Deltasatellite

Satellite virus: infectious only if host cell is co-infected with Begomoviruses

Non-enveloped, rod of filaments of 7 nm in diameter and 1000 to 1200nm long in length. Helical capsid with adsorption proteins on one end.

GENOME

Betasatellites are circular, single-stranded DNAs of approximately 1,350 nucleotides that have no sequence identity to their helper begomoviruses. The betasatellites depend on their helper begomoviruses for replication, and many betasatellites are essential for the induction of typical disease symptoms and viral genome accumulation.

GENE EXPRESSION

Betasatellites encode an approximately 13.5-kDa protein known as beta-C1. Beta-C1 interacts with several host proteins to modulate the plant resistance response and facilitates begomovirus infection and transmission.



REPLICATION

NUCLEAR

  1. Virus penetrates into the host cell.
  2. Uncoating, the viral ssDNA genome penetrates into the nucleus.
  3. The ssDNA is converted into dsDNA with the participation of cellular factors.
  4. bidirectional dsDNA transcription from the IR promoter produces viral mRNAs and translation of viral proteins.
  5. Replication is initiated by cleavage of the(+)strand by REP, and occurs by rolling circle producing ssDNA genomes.
  6. These newly synthesized ssDNA can either
    a) be converted to dsDNA and serve as a template for transcription/replication
    b) be encapsidated by CP and form virions released from the cell by budding
    c) be transported outside the nucleus, to a neighboring cell through plasmodesmata (cell-cell movement) with the help of viral movement proteins.