Análise funcional da via de sinalização antiviral mediada por NIK em tomateiro

• Autor(a) principal: Apfata, Jorge Alberto Condori
• Data de Publicação: 2010
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/4342
• topic: Tomate; NIK (nuclear suttle protein); NIK (NSP-interacting kinase); Tomato; NIK (Suttle nuclear protein); NIK (NSP-interacting kinase); CNPQ::CIENCIAS BIOLOGICAS::BOTANICA::FISIOLOGIA VEGETAL

The begomovirus NSP (nuclear shuttle protein) facilitates the transport of viral DNA from the nucleus to the cytoplasm and cooperates with the movement protein MP to promote the translocation of viral DNA to the adjacent, uninfected cells through plasmodesmata. NSP interacts with members of the LRR-RLK ( leucine-rich repeat receptor like kinase ) family, designated NIKs ( NSP-Interacting Kinase ). Binding of NSP to the activation loop of NIK inhibits kinase activity and hence the viral protein suppresses receptor autophosphorylation and defense responses. Mutagenesis assays in the activation loop of NIK have demonstrated that the threonine 474 residue is phosphorylated in vitro and plays a crucial role in the kinase activity that is required for signaling. Replacement of Thr-474 with aspartate produces the T474 mutant, which exhibits constitutive activation, enhanced substrate phosphorylation activity and less inhibitory effect by NSP binding. The goal of this investigation was to analyse the NIK kinase domain in defense responses against begomovirus in tomato. The NIK mutant T474D cDNA was placed under the control of 35S promoter into a binary vector for plant transformation (35S-AtNIK-T474D). Primary transformants were selected by PCR and the expression of the transgene was confirmed by normal and quantitative RT- PCR in independently transformed lines. NIK and NIK-T474D overexpression in tomato plants affected the overall developmental performance of transgenic lines, which display elongated stems and a root system less developed. These phenotypes were consistent with a cross-communication between the NIK-mediated antiviral signaling and developmental signaling pathways. Infectivity assays were carried out in AtNIK- and AtNIK-T474D-overexpressing lines, with the virus ToYSV-[MG-Bi2]. Overexpression of super active AtNIK-T474D altered the infection rate by ToYSV, and interfered in symptom development. As compared to untransformed plants and NIK- overexpressing 35S-AtNIK1-6 transgenic lines, independent transgenic AtNIK-T474D lines displayed lower infection rate and attenuated symptoms. These results confirmed in planta the essential role for phosphorylation of the Thr-474 residue for NIK function and underlined the possibility for the development of more efficient tolerance strategies against geminiviruses.