Long-distance root-to-shoot transport of phytochelatins and cadmium in Arabidopsis

Proc Natl Acad Sci U S A. 2003 Aug 19;100(17):10118-23. doi: 10.1073/pnas.1734072100. Epub 2003 Aug 8.

Abstract

Phytochelatin synthases (PCS) mediate cellular heavy-metal resistance in plants, fungi, and worms. However, phytochelatins (PCs) are generally considered to function as intracellular heavy-metal detoxification mechanisms, and whether long-distance transport of PCs occurs during heavy-metal detoxification remains unknown. Here, wheat TaPCS1 cDNA expression was either targeted to Arabidopsis roots with the Arabidopsis alcohol dehydrogenase (Adh) promoter (Adh::TaPCS1/cad1-3) or ectopically expressed with the cauliflower mosaic virus 35S promoter (35S::TaPCS1/cad1-3) in the PC-deficient mutant cad1-3. Adh::TaPCS1/cad1-3 and 35S::TaPCS1/cad1-3 complemented the cadmium, mercury, and arsenic sensitivities of the cad1-3 mutant. Northern blot, RT-PCR, and Western blot analyses showed Adh promoter-driven TaPCS1 expression only in roots and thus demonstrated lack of long-distance TaPCS1 mRNA and protein transport in plants. Fluorescence HPLC analyses showed that under Cd2+ stress, no PCs were detectable in cad1-3. However, in Adh::TaPCS1/cad1-3 plants, PCs were detected in roots and in rosette leaves and stems. Inductively coupled plasma atomic emission spectrometer analyses showed that either root-specific or ectopic expression of TaPCS1 significantly enhanced long-distance Cd2+ transport into stems and rosette leaves. Unexpectedly, transgenic expression of TaPCS1 reduced Cd2+ accumulation in roots compared with cad1-3. The reduced Cd2+ accumulation in roots and enhanced root-to-shoot Cd2+ transport in transgenic plants were abrogated by l-buthionine sulfoximine. The presented findings show that (i) transgenic expression of TaPCS1 suppresses the heavy-metal sensitivity of cad1-3, (ii) PCs can be transported from roots to shoots, and (iii) transgenic expression of the TaPCS1 gene increases long-distance root-to-shoot Cd2+ transport and reduces Cd2+ accumulation in roots.

Publication types

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

MeSH terms

  • Aminoacyltransferases / genetics
  • Aminoacyltransferases / metabolism
  • Arabidopsis / drug effects
  • Arabidopsis / genetics
  • Arabidopsis / metabolism*
  • Biological Transport, Active / drug effects
  • Buthionine Sulfoximine / pharmacology
  • Cadmium / pharmacokinetics*
  • Cadmium / toxicity
  • Drug Resistance
  • Genes, Plant
  • Glutathione
  • Metalloproteins / metabolism*
  • Models, Biological
  • Mutation
  • Phytochelatins
  • Plant Roots / metabolism
  • Plant Shoots / metabolism
  • Plants, Genetically Modified

Substances

  • Metalloproteins
  • Cadmium
  • Buthionine Sulfoximine
  • Phytochelatins
  • Aminoacyltransferases
  • glutathione gamma-glutamylcysteinyltransferase
  • Glutathione