Virus Research 165 (2012) 81–89 Contents lists available at SciVerse ScienceDirect Virus Research journal homepage: www.elsevier.com/locate/virusres The p19 protein of Grapevine Algerian latent virus is a determinant of systemic infection of Chenopodium quinoa Semin Kim a , Won Kyong Cho a , Hyeok-Geun Lee a , Sang-Ho Park a , Seong-Han Sohn b , Kook-Hyung Kim a,c,∗ a Department of Agricultural Biotechnology and Plant Genomics and Breeding Institute, College of Agriculture and Life Sciences, Seoul National University, Seoul 151-921, Republic of Korea b National Academy of Agricultural Science, Rural Development Administration, Suwon 441-707, Republic of Korea c Research Institute for Agriculture and Life Sciences, Seoul National University, Seoul 151-921, Republic of Korea article info Article history: Received 16 November 2011 Received in revised form 31 January 2012 Accepted 31 January 2012 Available online 8 February 2012 Keywords: Tombusvirus Symptom determinant Capsid protein p19 Systemic infection abstract A previous study showed that both Grapevine Algerian latent virus (GALV) and Tomato bushy stunt virus (TBSV) systemically infect Nicotiana benthamiana, but GALV causes systemic infection whereas TBSV causes only local lesions in Chenopodium quinoa (C. quinoa). We recently isolated GALV strain Naju (GALV- N) from Limonium sinense and TBSV strain Sacheon (TBSV-S) from tomato. Both viruses belong to the genus Tombusvirus and have a similar genome organization. To identify determinants of systemic infection of GALV-N in C. quinoa in the current study, we generated infectious clones and capsid protein (CP)- deletion clones for the two viruses and confirmed that CP of GALV-N is required for systemic infection of C. quinoa due to its primary structural role in virus assembly. Through the use of chimeras, we identified a viral factor in addition to CP that contributes to systemic infection by GALV-N. Inactivation of the p19 demonstrated that host-specific activities of p19 are necessary for efficient systemic infection of C. quinoa by GALV-N. Our study is the first report to determine the viral factors required for systemic infection of GALV in C. quinoa. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Systemic infection of plants requires that plant viruses accom- plish genome amplification in the initially infected cells, followed by movement through plasmodesmata to adjacent cells from the initial infected site and long-distance movement in a host through the vascular tissue. For some resistant plants, however, host plants can specifically recognize a viral product to trigger a hypersensitive response (HR) around the initial infection site and restrict viral cell- to-cell movement, which results in a subliminal infection (Sulzinski and Zaitlin, 1982). To overcome resistance response and achieve a successful infection, plant viruses must recognize and utilize fac- tors that are encoded by different host plants. It has been reported that viral factors such as coat protein (CP) and movement protein (MP) and their interactions with host components are involved in the systemic or local infection in diverse plants (Benitez-Alfonso et al., 2010; Scholthof, 2005). ∗ Corresponding author at: Department of Agricultural Biotechnology and Plant Genomics and Breeding Institute and Research Institute for Agriculture and Life Sciences, College of Agriculture and Life Sciences, Seoul National University, Seoul 151-921, Republic of Korea. Tel.: +82 2 880 4677; fax: +82 2 873 2317. E-mail address: kookkim@snu.ac.kr (K.-H. Kim). Tomato bushy stunt virus (TBSV), which belongs to the genus Tombusvirus in the Tombusviridae family, is a positive-sense single- stranded RNA virus (Yamamura and Scholthof, 2005). TBSV has spherical particles about 30 nm in diameter and a genome of about 4.8 kb that encodes five open reading frames (ORFs). ORF1 and ORF 2 are required for viral replication (Scholthof et al., 1995a). ORF3 is associated with expression of capsid protein (CP; p41), whereas ORF4 encodes movement protein (MP; p22), which is involved in viral cell-to-cell movement. ORF5 (p19) is involved in the induction of necrotic symptoms in a host species-dependent fashion, possi- bly by its suppressor activity against RNA-mediated gene silencing (Ahn et al., 2011; Chu et al., 2000; Qu and Morris, 2002; Roth et al., 2004; Thomas et al., 2003). Typically, CP is required for encapsidation of the genome, which prevents RNA degradation, and plays an important role in virus transport (Burgyan et al., 1994). However, TBSV can systemically infect Nicotiana clevelandii (N. clevelandii) and Nicotiana benthami- ana (N. benthamiana) without CP (Scholthof et al., 1993). Some virus proteins have shown to carry silencing suppressor activity and con- tribute to the establishment of systemic infection by inhibiting RNA silencing-mediated degradation of viral RNA (Benitez-Alfonso et al., 2010; Scholthof, 2005). The p19 and CP of the Tombusvirus and the Carmovirus, respectively, have been shown to act as silencing sup- pressors and as pathogenicity factors involved in systemic infection 0168-1702/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.virusres.2012.01.013