Arabidopsis ROP1 and ROP6 influence germination time, root morphology, the formation of F-actin bundles, and symbiotic fungal interactions

Mol Plant. 2013 May;6(3):872-86. doi: 10.1093/mp/sss101. Epub 2012 Nov 1.


The RHO-related GTPases ROP1 and ROP6 and the ROP1-interacting protein RIC4 in Arabidopsis are involved in various processes of F-actin dynamics, cell growth, and plant/microbe interactions. The knockout rop1 and rop1 rop6 seeds germinate earlier and are impaired in root hair development. Also root hair branching is strongly affected by manipulation of the RHO-related GTPase (ROP) levels. Furthermore, in the double knockout line rop1 rop6, no actin bundle formation can be detected. We demonstrate that these proteins are required for establishing a mutualistic interaction between the root-colonizing endophytic fungus Piriformospora indica and Arabidopsis. The fungus promotes growth of wild-type plants. rop1, rop6, rop1 rop6, ric4, 35S::ROP1, and 35S::ROP6 seedlings are impaired in the response to the fungus. Since the different root architectures have no effect on root colonization, the impaired response to P. indica should be caused by ROP-mediated events in the root cells. In wild-type roots, P. indica stimulates the formation of F-actin bundles and this does not occur in the rop1 rop6 knockout line. Furthermore, the fungus stimulates the expression of the calmodulin-binding protein gene Cbp60g, and this response is severely reduced in the rop mutants. We propose that ROP1 and ROP6 are required for F-actin bundle formation in the roots, which is required for P. indica-mediated growth promotion in Arabidopsis.

Keywords: Cbp60g; F-actin; GTPases; Piriformospora indica; ROP; cytoskeleton.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / metabolism*
  • Arabidopsis / anatomy & histology
  • Arabidopsis / genetics
  • Arabidopsis / growth & development
  • Arabidopsis / microbiology*
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Basidiomycota / physiology*
  • Calcium / metabolism
  • Colony Count, Microbial
  • GTP-Binding Proteins / genetics
  • GTP-Binding Proteins / metabolism*
  • Gene Expression Regulation, Plant
  • Gene Knockout Techniques
  • Genes, Plant / genetics
  • Germination*
  • Hydrogen Peroxide / metabolism
  • Monomeric GTP-Binding Proteins / genetics
  • Monomeric GTP-Binding Proteins / metabolism*
  • Mutation / genetics
  • Plant Roots / anatomy & histology*
  • Plant Roots / genetics
  • Plant Roots / growth & development
  • Plant Roots / microbiology
  • Plants, Genetically Modified
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Seeds / growth & development
  • Seeds / metabolism
  • Seeds / microbiology
  • Soil
  • Symbiosis / physiology*
  • Time Factors


  • Actins
  • Arabidopsis Proteins
  • RNA, Messenger
  • ROP6 protein, Arabidopsis
  • Soil
  • Hydrogen Peroxide
  • GTP-Binding Proteins
  • ROP1 protein, Arabidopsis
  • Monomeric GTP-Binding Proteins
  • Calcium