BSCTV C2 Attenuates the Degradation of SAMDC1 to Suppress DNA Methylation-Mediated Gene Silencing in Arabidopsis
BSCTV C2 Attenuates the Degradation of SAMDC1 to Suppress DNA Methylation-Mediated Gene Silencing in Arabidopsis
复制标题
BSCTV C2 减弱拟南芥中 SAMDC1 的降解，抑制 DNA 甲基化介导的基因沉默
DOI：
10.1105/tpc.110.081695
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发表时间：
2011-01-01
期刊：
影响因子：
11.6
通讯作者：
Xie, Qi
中科院分区：
文献类型：
--
作者：
Zhang, Zhonghui;Chen, Hao;Xie, Qi
植物病毒是研究微生物-植物相互作用以及宿主活动复杂性的极好工具。本研究主要探讨甜菜严重曲顶病毒（BSCTV）编码的C2在病毒与植物互作中的作用。以BSCTV C2为诱饵，通过酵母双杂交筛选，从拟南芥cDNA文库中鉴定出一个与C2相互作用的蛋白，S-腺苷甲硫氨酸脱羧酶1（SAMDC 1）。这种相互作用通过体外下拉试验和植物中萤火虫荧光素酶互补成像试验来证实。生化分析进一步表明，26 S蛋白酶体抑制剂MG 132可抑制SAMDC 1蛋白的降解，C2可减弱SAMDC 1蛋白的降解。遗传分析表明，SAMDC 1功能的丧失导致对BSCTV感染的易感性降低，并减少病毒DNA积累，类似于BSCTV C2缺陷的效果。亚硫酸氢盐测序分析进一步表明，C2缺陷导致感染植物中病毒基因组DNA甲基化增强。我们还表明，在C2转基因背景下的FWA转基因测定中，C2可以抑制从头甲基化。SAMDC 1的过表达可以模拟C2对绿色荧光蛋白介导的沉默的抑制活性。这些结果表明，C2干扰宿主防御机制的DNA甲基化介导的基因沉默，通过减弱26 S蛋白酶体介导的SAMDC 1的降解。
Plant viruses are excellent tools for studying microbial-plant interactions as well as the complexities of host activities. Our study focuses on the role of C2 encoded by Beet severe curly top virus (BSCTV) in the virus-plant interaction. Using BSCTV C2 as bait in a yeast two-hybrid screen, a C2-interacting protein, S-adenosyl-methionine decarboxylase 1 (SAMDC1), was identified from an Arabidopsis thaliana cDNA library. The interaction was confirmed by an in vitro pull-down assay and a firefly luciferase complemention imaging assay in planta. Biochemical analysis further showed that the degradation of the SAMDC1 protein was inhibited by MG132, a 26S proteasome inhibitor, and that C2 could attenuate the degradation of the SAMDC1 protein. Genetic analysis showed that loss of function of SAMDC1 resulted in reduced susceptibility to BSCTV infection and reduced viral DNA accumulation, similar to the effect of BSCTV C2 deficiency. Bisulfite sequencing analysis further showed that C2 deficiency caused enhanced DNA methylation of the viral genome in infected plants. We also showed that C2 can suppress de novo methylation in the FWA transgenic assay in the C2 transgene background. Overexpression of SAMDC1 can mimic the suppressive activity of C2 against green fluorescent protein-directed silencing. These results suggest that C2 interferes with the host defense mechanism of DNA methylation-mediated gene silencing by attenuating the 26S proteasome-mediated degradation of SAMDC1.