摘要
The rice disease resistance （R） gene Xa3/Xa26 （having also been named Xa3 and Xa26） against Xanthomonas oryzae pv. oryzae （Xoo）, which causes bacterial blight disease, belongs to a multiple gene family clustered in chromosome 11 and is from an AA genome rice cultivar （Oryza sativa L.）. This family encodes leucine-rich repeat （LRR） receptor kinase- type proteins, Here, we show that the orthologs （alleles） of Xa3/Xa26, Xa3/Xa26-2, and Xa3/Xa26-3, from wild Oryza spe- cies O. officinalis （CC genome） and O. minuta （BBCC genome）, respectively, were also R genes against Xoo. Xa3/Xa26-2 and Xa3/Xa26-3 conferred resistance to 16 of the 18 Xoo strains examined. Comparative sequence analysis of the Xa3/Xa26 families in the two wild Oryza species showed that Xa3/Xa26-3 appeared to have originated from the CC genome of O. minuta. The predicted proteins encoded by Xa3/Xa26, Xa3/Xa26-2, and Xa3/Xa26-3 share 91-99% sequence identity and 94-99% sequence similarity. Transgenic plants carrying a single copy of Xa3/Xa26, Xa3/Xa26-2, or Xa3PXa26-3, in the same genetic background, showed a similar resistance spectrum to a set of Xoo strains, although plants carrying Xa3/Xa26-2 or Xa3/Xa26-3 showed lower resistance levels than the plants carrying Xa3/Xa26. These results suggest that the Xa3/Xa26 locus predates the speciation of A and C genome, which is approximately 7.5 million years ago. Thus, the resistance spec- ificity of this locus has been conserved for a long time.
The rice disease resistance （R） gene Xa3/Xa26 （having also been named Xa3 and Xa26） against Xanthomonas oryzae pv. oryzae （Xoo）, which causes bacterial blight disease, belongs to a multiple gene family clustered in chromosome 11 and is from an AA genome rice cultivar （Oryza sativa L.）. This family encodes leucine-rich repeat （LRR） receptor kinase- type proteins, Here, we show that the orthologs （alleles） of Xa3/Xa26, Xa3/Xa26-2, and Xa3/Xa26-3, from wild Oryza spe- cies O. officinalis （CC genome） and O. minuta （BBCC genome）, respectively, were also R genes against Xoo. Xa3/Xa26-2 and Xa3/Xa26-3 conferred resistance to 16 of the 18 Xoo strains examined. Comparative sequence analysis of the Xa3/Xa26 families in the two wild Oryza species showed that Xa3/Xa26-3 appeared to have originated from the CC genome of O. minuta. The predicted proteins encoded by Xa3/Xa26, Xa3/Xa26-2, and Xa3/Xa26-3 share 91-99% sequence identity and 94-99% sequence similarity. Transgenic plants carrying a single copy of Xa3/Xa26, Xa3/Xa26-2, or Xa3PXa26-3, in the same genetic background, showed a similar resistance spectrum to a set of Xoo strains, although plants carrying Xa3/Xa26-2 or Xa3/Xa26-3 showed lower resistance levels than the plants carrying Xa3/Xa26. These results suggest that the Xa3/Xa26 locus predates the speciation of A and C genome, which is approximately 7.5 million years ago. Thus, the resistance spec- ificity of this locus has been conserved for a long time.
基金
This work was supported by grants from the National Program on the Development of Basic Research in China，the National Natural Science Foundation of China
