类似转录激活因子（transcription activatorlike, tal）基因是水稻白叶枯菌中一类重要的致病相关基因，其编码蛋白属于AvrBs3/pth家族。 tal基因的挖掘和功能分析是揭示白叶枯病菌致病遗传机制的基础。OS198是水稻白叶枯病菌中国菌株6号小种的代表菌株，在供测试的26个水稻品种上毒力较弱。从OS198的基因组中克隆了基因talR26.5。该基因BamHⅠ之间4.281 kb的序列编码26.5个包含34个氨基酸残基的重复单元，在C端具有2个核定位信号（nuclear location signal, NLS）。TALR26.5与菲律宾白叶枯菌株PXO357中的TAL效应蛋白AvrXa73M和日本菌株MAFF311018中的蛋白YP_451895的氨基酸同源性高达99%。 以PXO99A为受体的重组菌PXO99A/talR26.5在水稻IRBB8、IRBB14、IRBB214上毒力比PXO99A显著降低，病斑长度缩短约50%，发病叶片中菌含量也显著下降，但是在包括IRBB7在内的22个品种上的毒力没有改变。半定量PCR检测显示，talR26.5降低了PXO99A对水稻感病基因Os8N3 的诱导表达。在非寄主烟草上接种，talR26.5基因增强了PXO99A在烟草上激发过敏反应的能力。研究结果显示，OS198中的talR26.5基因可能具有毒力和无毒力双重功能。
As the representative strain of Xanthomonas oryzae pv. oryzae (Xoo) China race 6, OS198 displayed low virulence in 26 rice varieties. talR26.5 is a transcription activatorlike (tal) gene cloned from the genomic DNA of OS198. TALR26.5 had 26.5 tandemrepeats of 34 amino acid residues and shared over 99% homology with the TAL effectors AvrXa73M of Philippines strain PXO357 and YP_451895 of Japanese strain MAFF 311018. The repeat domains were identical for the three proteins. The introduction of talR26.5 into PXO99A decreased the virulence and suppressed the bacterial populations in three nearisogenic rice lines IRBB8,IRBB14 and IRBB214 compared with the wild type PXO99A. The transformant strains showed no difference of virulence with PXO99A in 22 other rice varieties including IRBB7. The induced resistance of IRBB8, IRBB14 and IRBB214 against the infection of PXO99A harboring talR26.5 was implemented by the suppression of disease susceptibility gene Os8N3. PXO99A/talR26.5 aroused enhanced hypersensitive response in tobacco leaves compared with PXO99A. The results indicated that the talR26.5 gene of OS198 might have dual functions of virulence and avirulence.
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