In this study, we investigated the molecular effects of introducing B. oleracea genomic region into B. rapa genetic background using the chromosome segment substitution line (CSSL) #174-12-18, which carries the upper arm of chromosome C02 containing BoFLC2. Phenotypic analysis revealed that #174-12-18 exhibited a higher vernalization requirement and flowered later than the parental B. rapa cultivar ‘CR-Kanki’. Gene expression analysis showed that BoFLC2 was less effectively repressed during cold treatment compared with the endogenous BrFLC2 in ‘CR-Kanki’. Furthermore, BoFLC2 was reactivated after plants were transferred to warm conditions, suggesting unstable maintenance of cold-induced repression. Transcriptome analysis demonstrated extensive genome-wide transcriptional reprogramming in #174-12-18, after excluding genes located within the introgressed region, indicating that C02 segment has broad regulatory effects on the host genome. Most flowering-related genes showed limited expression changes; the vernalization-induced upregulation of the floral integrator BrSOC1-1 was attenuated in #174-12-18, contributing to delayed flowering. Epigenetic analysis revealed H3K27me3 accumulation at the BoFLC2 locus varied according to developmental stage and genetic background, suggesting differences in the stability of vernalization-induced silencing. Introgression of a flowering regulator-containing genomic region can alter vernalization responses and reshape transcriptional networks, providing insights for flowering-time regulation and Brassica crop improvement.
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Kaoru Tonosaki
Associate Professor
Department of Nanobioscience, Yokohama City University, Yokohama, Japan
Associate Professor
Department of Nanobioscience, Yokohama City University, Yokohama, Japan
