Response to zinc deficiency of two rice lines with contrasting tolerance is determined by root growth maintenance and organic acid exudation rates, and not by zinc-transporter activity

New Phytol. 2010 Apr;186(2):400-14. doi: 10.1111/j.1469-8137.2009.03177.x. Epub 2010 Jan 22.

Abstract

*Zinc (Zn)-deficient soils constrain rice (Oryza sativa) production and cause Zn malnutrition. The identification of Zn-deficiency-tolerant rice lines indicates that breeding might overcome these constraints. Here, we seek to identify processes underlying Zn-deficiency tolerance in rice at the physiological and transcriptional levels. *A Zn-deficiency-tolerant line RIL46 acquires Zn more efficiently and produces more biomass than its nontolerant maternal line (IR74) at low [Zn](ext) under field conditions. We tested if this was the result of increased expression of Zn(2+) transporters; increased root exudation of deoxymugineic acid (DMA) or low-molecular-weight organic acids (LMWOAs); and/or increased root production. Experiments were performed in field and controlled environment conditions. *There was little genotypic variation in transcript abundance of Zn-responsive root Zn(2+)-transporters between the RIL46 and IR74. However, root exudation of DMA and LMWOA was greater in RIL46, coinciding with increased root expression of putative ligand-efflux genes. Adventitious root production was maintained in RIL46 at low [Zn](ext), correlating with altered expression of root-specific auxin-responsive genes. *Zinc-deficiency tolerance in RIL46 is most likely the result of maintenance of root growth, increased efflux of Zn ligands, and increased uptake of Zn-ligand complexes at low [Zn](ext); these traits are potential breeding targets.

MeSH terms

  • Adaptation, Physiological* / drug effects
  • Azetidinecarboxylic Acid / analogs & derivatives
  • Azetidinecarboxylic Acid / metabolism
  • Carboxylic Acids / metabolism*
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Gene Expression Profiling
  • Gene Expression Regulation, Plant / drug effects
  • Genes, Plant / genetics
  • Inbreeding
  • Minerals / metabolism
  • Models, Biological
  • Molecular Weight
  • Oligonucleotide Array Sequence Analysis
  • Oryza / drug effects
  • Oryza / genetics
  • Oryza / growth & development*
  • Plant Proteins / genetics
  • Plant Proteins / metabolism
  • Plant Roots / drug effects
  • Plant Roots / genetics
  • Plant Roots / growth & development*
  • Plant Shoots / drug effects
  • Plant Shoots / metabolism
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • Zinc / deficiency*
  • Zinc / pharmacology

Substances

  • Carboxylic Acids
  • Carrier Proteins
  • Minerals
  • Plant Proteins
  • RNA, Messenger
  • zinc-binding protein
  • Azetidinecarboxylic Acid
  • 2'-deoxymugineic acid
  • Zinc