Upregulation of tandem duplicated BoFLC1 genes is associated with the non-flowering trait in Brassica oleracea var. capitata

Abstract

The non-owering natural cabbage mutant 'nfc' was discovered from the breeding line 'T15' with normal owering characteristics. In this study, we investigated the molecular basis underlying the non-owering trait of 'nfc'. First, the 'nfc' was induced to ower using the grafting oral induction method, and three F 2 populations were generated. The owering phenotype of each F 2 population was widely distributed with non-owering individuals appearing in two populations. QTL-seq analysis detected a genomic region associated with owering date at approximately 51 Mb on chromosome 9 in two of the three F 2 populations. Subsequent validation and ne mapping of the candidate genomic region using QTL analysis identi ed the quantitative trait loci (QTL) at 50,177,696-51,474,818 bp on chromosome 9 covering 241 genes. Additionally, RNA-seq analysis of 'nfc' and 'T15' plants identi ed 36 differentially expressed genes related to owering. Based on these results, we identi ed tandem duplicated BoFLC1 genes, which are homologs of oral repressor FLOWERING LOCUS C (FLC), as the candidate genes responsible for the non-owering trait of 'nfc'. We designated the tandem duplicated BoFLC1 genes as BoFLC1a and BoFLC1b. Expression analysis revealed that the expression levels of BoFLC1a and BoFLC1b were downregulated during winter in 'T15' but were upregulated and maintained during winter in 'nfc'.Additionally, the expression level of the oral integrator BoFT was upregulated in the spring in 'T15' but hardly upregulated in 'nfc'. These results suggest that the upregulated levels of BoFLC1a and BoFLC1b contributed to the non-owering trait of 'nfc'. Key MessageTandem duplicated BoFLC1 (BoFLC1a and BoFLC1b) genes, which were identi ed as the candidate causal genes for the non-owering trait in the cabbage mutant 'nfc', were upregulated during winter in 'nfc'.