Os04g0401000

Os04g0401000 is known as Pyricularia oryzae resistance-21(Pi-21) gene.It is quantitative trait loci (QTLs) conferring field resistance to rice blast.

Annotated Information

Function

Figure 1. The introgressions on chromosome 4 from Owarihatamochi in two BC1 F1 plants, 96BC131 (A) and 96BC122 (B), respectively. (from reference).

Pi21 was identifed in Owarihatamochi (Japanese upland rice).The resistance gene, designated pi21, was mapped on chromosome 4 as a single recessive gene between RFLP marker loci G271 and G317 at a distance of 5.0 cM and 8.5 cM, respectively,using RFLP and SSR markers. The location of Pi21 is showed on the right.

Figure 2. Phenotypic characterization of the resistant pi21 allele.(from reference).

Pi21 encodes a proline-rich protein that includes a putative heavy metal–binding domain and putative protein-protein interaction motifs. Wild-type Pi21 appears to slow the plant’s defense responses, which may support optimization of defense mechanisms. Deletions in its proline-rich motif inhibit this slowing. Pi21 is separable from a closely linked gene conferring poor flavor. The resistant pi21 allele, which is found in some strains of japonica rice, could improve blast resistance of rice worldwide. Leaves of AA-pi21, a near-isogenic line (NIL) carrying Pi21 in the genetic background of a susceptible cultivar, had smaller lesions than did the susceptible cultivar (AA) in both a field evaluation and a greenhouse inoculation test. The resistant Pi21 allele had a consistent effect against all 10 of the widely distributed races of studied, although the resistance was incomplete as compared with that triggered by R genes.Histological examination showed that cells infected with a virulent race were still alive and intact in both AA and AA-pi21 40 hours after inoculation, in contrast to those infected with an avirulent race, which induces R gene–dependent hypersensitive cell death. However, cytoplasmic granules, the first sign of cell death, were frequently observed in AA-pi21 96 hours after inoculation .The rate of penetration of hyphae into host cells in AA-pi21 did not differ from that in AA, but the rate of invasion of hyphae from penetrated cells into adjacent cells, as an indicator of hyphal growth, was significantly lower in AA-pi21 , which is consistent with the observations in the greenhouse inoculation test. These observations suggest that Pi21 confers non–race-specific resistance, which is possibly associated with a slow induction of resistance.The resistant Pi21 allele did not affect resistance to other fungal and bacterial pathogens.

Figure 3. Genetic and physical maps of Pi21.(from reference).

Expression

The full lenth of　cDNA of wild-type Pi21 is 1109bp, which includes 3 exons，Encoding a proline-rich protein product of 266 amino acids containing heavy metal binding domain and protein-protein interaction domains and other functional domains. Compared with the susceptible cultivar, there are 21bp and 48bp missing of Pi21 gene in resistant varieties Owarihatamochi, which is the cause of different resistance.

Labs working on this gene

1.QTL Genomics Research Center, National Institute of Agrobiological Sciences, Kannondai 2-1-2, Tsukuba, Ibaraki 3058602, Japan.

2.Mountainous Region Agricultural Research Institute, Aichi Agricultural Research Center, Inahasi, Toyota, Aichi 4412513, Japan.

3Bioproduction Sciences, Ishikawa Prefectural University, Suematsu 1-308, Nonoichi-machi, Ishikawa 921-8836, Japan.

4.Institute of the Society for Techno-Innovation of Agriculture, Forestry and Fisheries, Ippaizuka, Tsukuba, Ibaraki 3050854, Japan.

5.Division of Plant Sciences, National Institute of Agrobiological Sciences, Kannondai 2-1-2, Tsukuba, Ibaraki 3058602, Japan.

6.Division of Genome and Biodiversity Research, National Institute of Agrobiological Sciences, Kannondai 2-1-2,Tsukuba, Ibaraki 305-8602, Japan.

7.Graduate School of Life and Environmental Sciences, University of Tsukuba, Tennohdai 1-1-1, Tsukuba, Ibaraki 305-8572, Japan.