Roeschlin Roxana Andrea, Uviedo Facundo, García Lucila, Molina María Celeste, Favaro María Alejandra, Chiesa María Amalia, Tasselli Sabrina, Franco-Zorrilla José Manuel, Forment Javier, Gadea José, Marano María Rosa
Instituto de Biología Molecular y Celular de Rosario (IBR)-Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET), Ocampo y Esmeralda S/N, S2002LRK, Rosario, Argentina.
Área Virología, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario (UNR), Suipacha 590, S2002LRK, Rosario, Argentina.
Mol Plant Pathol. 2019 Oct;20(10):1394-1407. doi: 10.1111/mpp.12844. Epub 2019 Jul 5.
Transcription activator-like effectors (TALEs) are important effectors of Xanthomonas spp. that manipulate the transcriptome of the host plant, conferring susceptibility or resistance to bacterial infection. Xanthomonas citri ssp. citri variant A (X. citri A ) triggers a host-specific hypersensitive response (HR) that suppresses citrus canker development. However, the bacterial effector that elicits this process is unknown. In this study, we show that a 7.5-repeat TALE is responsible for triggering the HR. PthA4 was identified within the pthA repertoire of X. citri A followed by assay of the effects on different hosts. The mode of action of PthA4 was characterized using protein-binding microarrays and testing the effects of deletion of the nuclear localization signals and activation domain on plant responses. PthA4 is able to bind DNA and activate transcription in an effector binding element-dependent manner. Moreover, HR requires PthA4 nuclear localization, suggesting the activation of executor resistance (R) genes in host and non-host plants. This is the first case where a TALE of unusually short length performs a biological function by means of its repeat domain, indicating that the action of these effectors to reprogramme the host transcriptome following nuclear localization is not limited to 'classical' TALEs.
转录激活样效应因子（TALEs）是黄单胞菌属的重要效应因子，可操纵宿主植物的转录组，赋予宿主对细菌感染的易感性或抗性。柑橘黄龙病菌变种A（X. citri A）引发宿主特异性过敏反应（HR），抑制柑橘溃疡病的发展。然而，引发这一过程的细菌效应因子尚不清楚。在本研究中，我们表明一个7.5个重复单元的TALE负责触发HR。在X. citri A的pthA基因库中鉴定出PthA4，随后分析其对不同宿主的影响。使用蛋白质结合微阵列并测试核定位信号和激活域缺失对植物反应的影响，对PthA4的作用模式进行了表征。PthA4能够以效应子结合元件依赖的方式结合DNA并激活转录。此外，HR需要PthA4的核定位，这表明宿主植物和非宿主植物中的执行抗性（R）基因被激活。这是首次发现一个长度异常短的TALE通过其重复结构域发挥生物学功能，表明这些效应因子在核定位后对宿主转录组进行重编程的作用不限于“经典”TALEs。
