Characterization of rice mutants with enhanced susceptibility to rice blast.
As a first step towards identifying genes involving in the signal transduction pathways mediating rice blast resistance, we isolated 3 mutants lines that showed enhanced susceptibility to rice blast KJ105 (91-033) from a T-DNA insertion library of the japonica rice cultivar, Hwayeong. Since none of the susceptible phenotypes co-segregated with the T-DNA insertion we adapted a map-based cloning strategy to isolate the gene(s) responsible for the enhanced susceptibility of the Hwayeong mutants. A genetic mapping population was produced by crossing the resistant wild type Hwayeong with the susceptible cultivar, Nagdong. Chi-square analysis of the F2 segregating population indicated that resistance in Hwayeong was controlled by a single major gene that we tentatively named Pi-hy. Randomly selected susceptible plants in the F2 population were used to build an initial map of Pi-hy. The SSLP marker RM2265 on chromosome 2 was closely linked to resistance. High resolution mapping using 105 F2 plants revealed that the resistance gene was tightly linked, or identical, to Pib, a resistance gene with a nucleotide binding sequence and leucine-rich repeats (NB-LRR) previously isolated. Sequence analysis of the Pib locus amplified from three susceptible mutants revealed lesions within this gene, demonstrating that the Pi-hy gene is Pib. The Pib mutations in 1D-22-10-13, 1D-54-16-8, and 1C-143-16-1 were, respectively, a missense mutation in the conserved NB domain 3, a nonsense mutation in the 5th LRR, and a nonsense mutation in the C terminus following the LRRs that causes a small deletion of the C terminus. These findings provide evidence that NB domain 3 and the C terminus are required for full activity of the plant R gene. They also suggest that alterations of the resistance gene can cause major differences in pathogen specificity by affecting interactions with an avirulence factor.
Kim
Hye-Kyung
HK
Plant Metabolism Research Center and Graduate School of Biotechnology, Kyung Hee University, Yongin 449-701, Korea.
Lee
Sang-Kyu
SK
Cho
Jung-Il
JI
Lee
Sichul
S
An
Gynheung
G
Jwa
Nam-Soo
NS
Kim
Byung-Ryun
BR
Cho
Young-Chan
YC
Han
Seong-Sook
SS
Bhoo
Seong-Hee
SH
Lee
Youn-Hyung
YH
Hong
Yeon-Kyu
YK
Yi
Gihwan
G
Park
Dae-Sup
DS
Hahn
Tae-Ryong
TR
Jeon
Jong-Seong
JS
D002352:Carrier Proteins / Q000235:genetics*; D032461:Chromosomes, Plant; D018744:DNA, Plant / Q000235:genetics; D004198:Disease Susceptibility; D005819:Genetic Markers; D007113:Immunity, Innate; D009154:Mutation / Q000235:genetics*; D012275:Oryza / Q000235:genetics* / Q000382:microbiology*; D028044:Phosphate-Binding Proteins; D010935:Plant Diseases / Q000235:genetics* / Q000382:microbiology; D010940:Plant Proteins / Q000235:genetics*; D030821:Plants, Genetically Modified
D002352:Carrier Proteins; D018744:DNA, Plant; D005819:Genetic Markers; D028044:Phosphate-Binding Proteins; C121462:Pib protein, Oryza sativa; D010940:Plant Proteins