Hibiscus chlorotic ringspot virus coat protein is essential for cell-to-cell and long-distance movement but not for viral RNA replication.
Hibiscus chlorotic ringspot virus (HCRSV) is a member of the genus Carmovirus in the family Tombusviridae. In order to study its coat protein (CP) functions on virus replication and movement in kenaf (Hibiscus cannabinus L.), two HCRSV mutants, designated as p2590 (A to G) in which the first start codon ATG was replaced with GTG and p2776 (C to G) in which proline 63 was replaced with alanine, were constructed. In vitro transcripts of p2590 (A to G) were able to replicate to a similar level as wild type without CP expression in kenaf protoplasts. However, its cell-to-cell movement was not detected in the inoculated kenaf cotyledons. Structurally the proline 63 in subunit C acts as a kink for β-annulus formation during virion assembly. Progeny of transcripts derived from p2776 (C to G) was able to move from cell-to-cell in inoculated cotyledons but its long-distance movement was not detected. Virions were not observed in partially purified mutant virus samples isolated from 2776 (C to G) inoculated cotyledons. Removal of the N-terminal 77 amino acids of HCRSV CP by trypsin digestion of purified wild type HCRSV virions resulted in only T = 1 empty virus-like particles. Taken together, HCRSV CP is dispensable for viral RNA replication but essential for cell-to-cell movement, and virion is required for the virus systemic movement. The proline 63 is crucial for HCRSV virion assembly in kenaf plants and the N-terminal 77 amino acids including the β-annulus domain is required in T = 3 assembly in vitro.
Department of Biological Sciences, National University of Singapore, Singapore, Singapore; Key Laboratory of Tropical Crop Biotechnology, Ministry of Agriculture, Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agricultural Science, Hainan, China.
Shengniao
S
Niu
Department of Biological Sciences, National University of Singapore, Singapore, Singapore; Instituto Andaluz de Investigación y Formación Agraria, Pesquera, Alimentaria y de la Producción Ecológica, Almería, Spain.
Francisco M
FM
Gil-Salas
Department of Biological Sciences, National University of Singapore, Singapore, Singapore.
Sunil Kumar
SK
Tewary
Department of Biological Sciences, National University of Singapore, Singapore, Singapore.
Ashwin Kuppusamy
AK
Samales
Department of Molecular Biology, The Scripps Research Institute, California, United States of America.
John
J
Johnson
Department of Biological Sciences, National University of Singapore, Singapore, Singapore.
Kunchithapadam
K
Swaminathan
Department of Biological Sciences, National University of Singapore, Singapore, Singapore; Temasek Life Sciences Laboratory, Singapore, Singapore; National University of Singapore Suzhou Research Institute, Suzhou Industrial Park, Jiangsu, China.
Sek-Man
SM
Wong
D000595:Amino Acid Sequence; D001483:Base Sequence; D036022:Capsid Proteins / Q000235:genetics / Q000378:metabolism*; D019184:Carmovirus / Q000235:genetics / Q000472:pathogenicity*; D002450:Cell Communication; D002465:Cell Movement; D031584:Hibiscus / Q000821:virology*; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics; D012367:RNA, Viral / Q000235:genetics* / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014771:Virion / Q000235:genetics; D014779:Virus Replication
D036022:Capsid Proteins; D012333:RNA, Messenger; D012367:RNA, Viral