Transgene expression and root hair deformation of transgenic rice plants harbouring legume-specific Nod factor receptor genes in the presence and absence of nitrogen when inoculated with Sinorhizobium meliloti.

backgroundNitrogen-fixing symbiosis is an effect of crosstalk between legumes and rhizobia, mediated by Nod factors (NF) recognized by legume-specific nod factor (NF) receptors. Developing this symbiotic capability in cereal crops like rice is a promising strategy to reduce dependency on synthetic nitrogen fertilizers, but it is neither simple nor easy. To find whether legume-specific Nod Factor receptor genes are expressed in rice and whether they can change root hair morphology. METHODS AND

resultsWe developed transgenic rice plants harbouring two NF receptor genes, a co-receptor gene and two NF binding proteins: MtLYK3, MtNFP, MtDMI2, LjLNP, and MtSYMREM1. When transgenic rice roots were inoculated with fluorescent Sinorhizobium meliloti (S. meliloti), colonization of bacteria was observed on the root surface. Still, it was reduced significantly in the presence of nitrogen in the media. Gene expression of all the five transgenes in the S.meliloti inoculated roots increased to 3.5 fold. Root hair deformation was also observed when transgenic rice roots were treated with purified SmNod Factor (SmNF), and the presence of nitrogen in the medium reduced the root hair deformation percentage.

conclusionsThis study suggested that rice could interact with S. meliloti for colonization and gene expression and also could perceive the NF signal to deform root hair when the legume-specific NF receptor genes along with co-receptor gene and two NF binding proteins were present in the rice plant. This is an initial indication that rice roots can behave like a symbiotic legume if appropriate genes are transferred to it.