Identification of a new R3 MYB type repressor and functional characterization of the members of the MBW transcriptional complex involved in anthocyanin biosynthesis in eggplant (S. melongena L.)

PLoS One. 2020 May 14;15(5):e0232986. doi: 10.1371/journal.pone.0232986. eCollection 2020.

Abstract

Here we focus on the highly conserved MYB-bHLH-WD repeat (MBW) transcriptional complex model in eggplant, which is pivotal in the transcriptional regulation of the anthocyanin biosynthetic pathway. Through a genome-wide approach performed on the recently released Eggplant Genome (cv. 67/3) previously identified, and reconfirmed by us, members belonging to the MBW complex (SmelANT1, SmelAN2, SmelJAF13, SmelAN1) were functionally characterized. Furthermore, a regulatory R3 MYB type repressor (SmelMYBL1), never reported before, was identified and characterized as well. Through a qPCR approach, we revealed specific transcriptional patterns of candidate genes in different plant tissue/organs at two stages of fruit development. Two strategies were adopted for investigating the interactions of bHLH partners (SmelAN1, SmelJAF13) with MYB counterparts (SmelANT1, SmelAN2 and SmelMYBL1): Yeast Two Hybrid (Y2H) and Bimolecular Fluorescent Complementation (BiFC) in A. thaliana mesophylls protoplast. Agro-infiltration experiments highlighted that N. benthamiana leaves transiently expressing SmelANT1 and SmelAN2 showed an anthocyanin-pigmented phenotype, while their co-expression with SmelMYBL1 prevented anthocyanin accumulation. Our results suggest that SmelMYBL1 may inhibits the MBW complex via the competition with MYB activators for bHLH binding site, although this hypothesis requires further elucidation.

MeSH terms

  • Amino Acid Sequence
  • Anthocyanins / biosynthesis*
  • Basic Helix-Loop-Helix Transcription Factors / genetics
  • Basic Helix-Loop-Helix Transcription Factors / metabolism
  • Gene Expression Regulation, Plant
  • Genes, Plant
  • Genes, Regulator
  • Multigene Family
  • Nicotiana / genetics
  • Nicotiana / metabolism
  • Phylogeny
  • Plant Proteins / genetics*
  • Plant Proteins / metabolism*
  • Plants, Genetically Modified
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Repressor Proteins / genetics*
  • Repressor Proteins / metabolism*
  • Solanum melongena / genetics*
  • Solanum melongena / metabolism*

Substances

  • Anthocyanins
  • Basic Helix-Loop-Helix Transcription Factors
  • Plant Proteins
  • Recombinant Proteins
  • Repressor Proteins

Grants and funding

The authors received no specific funding for this work.