AtHsp70-15-deficient Arabidopsis plants are characterized by reduced growth, a constitutive cytosolic protein response and enhanced resistance to TuMV

Plant J. 2011 Jun;66(6):983-95. doi: 10.1111/j.1365-313X.2011.04558.x. Epub 2011 Apr 28.

Abstract

Arabidopsis thaliana contains 18 genes encoding Hsp70s. This heat shock protein superfamily is divided into two sub-families: DnaK and Hsp110/SSE. In order to functionally characterize members of the Hsp70 superfamily, loss-of-function mutants with reduced cytosolic Hsp70 expression were studied. AtHsp70-1 and AtHsp70-2 are constitutively expressed and represent the major cytosolic Hsp70 isoforms under ambient conditions. Analysis of single and double mutants did not reveal any difference compared to wild-type controls. In yeast, SSE protein has been shown to act as a nucleotide exchange factor, essential for Hsp70 function. To test whether members of the Hsp110/SSE sub-family serve essential functions in plants, two members of the sub-family, AtHsp70-14 and AtHsp70-15, were analysed. Both genes are highly homologous and constitutively expressed. Deficiency of AtHsp70-15 but not of AtHsp70-14 led to severe growth retardation. AtHsp70-15-deficient plants were smaller than wild-type and exhibited a slightly different leaf shape. Stomatal closure under ambient conditions and in response to ABA was impaired in the AtHsp70-15 transgenic plants, but ABA-dependent inhibition of germination was not affected. Heat treatment of AtHsp70-15-deficient plants resulted in drastically increased mortality, indicating that AtHsp70-15 plays an essential role during normal growth and in the heat response of Arabidopsis plants. AtHsp70-15-deficient plants are more tolerant to infection by turnip mosaic virus. Comparative transcriptome analysis revealed that AtHsp70-15-deficient plants display a constitutive stress response similar to the cytosolic protein response. Based on these results, AtHsp70-15 is likely to be a key factor in proper folding of cytosolic proteins, and may function as nucleotide exchange factor as proposed for yeast.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Abscisic Acid / pharmacology
  • Arabidopsis / genetics
  • Arabidopsis / growth & development
  • Arabidopsis / physiology*
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Chromosomes, Plant / genetics
  • Cytosol / metabolism
  • Gene Expression Profiling
  • Gene Knockout Techniques
  • Gene Silencing
  • Genotype
  • Germination
  • HSP70 Heat-Shock Proteins / genetics
  • HSP70 Heat-Shock Proteins / metabolism*
  • Hot Temperature
  • Immunity, Innate*
  • Mutation
  • Phenotype
  • Plant Diseases / immunology
  • Plant Diseases / virology
  • Plant Leaves / growth & development
  • Plant Leaves / metabolism
  • Plant Stomata / drug effects
  • Plant Stomata / physiology
  • Plants, Genetically Modified / drug effects
  • Plants, Genetically Modified / growth & development
  • Plants, Genetically Modified / physiology
  • Potyvirus / immunology
  • Potyvirus / pathogenicity
  • Protein Isoforms / metabolism
  • Recombinant Fusion Proteins / metabolism
  • Tobacco / genetics
  • Tobacco / metabolism
  • Tobacco / physiology
  • Up-Regulation

Substances

  • Arabidopsis Proteins
  • HSP70 Heat-Shock Proteins
  • Protein Isoforms
  • Recombinant Fusion Proteins
  • Abscisic Acid