Comparison of five major trichome regulatory genes in Brassica villosa with orthologues within the Brassicaceae

PLoS One. 2014 Apr 22;9(4):e95877. doi: 10.1371/journal.pone.0095877. eCollection 2014.

Abstract

Coding sequences for major trichome regulatory genes, including the positive regulators GLABRA 1(GL1), GLABRA 2 (GL2), ENHANCER OF GLABRA 3 (EGL3), and TRANSPARENT TESTA GLABRA 1 (TTG1) and the negative regulator TRIPTYCHON (TRY), were cloned from wild Brassica villosa, which is characterized by dense trichome coverage over most of the plant. Transcript (FPKM) levels from RNA sequencing indicated much higher expression of the GL2 and TTG1 regulatory genes in B. villosa leaves compared with expression levels of GL1 and EGL3 genes in either B. villosa or the reference genome species, glabrous B. oleracea; however, cotyledon TTG1 expression was high in both species. RNA sequencing and Q-PCR also revealed an unusual expression pattern for the negative regulators TRY and CPC, which were much more highly expressed in trichome-rich B. villosa leaves than in glabrous B. oleracea leaves and in glabrous cotyledons from both species. The B. villosa TRY expression pattern also contrasted with TRY expression patterns in two diploid Brassica species, and with the Arabidopsis model for expression of negative regulators of trichome development. Further unique sequence polymorphisms, protein characteristics, and gene evolution studies highlighted specific amino acids in GL1 and GL2 coding sequences that distinguished glabrous species from hairy species and several variants that were specific for each B. villosa gene. Positive selection was observed for GL1 between hairy and non-hairy plants, and as expected the origin of the four expressed positive trichome regulatory genes in B. villosa was predicted to be from B. oleracea. In particular the unpredicted expression patterns for TRY and CPC in B. villosa suggest additional characterization is needed to determine the function of the expanded families of trichome regulatory genes in more complex polyploid species within the Brassicaceae.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Arabidopsis / genetics
  • Brassica / cytology
  • Brassica / genetics*
  • Brassica / metabolism
  • Gene Expression
  • Gene Expression Regulation, Plant
  • Genes, Plant
  • Phylogeny
  • Plant Leaves / cytology
  • Plant Leaves / genetics
  • Plant Leaves / metabolism
  • Plant Proteins / genetics*
  • Plant Proteins / metabolism
  • Sequence Homology, Amino Acid
  • Sequence Homology, Nucleic Acid
  • Transcription Factors / genetics*
  • Transcription Factors / physiology
  • Trichomes / genetics*
  • Trichomes / metabolism

Substances

  • Plant Proteins
  • Transcription Factors

Grants and funding

1. Agriculture and Agri-Food Canada, 2. Canola Council of Canada, 3. The Saskatchewan Agricultural Development Fund, and 4. The Saskatchewan Canola Development Commission. POS Bio-Sciences provided support in the form of a salary for author TSW-G, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.