State Key Laboratory of Rice Biology, Institute of Biotechnology, Zhejiang University, Hangzhou 310029, People's Republic of China.
Plant Physiol. 2011 Nov;157(3):1394-406. doi: 10.1104/pp.111.184648. Epub 2011 Sep 1.
The βC1 protein of tomato yellow leaf curl China β-satellite functions as a pathogenicity determinant. To better understand the molecular basis of βC1 in pathogenicity, a yeast two-hybrid screen of a tomato (Solanum lycopersicum) cDNA library was carried out using βC1 as bait. βC1 interacted with a tomato SUCROSE-NONFERMENTING1-related kinase designated as SlSnRK1. Their interaction was confirmed using a bimolecular fluorescence complementation assay in Nicotiana benthamiana cells. Plants overexpressing SnRK1 were delayed for symptom appearance and contained lower levels of viral and satellite DNA, while plants silenced for SnRK1 expression developed symptoms earlier and accumulated higher levels of viral DNA. In vitro kinase assays showed that βC1 is phosphorylated by SlSnRK1 mainly on serine at position 33 and threonine at position 78. Plants infected with βC1 mutants containing phosphorylation-mimic aspartate residues in place of serine-33 and/or threonine-78 displayed delayed and attenuated symptoms and accumulated lower levels of viral DNA, while plants infected with phosphorylation-negative alanine mutants contained higher levels of viral DNA. These results suggested that the SlSnRK1 protein attenuates geminivirus infection by interacting with and phosphorylating the βC1 protein.
番茄黄曲叶中国β卫星βC1 蛋白作为一个致病性决定因素。为了更好地了解βC1 在致病性中的分子基础，利用βC1 作为诱饵，对番茄（Solanum lycopersicum）cDNA 文库进行了酵母双杂交筛选。βC1 与一种被命名为 SlSnRK1 的番茄蔗糖非发酵 1 相关激酶相互作用。通过在黄花烟细胞中的双分子荧光互补测定实验证实了它们的相互作用。过表达 SnRK1 的植株出现症状的时间延迟，并且含有较低水平的病毒和卫星 DNA，而沉默 SnRK1 表达的植株出现症状的时间更早，并且积累了更高水平的病毒 DNA。体外激酶测定表明，βC1 主要在丝氨酸 33 位和苏氨酸 78 位被 SlSnRK1 磷酸化。感染含有磷酸化模拟天冬氨酸残基代替丝氨酸 33 位和/或苏氨酸 78 位的βC1 突变体的植株表现出延迟和减弱的症状，并且积累的病毒 DNA 水平较低，而感染磷酸化阴性丙氨酸突变体的植株则含有更高水平的病毒 DNA。这些结果表明，SlSnRK1 蛋白通过与βC1 蛋白相互作用和磷酸化来减弱双生病毒的感染。
