Os06g0330100

Annotated Information

Introduction

More than 70 categories of rice diseases have been recorded worldwide, among them rice blast caused by the filamentous fungus Magnaporthe oryzae is the most devastating disease and has been identified in at least 85 rice growing countries (Ou, 1985; Couch and Kohn, 2002). In recent years,rice blast epidemics have been occurred in many countries especially the important rice cultivation areas such as China,Vietnam, Japan and Korea (Liu et al., 2009; Wilson and Talbot, 2009). Better understanding of the mechanisms Better understanding of the mechanisms underlying the interaction between pathogens and host plants and selection for stable resistant new varieties have been long considered as the most efficient and effective way of controlling the disease (Ahn, 1994).Pi25 the blast resistance gene,so it is important to research its founction;expression;evolution and structure.

Function

Rice blast resistance, caused by Magnaporthe grisea,has been studied extensively, Pi-25 is the main effect blast resistance gene from a stable blast resistance cultivar Gumei2, over-expression analysis and complementation test showed that Pi25 conferred blast resistance to M. oryzae isolate js001-20. It have stronger resistance to leaf blast and panicle blast to rice blast fungus strains in China 92-183 (small ZC15) and have the same allele with Pid3.

Expression

Pi25 was an intronless gene of 2772 nucleotides with single nucleotide substitution in comparison to Pid3 at the nucleotide position 459 and predicatively encoded a typical coiled coilenucleotide binding siteeleucine rich repeat (CC-NBS-LRR) protein of 924 amino acid residuals with 100% identity to Pid3 putative protein.Pi - 25 in rice chromosome's markers between A7 and RG456, 6 figure distance is 1.7 cM and 1.5 cM respectively. The susceptible allele pi25 in Nipponbare contained a nonsense mutation at the nucleotide position 2209 resulting in a truncated protein with 736 amino acid residuals. In addition, 14 nucleotide substitutions resulting in 10 amino acid substitutions were identified between Pi25 and pi25 upstream the premature stop codon in the susceptible allele. Although the mechanism of Pi25/Pid3-mediated resistance needs to be further investigated, the isolation of the allele would facilitate the utilization of Pi25/Pid3 in rice blast resistance breeding program via transgenic approach and marker assisted selection.The length of Pid3 cDNA is 2970 bp.Pid3 contains two exons and encoding a 923 amino acid composition of protein products, products containing the NBS LRR structure domain and MHD motif. Pid3Nip in the LRR structure domain. its transcription start site began to 2208th nucleotide, the CAG is replaced by the TAG. Japonica rice varieties Pid3 to pseudogenes are occurred after the process of indica japonica differentiation (Shang et al., 2009).

Evolution

Genomic location of gene Pi25 (t) conferring neck blast resistance to the Chinese isolate 92-183(race ZC 15)was verified to be located between markers A7 and RG456 on chromosome 6 with genetic distance of 1.7cM and 1.5cM to A7 and RG456 respectively.Leaf blast resistance of Gumei 2 to the Philippine isolate Ca 89(linage 4) was fpune to be controlled by a single gene. The gene tentetively designated as Pi26(t) was located between markers B10 and R674 on chromosome 6,with genetic distances of 5.7 cM and 25.8 cM to B10 and R674 respectively.Resistant alleles at both gene loci were derived from Gumei 2, indicating an existence of resistance gene cluster in Gumei 2 .

The allelic Pid3 loci in most of the tested japonica varieties were identified as pseudogenes due to a nonsense mutation at the nucleotide position 2208 starting from the translation initiation site. However, this mutation was not found in any of the tested indica varieties, African cultivated rice varieties, or AA genome-containing wild rice species. These results suggest that the pseudogenization of Pid3 in japonica occurred after the divergence of indica and japonica.

