Paralogous SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) genes differentially regulate leaf initiation and reproductive phase change in petunia

Planta. 2016 Feb;243(2):429-40. doi: 10.1007/s00425-015-2413-2. Epub 2015 Oct 7.


Duplicated petunia clade-VI SPL genes differentially promote the timing of inflorescence and flower development, and leaf initiation rate. The timing of plant reproduction relative to favorable environmental conditions is a critical component of plant fitness, and is often associated with variation in plant architecture and habit. Recent studies have shown that overexpression of the microRNA miR156 in distantly related annual species results in plants with perennial characteristics, including late flowering, weak apical dominance, and abundant leaf production. These phenotypes are largely mediated through the negative regulation of a subset of genes belonging to the SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) family of transcription factors. In order to determine how and to what extent paralogous SPL genes have partitioned their roles in plant growth and development, we functionally characterized petunia clade-VI SPL genes under different environmental conditions. Our results demonstrate that PhSBP1and PhSBP2 differentially promote discrete stages of the reproductive transition, and that PhSBP1, and possibly PhCNR, accelerates leaf initiation rate. In contrast to the closest homologs in annual Arabidopsis thaliana and Mimulus guttatus, PhSBP1 and PhSBP2 transcription is not mediated by the gibberellic acid pathway, but is positively correlated with photoperiod and developmental age. The developmental functions of clade-VI SPL genes have, thus, evolved following both gene duplication and speciation within the core eudicots, likely through differential regulation and incomplete sub-functionalization.

Keywords: Flowering; Paralogs; Petunia; Plastochron; Virus-induced gene silencing (VIGS).

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Gene Expression Regulation, Plant
  • Gibberellins / pharmacology
  • Petunia / drug effects
  • Petunia / genetics*
  • Petunia / growth & development
  • Phylogeny
  • Plant Leaves / drug effects
  • Plant Leaves / genetics
  • Plant Leaves / growth & development
  • Plant Proteins / genetics
  • Plant Proteins / metabolism
  • Plant Proteins / physiology*
  • Reproduction / genetics
  • Transcription Factors / genetics
  • Transcription Factors / metabolism
  • Transcription Factors / physiology*


  • Gibberellins
  • Plant Proteins
  • Transcription Factors
  • gibberellic acid