title: Role of vernalization-mediated demethylation in the floral transition of Brassica rapa.
abstract: Vernalization-mediated demethylation of BrCKA2 (casein kinase II α-subunit) and BrCKB4 (casein kinase II β-subunit) shorten the period of the clock gene BrCCA1 (circadian clock associated 1) in Brassica rapa. Photoperiod and vernalization are two environmental cues involved in the regulation of floral transition, but the ways in which they interact remain unclear. DNA methylation is one of the main mechanisms involved in controlling the functional state of chromatin and gene expression in response to environmental signals. To study the interaction between photoperiod and vernalization in floral transition, we carried out a comparative genomic analysis of genome-wide DNA methylation profiles in normal (CK) and vernalized (CA) leaves from Brassica rapa using methylated-DNA immunoprecipitation sequencing (MeDIP-seq). Two subunits of casein kinase II (CK2), BrCKA2 (catalytic α-subunit of CK2) and BrCKB4 (regulatory β-subunit of CK2), exhibited gradual DNA demethylation and increased expression in vernalized B. rapa. DNA methylation-defective plants demonstrated the causal link between DNA demethylation changes and changes in gene expression. Virus-induced gene silencing (VIGS) of BrCKA2 and BrCKB4 in B. rapa resulted in no change to the period of BrCCA1 (circadian clock associated 1) and a 1-week late flowering time. Finally, we demonstrated that increased levels of BrCKA2 and BrCKB4 in vernalized B. rapa confer elevated CK2 activity, resulting in a shortened period of the clock gene BrCCA1, which plays an important role in perceiving photoperiod in plants. Thus, our results suggest that there is a direct interaction between photoperiod and vernalization through DNA methylation mechanisms.
authors.affiliation: State Key Laboratory of Crop Genetics and Germplasm Enhancement, Key Laboratory of Biology and Germplasm Enhancement of Horticultural Crops in East China, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China.
authors.forename: Weike
authors.initials: W
authors.lastname: Duan
authors.affiliation: College of LIFE Sciences, Huaibei Normal University, Huaibei, 235000, China.
authors.forename: Huijun
authors.initials: H
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Crop Genetics and Germplasm Enhancement, Key Laboratory of Biology and Germplasm Enhancement of Horticultural Crops in East China, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China.
authors.forename: Bei
authors.initials: B
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Crop Genetics and Germplasm Enhancement, Key Laboratory of Biology and Germplasm Enhancement of Horticultural Crops in East China, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China.
authors.forename: Xiaoting
authors.initials: X
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Crop Genetics and Germplasm Enhancement, Key Laboratory of Biology and Germplasm Enhancement of Horticultural Crops in East China, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China.
authors.forename: Shuaixu
authors.initials: S
authors.lastname: Shao
authors.affiliation: State Key Laboratory of Crop Genetics and Germplasm Enhancement, Key Laboratory of Biology and Germplasm Enhancement of Horticultural Crops in East China, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Li
authors.affiliation: State Key Laboratory of Crop Genetics and Germplasm Enhancement, Key Laboratory of Biology and Germplasm Enhancement of Horticultural Crops in East China, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China.
authors.forename: Xilin
authors.initials: X
authors.lastname: Hou
authors.affiliation: State Key Laboratory of Crop Genetics and Germplasm Enhancement, Key Laboratory of Biology and Germplasm Enhancement of Horticultural Crops in East China, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China. liutk@njau.edu.cn.
authors.forename: Tongkun
authors.identifier: http://orcid.org/0000-0003-4625-9248
authors.initials: T
authors.lastname: Liu
mesh_terms: D029741:Brassica rapa / Q000235:genetics* / Q000502:physiology*; D019175:DNA Methylation / Q000235:genetics*; D035264:Flowers / Q000235:genetics* / Q000502:physiology*; D017440:Photoperiod; D010940:Plant Proteins / Q000378:metabolism
chemical_list: D010940:Plant Proteins
keywords: DNA methylation; MeDIP-seq; Photoperiod; Vernalization