title: Duplication and Whorl-Specific Down-Regulation of the Obligate AP3-PI Heterodimer Genes Explain the Origin of Paeonia lactiflora Plants with Spontaneous Corolla Mutation.
abstract: Herbaceous peony (Paeonia lactiflora) is a globally important ornamental plant. Spontaneous floral mutations occur frequently during cultivation, and are selected as a way to release new cultivars, but the underlying evolutionary developmental genetics remain largely elusive. Here, we investigated a collection of spontaneous corolla mutational plants (SCMPs) whose other floral organs were virtually unaffected. Unlike the corolla in normal plants (NPs) that withered soon after fertilization, the transformed corolla (petals) in SCMPs was greenish and persistent similar to the calyx (sepals). Epidermal cellular morphology of the SCMP corolla was also similar to that of calyx cells, further suggesting a sepaloid corolla in SCMPs. Ten floral MADS-box genes from these Paeonia plants were comparatively characterized with respect to sequence and expression. Codogenic sequence variation of these MADS-box genes was not linked to corolla changes in SCMPs. However, we found that both APETALA3 (AP3) and PISTILLATA (PI) lineages of B-class MADS-box genes were duplicated, and subsequent selective expression alterations of these genes were closely associated with the origin of SCMPs. AP3-PI obligate heterodimerization, essential for organ identity of corolla and stamens, was robustly detected. However, selective down-regulation of these duplicated genes might result in a reduction of this obligate heterodimer concentration in a corolla-specific manner, leading to the sepaloid corolla in SCMPs, thus representing a new sepaloid corolla model taking advantage of gene duplication. Our work suggests that modifying floral MADS-box genes could facilitate the breeding of novel cultivars with distinct floral morphology in ornamental plants, and also provides new insights into the functional evolution of the MADS-box genes in plants.
authors.affiliation: State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing, China.
authors.forename: Pichang
authors.initials: P
authors.lastname: Gong
authors.affiliation: Landscape Architecture College of Beijing Forestry University, National Flower Engineering Research Center, Beijing, China.
authors.forename: Xiang
authors.initials: X
authors.lastname: Ao
authors.affiliation: Luoyang National Peony Garden, Mangshan Town, Old City District, Luoyang, China.
authors.forename: Gaixiu
authors.initials: G
authors.lastname: Liu
authors.affiliation: Landscape Architecture College of Beijing Forestry University, National Flower Engineering Research Center, Beijing, China.
authors.forename: Fangyun
authors.initials: F
authors.lastname: Cheng
authors.affiliation: State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing, China.|University of Chinese Academy of Sciences, Yuquan Road, Beijing, China.
authors.forename: Chaoying
authors.initials: C
authors.lastname: He
mesh_terms: D005075:Biological Evolution; D020440:Gene Duplication / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000235:genetics / Q000502:physiology; D020131:Genes, Duplicate / Q000235:genetics; D009154:Mutation; D029596:Paeonia / Q000145:classification / Q000235:genetics*; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics; D011485:Protein Binding / Q000235:genetics
chemical_list: D010940:Plant Proteins
keywords: Corolla development; Expressional variation; Functional evolution; MADS-box gene; Paeonia lactiflora; Protein–protein interaction