The RHO-related GTPases ROP1 and ROP6 and the ROPl-interacting protein RIC4 in Arabidopsis are involved in various processes of F-actin dynamics, cell growth, and plant/microbe interactions. The knockout ropl and ropl...The RHO-related GTPases ROP1 and ROP6 and the ROPl-interacting protein RIC4 in Arabidopsis are involved in various processes of F-actin dynamics, cell growth, and plant/microbe interactions. The knockout ropl and ropl 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 ropl 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, ropl, rop6, ropl 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 ropl 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.展开更多
文摘The RHO-related GTPases ROP1 and ROP6 and the ROPl-interacting protein RIC4 in Arabidopsis are involved in various processes of F-actin dynamics, cell growth, and plant/microbe interactions. The knockout ropl and ropl 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 ropl 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, ropl, rop6, ropl 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 ropl 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.
