title: Expression of B-class MADS-box genes in response to variations in photoperiod is associated with chasmogamous and cleistogamous flower development in Viola philippica.
abstract: Some plants develop a breeding system that produces both chasmogamous (CH) and cleistogamous (CL) flowers. However, the underlying molecular mechanism remains elusive.
  
  
  
  In the present study, we observed that Viola philippica develops CH flowers with short daylight, whereas an extended photoperiod induces the formation of intermediate CL and CL flowers. In response to long daylight, the respective number and size of petals and stamens was lower and smaller than those of normally developed CH flowers, and a minimum of 14-h light induced complete CL flowers that had no petals but developed two stamens of reduced fertility. The floral ABC model indicates that B-class MADS-box genes largely influence the development of the affected two-whorl floral organs; therefore, we focused on characterizing these genes in V. philippica to understand this particular developmental transition. Three such genes were isolated and respectively designated as VpTM6-1, VpTM6-2, and VpPI. These were differentially expressed during floral development (particularly in petals and stamens) and the highest level of expression was observed in CH flowers; significantly low levels were detected in intermediate CL flowers, and the lowest level in CL flowers. The observed variations in the levels of expression after floral induction and organogenesis apparently occurred in response to variations in photoperiod.
  
  
  
  Therefore, inhibition of the development of petals and stamens might be due to the downregulation of B-class MADS-box gene expression by long daylight, thereby inducing the generation of CL flowers. Our work contributes to the understanding of the adaptive evolutionary formation of dimorphic flowers in plants.
authors.affiliation: Life Science College, Northwest Normal University, Anning East Road 967, Anning, 730070, Lanzhou, Gansu, China.
authors.forename: Qiaoxia
authors.initials: Q
authors.lastname: Li
authors.affiliation: Life Science College, Northwest Normal University, Anning East Road 967, Anning, 730070, Lanzhou, Gansu, China.
authors.forename: Qingdi
authors.initials: Q
authors.lastname: Huo
authors.affiliation: Life Science College, Northwest Normal University, Anning East Road 967, Anning, 730070, Lanzhou, Gansu, China.
authors.forename: Juan
authors.initials: J
authors.lastname: Wang
authors.affiliation: Life Science College, Northwest Normal University, Anning East Road 967, Anning, 730070, Lanzhou, Gansu, China.|State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Nanxincun 20, Xiangshan, 100093, Beijing, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Zhao
authors.affiliation: Life Science College, Northwest Normal University, Anning East Road 967, Anning, 730070, Lanzhou, Gansu, China. kunsun@163.com.
authors.forename: Kun
authors.initials: K
authors.lastname: Sun
authors.affiliation: State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Nanxincun 20, Xiangshan, 100093, Beijing, China. chaoying@ibcas.ac.cn.
authors.forename: Chaoying
authors.initials: C
authors.lastname: He
mesh_terms: D035264:Flowers / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D018506:Gene Expression Regulation, Plant / Q000235:genetics / Q000502:physiology; D017440:Photoperiod; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D032413:Viola / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
chemical_list: D010940:Plant Proteins
keywords: Adaptive evolution; Dimorphic flower; Gene expression; MADS-box gene; Photoperiod; Viola philippica