Durable panicle blast-resistance gene Pb1 encodes an atypical CC-NBS-LRR protein and was generated by acquiring a promoter through local genome duplication.
Rice blast is one of the most widespread and destructive plant diseases worldwide. Breeders have used disease resistance (R) genes that mediate fungal race-specific 'gene-for-gene' resistance to manage rice blast, but the resistance is prone to breakdown due to high pathogenic variability of blast fungus. Panicle blast 1 (Pb1) is a blast-resistance gene derived from the indica cultivar 'Modan'. Pb1-mediated resistance, which is characterized by durability of resistance and adult/panicle blast resistance, has been introduced into elite varieties for commercial cultivation. We isolated the Pb1 gene by map-based cloning. It encoded a coiled-coil-nucleotide-binding-site-leucine-rich repeat (CC-NBS-LRR) protein. The Pb1 protein sequence differed from previously reported R-proteins, particularly in the NBS domain, in which the P-loop was apparently absent and some other motifs were degenerated. Pb1 was located within one of tandemly repeated 60-kb units, which presumably arose through local genome duplication. Pb1 transcript levels increased during the development of Pb1+ cultivars; this expression pattern accounts for their adult/panicle resistance. Promoter:GUS analysis indicated that genome duplication played a crucial role in the generation of Pb1 by placing a promoter sequence upstream of its coding sequence, thereby conferring a Pb1-characteristic expression pattern to a transcriptionally inactive 'sleeping' resistance gene. We discuss possible determinants for the durability of Pb1-mediated blast resistance.
Hayashi
Nagao
N
Plant Disease Resistance Research Unit, Division of Plant Sciences, National Institute of Agrobiological Sciences, Kannondai 2-1-2, Tsukuba, Ibaraki 305-8602, Japan.
Inoue
Haruhiko
H
Kato
Takahiro
T
Funao
Taketo
T
Shirota
Masaki
M
Shimizu
Takehiko
T
Kanamori
Hiroyuki
H
Yamane
Hiroko
H
Hayano-Saito
Yuriko
Y
Matsumoto
Takashi
T
Yano
Masahiro
M
Takatsuji
Hiroshi
H
D000595:Amino Acid Sequence; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D019143:Evolution, Molecular; D020440:Gene Duplication; D018745:Genome, Plant; D007113:Immunity, Innate; D000090263:Leucine-Rich Repeat Proteins; D008969:Molecular Sequence Data; D012275:Oryza / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D010935:Plant Diseases / Q000235:genetics; D057865:Plant Immunity; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D018749:RNA, Plant / Q000235:genetics
D000090263:Leucine-Rich Repeat Proteins; D010940:Plant Proteins; D011506:Proteins; D018749:RNA, Plant