Covariation in the capsid protein of hibiscus chlorotic ringspot virus induced by serial passaging in a host that restricts movement leads to avirulence in its systemic host.
Hibiscus chlorotic ringspot virus (HCRSV) from naturally infected Hibiscus rosa-sinensis L. loses virulence in its experimental systemic host Hibiscus cannabinus L. (kenaf) after serial passages in a local lesion host Chenopodium quinoa. Here we report the genetic changes responsible for the loss of virulence at the molecular level. A remarkable covariation of eight site-specific amino acids was found in the HCRSV capsid protein (CP) after serial passages in C. quinoa: Val(49)-->Ile, Ile(95)-->Val, Lys(270)-->Arg, Gly(272)-->Asp, Tyr(274)-->His, Ala(311)-->Asp, Asp(334)-->Ala, and Ala(335)-->Thr. Covariation of at least three of the eight amino acids, Val(49), Ile(95), and Lys(270), caused the virus to become avirulent in kenaf. Interestingly, the nature of the covariation was consistent and reproducible at each serial passage. These data indicate that the nonsynonymous substitutions of amino acids in the HCRSV CP after serial passages in C. quinoa are not likely to be random events but may be due to host-associated positive selection or accelerated genetic drift. The observed interdependence among the three amino acids leading to avirulence in kenaf may have implications for structural or functional relationships in this virus-host interaction.
Liang
Xiao-Zhen
XZ
Department of Biological Sciences, The National University of Singapore, Singapore 117543, Republic of Singapore.
Lee
Bernett T K
BT
Wong
Sek-Man
SM
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001483:Base Sequence; D036022:Capsid Proteins / Q000235:genetics*; D019184:Carmovirus / Q000235:genetics* / Q000472:pathogenicity* / Q000502:physiology; D027465:Chenopodium quinoa / Q000821:virology; D004279:DNA, Viral / Q000235:genetics; D005814:Genes, Viral; D014644:Genetic Variation; D031584:Hibiscus / Q000821:virology; D017354:Point Mutation; D012692:Serial Passage; D014774:Virulence / Q000235:genetics; D014779:Virus Replication
D036022:Capsid Proteins; D004279:DNA, Viral