A single complementary-sense transcript of a geminiviral DNA beta satellite is determinant of pathogenicity.
Small circular single-stranded DNA satellites, termed DNAbeta, have recently been found associated with some geminivirus infections. The DNA beta associated with Cotton leaf curl virus is responsible for symptom expression of a devastating disease in Pakistan. Mutagenesis of DNA beta revealed that the complementary-sense open reading frame (ORF) betaC1 is required for inducing disease symptoms in Nicotiana tabacum. An ORF present on the virion-sense strand betaV1 appeared to have no role in pathogenesis. Tobacco plants transformed with a betaC1 ORF under the control of the Cauliflower mosaic virus 35S promoter or with a dimeric DNA beta exhibited severe disease-like phenotypes, while plants transformed with a mutated version of betaC1 appeared normal. Northern blot analysis of RNA from the transgenic plants, using strand-specific probes, identified a single complementary-sense transcript. The transcript carries the full betaC1 ORF encoding a 118-amino acid product. It maps to the DNA beta at nucleotide position 186 to 563 and contains a polyadenylation signal 18 nt upstream of the stop codon. A TATA box is located 43 nt upstream of the start codon. Our results indicate that betaC1 protein is responsible for DNA beta-induced disease symptoms.
Saeed
Muhammad
M
Horticulture Unit, CSIRO Plant Industry, RO. Box 350, Glen Osmond, SA 5064, Australia.
Behjatnia
S A Akbar
SA
Mansoor
Shahid
S
Zafar
Yusuf
Y
Hasnain
Shahida
S
Rezaian
M Ali
MA
D000595:Amino Acid Sequence; D001483:Base Sequence; D004276:DNA, Satellite / Q000235:genetics*; D004279:DNA, Viral / Q000235:genetics*; D017791:Geminiviridae / Q000235:genetics / Q000472:pathogenicity*; D003368:Gossypium / Q000821:virology; D008969:Molecular Sequence Data; D009154:Mutation; D016366:Open Reading Frames / Q000502:physiology; D030821:Plants, Genetically Modified; D012333:RNA, Messenger; D012367:RNA, Viral; D014026:Nicotiana / Q000235:genetics
D004276:DNA, Satellite; D004279:DNA, Viral; D012333:RNA, Messenger; D012367:RNA, Viral