Genetic analysis indicated that the resistance to leaf blast was controlled by three genes and the presence of resistant alleles at any loci would result in resistance. One of the three genes did not have effects at the flowering stage. Two genes, tentatively assigned as Pi24(t) and Pi25(t), were mapped onto chromosome 12 and 6, respectively, based on RGA (resistance gene analog), RFLP and RAPD markers. Pi24(t) conferred resistance to leaf blast only, and its resistance allele was from Zhong 156. Pi25(t) conferred resistance to both leaf and neck blast, and its resistance allele was from Gumei 2. In a natural infection test in a blast hot-spot,Pi25(t) exhibited high resistance to neck blast, while Pi24(t) showed little effect. A set of near-isogenic lines (NILs) for rice blast resistance was previously developed in the genetic background of the indica cultivar CO 39. Allelism between the resistance genes in the CO 39 NILs and Kiyosawa's differentials was analyzed. Pi1(t) was closely linked to Pi-K on chromosome 11. Pi2(t) was allelic to Piz on chromosome 6. Pi3(t) was closely linked to Pi-i. Pi4a(t) was identical to Pita on chromosome 12. To analyze Pi5(t), Pi7(t), and Pi12(t) in a durably resistant cultivar Moroberekan, we used an approach for developing pre-isogenic lines from a recombinant inbred population that has been used for molecular mapping of those resistance genes. Pi7(t) was allelic or closely linked to Pi1. The genetic analyses of Pi5(t) and Pi12(t) are currently under way. There are six single nucleotide substitutions (g775a,t1197c,t2444a,c2566g,g2680a, and g2687a) in the cod-ing sequences between Pi25, the resistant allele from Gumei 2, and pi25, the susceptible allele from Zhongjian 100, respectively, leading to the substitution of five amino acids (V259I, F815Y, H856D, V894I, and R896Q). One of the single nucleotide polymorphisms (SNPs), t1197c, is a synonymous mutation in both alleles (Fig. 3). Among the other five SNPs, four SNPs (g775a, t2444a,c2566g, and g2687a) corresponding to four restriction endonuclease (RE) recognition sites were chosen for the development of gene specific markers. Hinc II (g775a) and Hpy 99I (g2687a) detect and digest specifically for the resistant allele Pi25 while Nde I (t2444a) and BglII (c2566g) detect and digest specifically for the susceptibleallele pi25 (Fig. 1(pi 25 locus.png)).

Labs working on this gene

Lihuang Zhu personal homepage:http://sourcedb.cas.cn/sourcedb_genetics_cas/yw/zjrc/pgr/200907/t20090721_2130981.html Jianli Wu personal home page:http://www.researchgate.net/profile/Jianli_Wu

• Chinese National Centre for Rice Improvement and State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou 310006, China.
• Zhejiang Academy of Agricultural Sciences,Huangzhou 310028,China
• State Key Laboratory of Plant Genomics and National Plant Gene Research Centre, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China.
• Biology Department, Xiamen University, Xiamen, 361005, China
• Institute of Plant Protection, Zhejiang Academy of Agricultural Sciences, Hangzhou, 310021, China
• Entomology and Plant Pathology Division, International Rice Research Institute, Philippines
• Institute of Rice Research,Hunan Province: http://changsha05927.11467.com/.

References

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 A Pid3 allele from rice cultivar Gumei2 confers resistance to Magnaporthe oryzae
 Journal of genetics and genomics, 2011, 38(5): 209-216 

2. Junjun Shang;Yong Tao;Xuewei Chen;Yan Zou;Cailin Lei;Jing Wang;Xiaobing Li;Xianfeng Zhao;Meijun Zhang;Zhike Lu;Jichen Xu;Zhukuan Cheng;Jianmin Wan;Lihuang Zhu

 Identification of a New Rice Blast Resistance Gene, Pid3, by Genomewide Comparison of Paired Nucleotide-Binding Site–Leucine-Rich Repeat Genes and Their Pseudogene Alleles Between the Two Sequenced Rice Genomes
 Genetics, 2009, 182(4): 1303-1311 

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