Plant Virology - Week 14

Question 1

What is TMV?

Why is it important?

Answer 1

Tobacco mosaic virus

First discovered plant virus
First to be discovered to consist of RNA and protein

Question 2

What type of virus (DNA/ RNA etc) is TMV?

Answer 2

single-stranded positive-sense RNA

Made of ridged rods, encodes at least 4 viral proteins

Question 3

How many proteins can 1 RNA make?

Answer 3

Only 1.

1 protein per 1 RNA

Question 4

How does TMV replicate?

Answer 4

Leaky STOP codons (ignores the first STOP codon 105 of the time)

(Look at diagrams)

• 183k and 126k produced
• Replicase moves them to 3’ end
• They then duplicate the genome
• Ribosome then starts on 2/3 START codon to produce 30k and 17.5k

Question 5

How does TMV assemble?

OAS = Origin of assembly

Answer 5

• Where coat proteins first bind to nucleic acid

- The future coat proteins bind to the original coat protein and so on until nucleic acid is covered

Question 6

How does cell to cell movement work for TMV?

Answer 6

Through plant cell pores (Plasmodesmata)

• binds to cell wall then sends viral DNA to cause infection
• Virus eventually reaches phloem, where it is then free to move around plant

Question 7

Role of TMV virus proteins

• 30k
• 17.5k

Answer 7

• Movement protein or transport protein, essential for cell to cell movement
• coat protein, encapsulates the genomic RNA from the virus particles

Question 8

CPMR - transgenic plants safe to eat

coat protein-mediated resistance

Answer 8

BT virus - kills insects not humans

EBF (green gm) amphid alarm chemical, gm into plants to repell amphids

Question 9

How to control plant viruses ?

Answer 9

• Plant virus free seeds/ tubers
• spraying insecticides
• use virus resistant plants
• Cross protection (mild virues inoculated into plants to prevent worse strains)
• Plant transformation (gets into plant nucleus and inputs its DNA for the plant to replicate)

Question 10

TMV replication - look at diagram

Answer 10

TMV replication - look at diagram

in notes too