Genetic identification of multiple biological roles associated with the capsid protein of satellite Panicum mosaic virus

• Published in: Molecular plant-microbe interactions Vol. 14; no. 1; pp. 21 - 30
• Main Authors: WENPING QIU, SCHOLTHOF, Karen-Beth G
• Format: Journal Article
• Language: English
• Published: St Paul, MN APS Press 2001; The American Phytopathological Society
• Subjects: Amino Acid Sequence; Base Sequence; Biological and medical sciences; Capsid - genetics; DNA, Complementary - genetics; Fundamental and applied biological sciences. Psychology; Mosaic Viruses - genetics; Mosaic Viruses - pathogenicity; Mutagenesis; Panicum - virology; Panicum miliaceum; Phytopathology. Animal pests. Plant and forest protection; Plant viruses and viroids; RNA, Viral - genetics; Satellite panicum mosaic virus; Satellite Viruses - genetics; Satellite Viruses - pathogenicity; Sequence Deletion; Systematics. Structure, properties and multiplication. Genetics; Tombusviridae - genetics; Tombusviridae - pathogenicity; Virulence - genetics; Monocotyledones; Plant pathogen; Nucleotide sequence; Panicum miliaceum; Satellite virus; Structure function relationship; Cereal crop; Virus; Pathogenicity; Sobemovirus; Structural unit; Virion; Gramineae; Molecular assembly; Angiospermae; Spermatophyta; Capsid; Molecular domain; Panicum mosaic virus; Aminoacid sequence
• ISSN: 0894-0282; 1943-7706
• DOI: 10.1094/MPMI.2001.14.1.21

Satellite panicum mosaic virus (SPMV), an 824-nucleotide, positive-sense, single-stranded RNA virus, depends on Panicum mosaic virus (PMV) for replication and spread in host plants. Compared with PMV infection alone, symptoms are intensified and develop faster on millet plants infected with SPMV and PMV. SPMV encodes a 157 amino acid capsid protein (CP) (17.5 kDa) to encapsidate SPMV RNA and form T = 1 satellite virions. The present study identifies additional biological activities of the SPMV CP, including the induction of severe chlorosis on proso millet plants (Panicum miliaceum cv. Sunup or Red Turghai). Initial deletion mutagenesis experiments mapped the chlorosis-inducing domain to amino acids 50 to 157 on the C-terminal portion of the SPMV CP. More defined analyses revealed that amino acids 124 to 135 comprised a critical domain associated with chlorosis induction and virion formation, whereas the extreme C-terminal residues 148 to 157 were not strictly essential for either role. The results also demonstrated that the absence of SPMV CP tended to stimulate the accumulation of defective RNAs. This suggests that the SPMV CP plays a significant role in maintaining the structural integrity of the full-length satellite virus RNA and harbors multiple functions associated with pathogenesis in SPMV-infected host plants.