Apple chlorotic leaf spot virus 50 kDa movement protein acts as a suppressor of systemic silencing without interfering with local silencing in Nicotiana benthamiana

• DOI: 10.1099/vir.0.82377-0
• Publication Date: 2006-12-15T01:42:25Z
• Authors: Hajime Yaegashi; Tsubasa Takahashi; Masamichi Isogai; Takashi Kobori; Satoshi Ohki; Nobu Yoshikawa
• Keywords: Plant Viral Movement Proteins; Nicotiana; 0301 basic medicine; Luminescent Proteins; Structure-Activity Relationship; Viral Proteins; 0303 health sciences; 03 medical and health sciences; Silencer Elements, Transcriptional; Flexiviridae; 3. Good health

Apple chlorotic leaf spot virus (ACLSV) is the type species of the genus Trichovirus and its single-stranded, plus-sense RNA genome encodes a 216 kDa protein (P216) involved in replication, a 50 kDa movement protein (P50) and a 21 kDa coat protein (CP). In this study, it was investigated whether these proteins might have RNA silencing-suppressor activities by Agrobacterium-mediated transient assay in the green fluorescent protein-expressing Nicotiana benthamiana line 16c. The results indicated that none of these proteins could suppress local silencing in infiltrated leaves. However, systemic silencing in upper leaves induced by both single- and double-stranded RNA could be suppressed by P50, but not by a frame-shift mutant of P50, P216 or CP. Moreover, when P50 was expressed separately from where silencing signals were generated in a leaf, systemic silencing in upper leaves was inhibited. Collectively, our data indicate that P50 acts as a suppressor of systemic silencing without interfering with local silencing, probably by inhibiting the movement of silencing signals.