BGIOSGA036370

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Annotated Information

The rice Pita gene participate in the resistance to strains of the rice blast fungus, Magnaporthe grisea.

Function

Pi-ta in rice encodes a putative cytoplasmic receptor with a centrally localized nucleotide-binding site and leucine-rich domain (LRD) at the C-terminus.It interacts with AVR-Pita protein secreted by rice blast fungus during infection. AVR-Pita protein is predicted to encode a metalloprotease with an N-terminal secretory signal and pro-protein sequences. It binds directly to the Pi-ta LRD region inside the plant cell to initiate a Pi-ta-mediated defense responses which include a rapid, localized cell death termed the hypersensitive response (HR), production of antimicrobial compounds, lignin formation, an oxidative burst and increased expression of pathogenesis-related genes[1]. A single-copy gene, Pi-ta shows low constitutive expression in both resistant and susceptible rice. Susceptible rice varieties contain pi-ta-alleles encoding predicted proteins that share a single amino acid difference relative to the Pi-ta resistance protein: serine instead of alanine at position 918.[2] A single dominant nuclear gene Ptr(t) is required for Pi-ta–mediated signal recognition. Ptr(t) and Pi-ta,located within a 9-megabase region,are linked and cosegregate.[3]

Expression

Figure1 Disease reaction to M. grisea IK81-25 (AVR-pita) on wild rice and rice cultivars. R, resistant; S, susceptible.

Evolution

The genotype variation and resistant/susceptible phenotype at the Pi-ta locus of wild rice (Oryza rufipogon), the ancestor of cultivated rice (O. sativa), was surveyed in 36 locations worldwide to study the molecular evolution and functional adaptation of the Pi-ta gene.The low nucleotide polymorphism of the Pi-ta gene of O. rufipogon was similar to that of O. sativa, but greatly differed from what has been reported for other O. rufipogon genes. The haplotypes can be subdivided into two divergent haplogroups named H1 and H2. H1 is derived from H2, with nearly no variation and at a low frequency. H2 is common and is the ancestral form. The leucine-rich repeat (LRR) domain has a high pnon/psyn ratio, and the low polymorphism of the Pi-ta gene might have primarily been caused by recurrent selective sweep and constraint by other putative physiological functions. Meanwhile, we provide data to show that the amino acid Ala-918 of H1 in the LRR domain has a close relationship with the resistant phenotype. H1 might have recently arisen during rice domestication and may be associated with the scenario of a blast pathogen–host shift from Italian millet to rice[4].

Figure2 Geographic distributions of the surveyed haplogroups of the O. rufipogon and O. bathii accessions.

Figure3 Maximum-likelihood tree of the complete DNA sequence of Pi-ta alleles. The O. barthii sequence was used as the outgroup. Bootstrap proportions of 1000 bootstrap replicates >65 are indicated above the branches. Solid boxes mark alleles that might have been caused by admixture. The shaded clade highlights alleles with the Ala-918 amino acid. Shaded boxes are alleles of O. sativa. H1, haplogroup H1; H2, haplogroup H2; H-OB, haplogroup of O. barthii. The rice cultivar abbreviations are the same as those given in the legend to Figure 3.

Labs working on this gene

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References

[1] Yulin Jia;Sean A. McAdams;Gregory T. Bryan;Howard P. Hershey;Barbara Valent. Direct interaction of resistance gene and avirulence gene products confers rice blast resistance. The EMBO Journal, 2000, 19(15): 4004-4014

[2] Gregory T. Bryan;Kun-Sheng Wu;Leonard Farrall;Yulin Jia;Howard P. Hershey;Sean A. McAdams;Kristina N. Faulk;Gail K. Donaldson;Renato archini;Barbara Valent. A Single Amino Acid Difference Distinguishes Resistant and Susceptible Alleles of the Rice Blast Resistance Gene Pi-ta. The Plant Cell, 2000, 12(11): 2033-2046

[3] Yulin Jia;Rodger Martin. Identification of a New Locus, Ptr(t), Required for Rice Blast Resistance Gene Pi-ta–Mediated Resistance. Molecular Plant-Microbe Interactions, 2008, 21(4): 396-403

[4] Chun-Lin Huang;Shih-Ying Hwang;Yu-Chung Chiang;Tsan-Piao Lin. Molecular Evolution of the Pi-ta Gene Resistant to Rice Blast in Wild Rice (Oryza rufipogon). Genetics, 2008, 179(3): 1527-1538