Bromoviruses and etc.

Question 1

What is a one-step growth cycle?

Answer 1

• almost all cells are infected at once @ T=0

- virus will start being produced around the same timeline

Question 2

What is a virus spread assay?

Answer 2

• a small percentage of cells are infected @ T=0
• multiple cycles of replication are possible
• potential to observe unique phenomenons

Question 3

What is the Multiplicity of Infection (MOI) ?

Answer 3

• the ratio of infectious units added by # of susceptible cells or (# of infectious units/ number of cells)
• one step use higher MOI
• one step use lower MOI

Question 4

What is a plaque assay (virus spread)?

Answer 4

_ determine the concentration of virus in a sample, measure of infectious virions (plaque-forming units)

• monolayer of cells on top of layer add virus solution, often done for bacteriophage
• for low enough concentrations you get a point of infection

Question 5

What is a Bromovirus?

Answer 5

• Bromus : species of grass
• class IV: linear, +ssRNA genome, segmented genome
• broad host range within plants species
• can be pathogenic or non-pathogenic

Question 6

As with picornaviruses, Bromo virus’s first step of replication is translation for protein, what is one of the first proteins made given the class of the virus is IV?

Answer 6

• RNA-dependent RNA polymerase: one of the first proteins made
• then used to create more negative-strand RNA

Question 7

What is unique about the viruses’ requirements for replication with consideration to it’s genome?

Answer 7

• three different virions with genomic RNA are needed for successful replication

Question 8

Please describe and draw the genome structure for Bromo Vireses

Answer 8

• RNA genoome split into segments
  RNA 1,2,3 are genomic RNA (all needed for replication)
  RNA 4, 4a: Generated in Infected cells
  satellite RNA sometimes present
• Not all RNAs [packaged in a single virions
  1 & 2 packaged separately , 3 & 4 together

Question 9

What is Open reading frame and a reading frame register?

Answer 9

Open reading frame: protein-coding sequence with start and stop codons
reading frame register:

Question 10

Give details on how viral proteins are multifunctional ?

Answer 10

1a: formation of replication factories, methyltransferase (5”capping enzyme), helicase
2a: RNA-dependent RNA polymerase movement in plants
2b: inhibitor of RNA I, movement in plants
3a: movement in viral RNA through plasmodesmata
CP: coat or capsid protein, movement in plants

Question 11

How does Bromovirus enter plants?

Answer 11

• mechanical entry through vectors

- no replication in vector means that vectors are not infected **

Question 12

Now draw out step 2- step 5 of how bromovirus infects cells

Answer 12

really do it!

Question 13

When is a cell considered susceptible ?

Answer 13

• a cell is considered susceptible to virus if the virus can successfully enter the cell

Question 14

When is a cell considered permissive?

Answer 14

• a cell is considered permissive for infection by a particular virus if it supports virus replication to give rise to progeny virus

Question 15

When is pathogen tropism?

Answer 15

• the ability of a pathogen to infect and replicate in a particular tissue, organ species, or cell type. Often depends on the initial interaction of the pathogen with cell surface receptors