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Article|01 Feb 2020|OPEN
KSN heterozygosity is associated with continuous flowering of Rosa rugosa Purple branch
Mengjuan Bai1, Jinyi Liu1, Chunguo Fan1, Yeqing Chen1, Hui Chen1, Jun Lu1, Jingjing Sun1, Guogui Ning2 & Changquan Wang1,
1College of Horticulture, Nanjing Agricultural University, Nanjing 210095, China
2College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan 430070, China

Horticulture Research 8,
Article number: 26 (2021)
doi: 10.1038/hortres.2021.26
Views: 274

Received: 24 Jul 2020
Revised: 10 Oct 2020
Accepted: 13 Oct 2020
Published online: 01 Feb 2020

Abstract

Rose (Rosa spp.) plants flower via two contrasting methods: once flowering (OF) and continuous flowering (CF). Purple branch is a rare continuously flowering variety of Rosa rugosa that is extensively cultivated in China. However, the genetic basis of its CF behavior is unknown. We demonstrated that Purple branch is heterozygous for the TFL1homolog KSN. One KSN allele with a 9 kb Copia insertion was found to be identical to that from continuously flowering Rosa chinensis Old blush. The other allele was found to be a functional wild-type allele. The overall expression of KSN was closely linked to the floral transition, and it was significantly repressed in continuously flowering Purple branch compared with OF Plena. The promoter region of the normal KSN allele was hypermethylated, and histone methylation at H3H4, H3K9, and H3K27 of the KSN gene locus was modified in continuously flowering Purple branch. Silencing of the DNA methyltransferase genes MET1 and CMT3 and the histone methyltransferase gene SUVR5 in Purple branch led to enhanced KSN expression, but silencing of the histone demethylase gene JMJ12 suppressed KSN expression. Therefore, the CF habit of Purple branch may be due to reduced expression of KSN caused by the halved dose and may be associated with epigenetic modifications together with retrotransposon insertions along the chromosome. Our study revealed a novel mechanism underlying the CF behavior of rose plants.