Plant defensin AhPDF1.1 is not secreted in leaves but it accumulates in intracellular compartments

New Phytol. 2011 Oct;192(1):140-150. doi: 10.1111/j.1469-8137.2011.03792.x. Epub 2011 Jun 16.

Abstract

• Apart from their antifungal role, plant defensins have recently been shown to be involved in abiotic stress tolerance or in inhibition of root growth when added in plant culture medium. We studied the subcellular localization of these proteins, which may account for these different roles. • Stable and transient expression of AhPDF1.1::GFP (green fluorescent protein) fusion proteins were analysed in yeast and plants. Functional tests established that the GFP tag did not alter the action of the defensin. Subcellular localization of AhPDF1.1 was characterized: by imaging AhPDF1.1::GFP together with organelle markers; and by immunolabelling AhPDF1.1 in Arabidopsis halleri and Arabidopsis thaliana leaves using a polyclonal serum. • All our independent approaches demonstrated that AhPDF1.1 is retained in intracellular compartments on the way to the lytic vacuole, instead of being addressed to the apoplasm. • These findings challenge the commonly accepted idea of secretion of defensins. The subcellular localization highlighted in this study could partly explain the dual role of plant defensins on plant cells and is of major importance to unravel the mechanisms of action of these proteins at the cellular level.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptation, Physiological / drug effects
  • Amino Acid Sequence
  • Arabidopsis / drug effects
  • Arabidopsis / metabolism*
  • Arabidopsis / physiology
  • Arabidopsis Proteins / chemistry
  • Arabidopsis Proteins / metabolism*
  • Cell Compartmentation*
  • Cell Wall / drug effects
  • Cell Wall / metabolism
  • Chitosan / pharmacology
  • Defensins / chemistry
  • Defensins / metabolism*
  • Green Fluorescent Proteins / metabolism
  • Immunoassay
  • Intracellular Space / drug effects
  • Intracellular Space / metabolism*
  • Molecular Sequence Data
  • Nicotiana / drug effects
  • Nicotiana / metabolism
  • Plant Leaves / cytology
  • Plant Leaves / drug effects
  • Plant Leaves / metabolism*
  • Protein Sorting Signals
  • Protein Transport / drug effects
  • Recombinant Fusion Proteins / metabolism
  • Saccharomyces cerevisiae / drug effects
  • Saccharomyces cerevisiae / metabolism
  • Structure-Activity Relationship
  • Subcellular Fractions / drug effects
  • Subcellular Fractions / metabolism
  • Vacuoles / drug effects
  • Vacuoles / metabolism
  • Zinc / toxicity
  • trans-Golgi Network / drug effects
  • trans-Golgi Network / metabolism

Substances

  • Arabidopsis Proteins
  • Defensins
  • Protein Sorting Signals
  • Recombinant Fusion Proteins
  • Green Fluorescent Proteins
  • Chitosan
  • Zinc