Section 5 Final exam Flashcards
Most plant viruses are ______ genomed and there is no normal dsDNA viruses
RNA
Plant virus common characteristics:
1- most plant virus capsids are made of single protien
2- most are icosohedral
3- most have evolved to get their lipid layer from the cells membrane
4- most geminate making “pairs” of two capsids that come together
TMV packaging stages
1- RNA specific structure forms hairpin
2- hairpin goes in and forms into a helical structure as protein (capsid) wraps around the outside
3- RNA is fed through the bottom of the capsid as it assembles toward the 5’ end
TMV will spontaneously assemble in vitro when the RNA and capsid protein are mixed together meaning no ____ are required
cofactors
TMV is a great example of efficient use of limited genome size because it encodes _____ different proteins that are
4 different proteins:
2- versions of the non-structural replication protein
- short version ORF1 is a helices required for efficient replication
- long version ORF2 has RdRp region for RNA synthesis**
** (made in smaller amounts cuz ribosome passes through stop codon after ORF1)
the 4 protiens are:
- 2- versions of the non-structural replication protein
and
- 2 protiens translated from subgenomic RNAs
2- versions of the non-structural replication protein are:
(for making -ve sense RNA)
(don’t go into cell)
- short version ORF1 is a helices required for efficient replication
- long version ORF2 has RdRp region for RNA synthesis**
** (made in smaller amounts cuz ribosome passes through stop codon after ORF1)
- 2 protiens translated from subgenomic RNAs means:
this means translation of ORF1-2 from the genomic RNA
needs to happen after infection, and then the RdRp can make
a –ve sense version of the RNA and the sub-genomic RNAs
can be transcribed from that -ve sense copy by RdRp
individual promoters before those ORFs for their transcription
- 2 protiens translated from subgenomic RNAs are
CP = capsid protein, MP = movement protein
How do viruses move within plants?
(not like animals where they spread within the host as assembled particles)
initial local movements between
neighboring cells (without even making complete virions) by MP
followed later by systemic transmission through the plants’ circulatory system (phloem)
what does MP “movement protein” do?
MP = movement protein: allows infection of neighboring
cells by transporting the viral RNA between cells
What happens if virus that does have ORF for CP gets injected?
can spread to neighbouring cells within
the plant but there will not be a systemic infection
viral RNA moves through plant cell structures called __________ (with the requirement of MP)
plasmodesmata
neither the MP nor viral RNA can pass through
plasmodesmata on their own but when ________, they get through
together
MP binds to the viral ssRNA in
_______ regions to move them between plasmodesmata
non-folded
