Tomato geminivirus encoded RNAi suppressor protein, AC4 interacts with host AGO4 and precludes viral DNA methylation

44 p.-4 fig.-1 tab.Plant RNA silencing systems are organized as a network, regulating plant developmental pathways and restraining invading viruses, by sharing cellular components with overlapping functions. Host regulatory networks operate either at the transcriptional level via RNA-directed DNA methylation, or at the post-transcriptional stage interfering with mRNA to restrict viral infection. However, viral-derived proteins, including suppressors of RNA silencing, favour virus establishment, and also affect plant developmental processes. In this investigation, we report that Tomato leaf curl New Delhi virus-derived AC4 protein suppresses RNA silencing activity and mutational analysis of AC4 showed that Asn-50 in the SKNT-51 motif, in the C-terminal region, is a critical determinant of its RNA silencing suppressor activity. AC4 showed interaction with host AGO4 but not with AGO1, aggregated around the nucleus and influenced cytosine methylation of the viral genome. The possible molecular mechanism by which AC4 interferes in the RNA silencing network, helps virus establishment, and affects plant development is discussed.This work was supported by ICAR-IARI, New Delhi. We are also thankful to Council of Scientific and Industrial Research (CSIR) and Department of Biotechnology, New Delhi for providing fellowship to GK, and VG. The Next Generation BioGreen21 Program (Grant no. PJ011309032017) of the Rural Development Administration, and Grant no. NRF-2016R1D1A1B03930764 from the Korean National Research Foundation, both from the Republic of Korea to P. P. are also acknowledged.Peer reviewe