Genomic organization and sequence dynamics of the AvrPiz-t locus in Magnaporthe oryzae
Genomic organization and sequence dynamics of the AvrPiz-t locus in Magnaporthe oryzae
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DOI：
10.1631/jzus.b1100338
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发表时间：
2012-06
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影响因子：
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通讯作者：
Ping Li;B. Bai;Hong-Yan Zhang;Heng Zhou;Bo Zhou
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文献类型：
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作者：
Ping Li;B. Bai;Hong-Yan Zhang;Heng Zhou;Bo Zhou
植物利用多层防御机制来对抗不同病原体的入侵。在大多数情况下，R基因介导抗性，依赖于其同源病原体衍生的无毒（Avr）基因的共存。稻瘟病R基因Piz-t以基因对基因的方式对应于稻瘟病菌Avr基因AvrPiz-t。在这项研究中，我们确定并比较了无毒和有毒分离物中AvrPiz-t基因周围的基因组序列，分别命名为AvrPiz-t-ZB 15和avrPiz-t-70-15区域。AvrPiz-t-ZB 15区的序列长度为120 966 bp，而avrPiz-t-70-15区的序列长度为146 292 bp。在AvrPiz-t基因座的预测蛋白质编码区中观察到在avrPiz-t-70-15区域中的极端序列相似性和基因顺序和内容的良好同线性沿着两个预测基因的缺失。然而，频繁存在/不存在和高度动态组织的转座因子（TE）被确定，代表不同菌株之间的AvrPiz-t基因座的主要变化。此外，TE分别占AvrPiz-t-ZB 15和avrPiz-t-70-15区域基因组含量的27.3%和43.2%，表明TE对AvrPiz-t基因座的组织和进化有很大贡献。本研究的结果表明，M。从进化的意义上讲，细菌可以从赋予无毒力的基因中存在的活性TE中受益，并提供快速改变的能力，从而克服宿主R基因。
Plants utilize multiple layers of defense mechanisms to fight against the invasion of diverse pathogens. The R gene mediates resistance, in most cases, dependent on the co-existence of its cognate pathogen-derived avirulence (Avr) gene. The rice blast R gene Piz-t corresponds in gene-for-gene fashion to the Magnaporthe oryzae Avr gene AvrPiz-t. In this study, we determined and compared the genomic sequences surrounding the AvrPiz-t gene in both avirulent and virulent isolates, designating as AvrPiz-t-ZB15 and avrPiz-t-70-15 regions, respectively. The sequence of the AvrPiz-t-ZB15 region is 120 966 bp whereas avrPiz-t-70-15 is 146 292 bp in length. The extreme sequence similarity and good synteny in gene order and content along with the absence of two predicted genes in the avrPiz-t-70-15 region were observed in the predicted protein-coding regions in the AvrPiz-t locus. Nevertheless, frequent presence/absence and highly dynamic organization of transposable elements (TEs) were identified, representing the major variation of the AvrPiz-t locus between different isolates. Moreover, TEs constitute 27.3% and 43.2% of the genomic contents of the AvrPiz-t-ZB15 and avrPiz-t-70-15 regions, respectively, indicating that TEs contribute largely to the organization and evolution of AvrPiz-t locus. The findings of this study suggest that M. oryzae could benefit in an evolutionary sense from the presence of active TEs in genes conferring avirulence and provide an ability to rapidly change and thus to overcome host R genes.