Involvement of C4 protein of beet severe curly top virus (family Geminiviridae) in virus movement.
BACKGROUND
Beet severe curly top virus (BSCTV) is a leafhopper transmitted geminivirus with a monopartite genome. C4 proteins encoded by geminivirus play an important role in virus/plant interaction.


RESULTS
To understand the function of C4 encoded by BSCTV, two BSCTV mutants were constructed by introducing termination codons in ORF C4 without affecting the amino acids encoded by overlapping ORF Rep. BSCTV mutants containing disrupted ORF C4 retained the ability to replicate in Arabidopsis protoplasts and in the agro-inoculated leaf discs of N. benthamiana, suggesting C4 is not required for virus DNA replication. However, both mutants did not accumulate viral DNA in newly emerged leaves of inoculated N. benthamiana and Arabidopsis, and the inoculated plants were asymptomatic. We also showed that C4 expression in plant could help C4 deficient BSCTV mutants to move systemically. C4 was localized in the cytosol and the nucleus in both Arabidopsis protoplasts and N. benthamiana leaves and the protein appeared to bind viral DNA and ds/ssDNA nonspecifically, displaying novel DNA binding properties.


CONCLUSIONS
Our results suggest that C4 protein in BSCTV is involved in symptom production and may facilitate virus movement instead of virus replication.
Teng
Kunling
K
State Key Laboratory of Plant Genomics and National Center for Plant Gene Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.
Chen
Hao
H
Lai
Jianbin
J
Zhang
Zhonghui
Z
Fang
Yuanyuan
Y
Xia
Ran
R
Zhou
Xueping
X
Guo
Huishan
H
Xie
Qi
Q
D017360:Arabidopsis / Q000821:virology; D004261:DNA Replication; D004279:DNA, Viral / Q000096:biosynthesis / Q000235:genetics; D017791:Geminiviridae / Q000235:genetics / Q000502:physiology*; D009154:Mutation; D014026:Nicotiana / Q000821:virology; D014764:Viral Proteins / Q000235:genetics / Q000502:physiology*
D004279:DNA, Viral; D014764:Viral Proteins