Map-based Cloning And Functional Study Of NRTP1, A New CC-NB-LRR Type R Gene In Rice

The nrtp1 mutant was identified initially in the heterozygous state by screening an EMS-generated population of rice cultivar kasalath. The offspring of the original mutant plant had long root like wild-type, medium root and short root there phenotypes, and the segregated ratio was 1:2:1. The root length of the homozygous mutant was deficiency of 0.5cm, and unable to survive longer than 3 weeks after germination. These observations strongly suggest that the nrtp1 phenotype segregates as a semi-dominant trait, and mutant plants are seeding-lethal in the homozygous state.Evans blue staining and resin slices of root tip revealed that there has large area of dead cells in the root tip and slide root gap. Map-based cloning revealed that NRTP1, encodes a typical CC-NB-LRR-type protein in rice, was mapped on chromosome 12. Sequence analysis revealed that a A to G point mutation was occurred at 1166 bp.The point mutation leads to a Asp to Gly transition in the non-conserved region NB domain. So we speculated that the NRTP1 may related to plant.The RT-PCR analysis of the expression of six defense-related maker genes revealed that PR10 a and PBZ1 were up-regulated in the mutant. It indicated that NRTP1 was related to disease resistance. Then we constructed over-expression, GUS and GFP fusion expression vectors, and will be helpful for the further research of the function of NRTP1.