Eight Amino-Acid Differences Within Three Leucine-Rich Repeats Between Pi2 and Piz-t Resistance Proteins Determine the Resistance Specificity to Magnaporthe grisea

• Published in: Molecular plant-microbe interactions Vol. 19; no. 11; pp. 1216 - 1228
• Main Authors: Zhou, B, Qu, S, Liu, G, Dolan, M, Sakai, H, Lu, G, Bellizzi, M, Wang, G.L
• Format: Journal Article
• Language: English
• Published: St Paul, MN APS Press 01.11.2006; The American Phytopathological Society
• Subjects: Alleles; Amino Acid Motifs; Amino Acid Sequence; amino acid sequences; amino acids; binding sites; Biological and medical sciences; blast disease; chromosome mapping; Cloning, Molecular; disease resistance; Evolution, Molecular; Exons; Fundamental and applied biological sciences. Psychology; Fungal plant pathogens; Gene Expression; genes; Genes, Plant; genetic complementation; Genetic Complementation Test; genetic resistance; Introns; leucine; Leucine - chemistry; Leucine - physiology; leucine-rich repeats; Magnaporthe - physiology; Magnaporthe grisea; microbial genetics; Molecular Sequence Data; Mutation; nucleotide sequences; Oryza - chemistry; Oryza - genetics; Oryza - microbiology; Oryza sativa; Phytopathology. Animal pests. Plant and forest protection; Plant Diseases - genetics; Plant Diseases - microbiology; plant pathogenic fungi; plant proteins; Plant Proteins - chemistry; Plant Proteins - genetics; Plant Proteins - physiology; Plants, Genetically Modified; Repetitive Sequences, Amino Acid; resistance gene alleles; rice; strains; Monocotyledones; Plant pathogen; avirulence; Binding site; Cereal crop; Fungi; Oryza sativa; Binding protein; Specificity; Gene; Gramineae; Angiospermae; resistance gene alleles; Ascomycetes; Complementation; Thallophyta; Genetic mapping; Gene cluster; Enzyme; Transferases; Resistance; Allele; Magnaporthe grisea; Isolate; Spermatophyta; Mutation; Aminomethyltransferase; Cultivar
• ISSN: 0894-0282; 1943-7706
• DOI: 10.1094/MPMI-19-1216

The rice blast resistance (R) genes Pi2 and Piz-t confer broad-spectrum resistance against different sets of Magnaporthe grisea isolates. We first identified the Pi2 gene using a map-based cloning strategy. The Pi2 gene is a member of a gene cluster comprising nine gene members (named Nbs1-Pi2 to Nbs9-Pi2) and encodes a protein with a nucleotide-binding site and leucine-rich repeat (LRR) domain. Fine genetic mapping, molecular characterization of the Pi2 susceptible mutants, and complementation tests indicated that Nbs4-Pi2 is the Pi2 gene. The Piz-t gene, a Pi2 allele in the rice cultivar Toride 1, was isolated based on the Pi2 sequence information. Complementation tests confirmed that the family member Nbs4-Piz-t is Piz-t. Sequence comparison revealed that only eight amino-acid changes, which are confined within three consecutive LRR, differentiate Piz-t from Pi2. Of the eight variants, only one locates within the xxLxLxx motif. A reciprocal exchange of the single amino acid between Pi2 and Piz-t did not convert the resistance specificity to each other but, rather, abolished the function of both resistance proteins. These results indicate that the single amino acid in the xxLxLxx motif may be critical for maintaining the recognition surface of Pi2 and Piz-t to their respective avirulence proteins.