Expression of Cucumber mosaic virus suppressor 2b alters FWA methylation and its siRNA accumulation in Arabidopsis thaliana.

Sadia Hamera,Xiaoguang Song,Lei Su,Safee Ullah Chaudhary,Muhammad Tariq,Iram Murtaza,Xiaoying Chen,Rongxiang Fang,Youngsheng Yan

doi:10.1242/bio.017244

Abstract

ABSTRACTThe Cucumber mosaic virus (CMV) suppressor 2b co-localizes with AGO4 in cytoplasmic and nuclear fractions of Arabidopsis thaliana. Biochemical fractionation of A. thaliana cellular extracts revealed that 2b and AGO4 coexist in multiple size exclusions. 2b transgenic A. thaliana exhibited an enhanced accumulation of 24nt siRNAs from flowering wageningen (FWA) and other heterochromatic loci. These plants also exhibited hypo-methylation of an endogenous- as well as transgene-FWA promoter at non-CG sites. In corroboration, both transgenic 2b and CMV infection affected the regulation of transposons which mimics the ago4 phenotype. In conclusion, 2b perturbs plant defense by interfering with AGO4-regulated transcriptional gene silencing.

Highlights

RNA silencing is a conserved nucleotide sequence-specific gene inactivation mechanism which controls a wide range of functions including gene regulation, heterochromatin formation (Matzke et al, 2004) and antiviral resistance (Ding and Voinnet, 2007)
In this study we found that AGO4 accumulation is not effected by 2b and Cucumber mosaic virus (CMV) infection in A. thaliana plants; overlapping expression patterns in cellular fractions and size exclusion chromatography (SEC) shows the ability of 2b to interact with AGO4
CMV infection and transgenic expression of 2b induces phenotypic anomalies in A. thaliana CMV-induced variable symptom severity in host plants is correlated with the virus strains

Summary

Introduction

RNA silencing is a conserved nucleotide sequence-specific gene inactivation mechanism which controls a wide range of functions including gene regulation, heterochromatin formation (Matzke et al, 2004) and antiviral resistance (Ding and Voinnet, 2007). It invariably relies on a set of core elements that triggers the processing of doublestranded RNA into small RNA (sRNA) duplexes of 21-24nt in length. These sRNAs organize the complex mechanism of gene regulation at transcriptional, post-transcriptional and translational levels (Hammond, 2005). RDR2 converts target mRNA into dsRNA by the coordinated action of POLIV, and the dsRNA

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Conclusion