Flower development of Phalaenopsis orchid involves functionally divergent SEPALLATA-like genes

New Phytol. 2014 May;202(3):1024-42. doi: 10.1111/nph.12723. Epub 2014 Feb 14.

Abstract

The Phalaenopsis orchid produces complex flowers that are commercially valuable, which has promoted the study of its flower development. E-class MADS-box genes, SEPALLATA (SEP), combined with B-, C- and D-class MADS-box genes, are involved in various aspects of plant development, such as floral meristem determination, organ identity, fruit maturation, seed formation and plant architecture. Four SEP-like genes were cloned from Phalaenopsis orchid, and the duplicated PeSEPs were grouped into PeSEP1/3 and PeSEP2/4. All PeSEPs were expressed in all floral organs. PeSEP2 expression was detectable in vegetative tissues. The study of protein-protein interactions suggested that PeSEPs may form higher order complexes with the B-, C-, D-class and AGAMOUS LIKE6-related MADS-box proteins to determine floral organ identity. The tepal became a leaf-like organ when PeSEP3 was silenced by virus-induced silencing, with alterations in epidermis identity and contents of anthocyanin and chlorophyll. Silencing of PeSEP2 had minor effects on the floral phenotype. Silencing of the E-class genes PeSEP2 and PeSEP3 resulted in the downregulation of B-class PeMADS2-6 genes, which indicates an association of PeSEP functions and B-class gene expression. These findings reveal the important roles of PeSEP in Phalaenopsis floral organ formation throughout the developmental process by the formation of various multiple protein complexes.

Keywords: Phalaenopsis; SEPALLATA; complex formation; divergence; flower development; orchid.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Cell Shape / genetics
  • Cloning, Molecular
  • Flowers / genetics*
  • Flowers / growth & development*
  • Flowers / ultrastructure
  • Gene Expression Profiling
  • Gene Expression Regulation, Plant
  • Gene Regulatory Networks
  • Gene Silencing
  • Genes, Plant*
  • MADS Domain Proteins / genetics
  • MADS Domain Proteins / metabolism
  • Models, Biological
  • Molecular Sequence Data
  • Orchidaceae / genetics*
  • Orchidaceae / growth & development*
  • Organ Specificity / genetics
  • Organogenesis / genetics
  • Phenotype
  • Phylogeny
  • Plant Epidermis / cytology
  • Plant Epidermis / ultrastructure
  • Plant Proteins / chemistry
  • Plant Proteins / genetics*
  • Plant Proteins / metabolism
  • Plants, Genetically Modified
  • Promoter Regions, Genetic / genetics
  • Protein Binding

Substances

  • MADS Domain Proteins
  • Plant Proteins