Week 7 Module 4

Question 1

Can natural plant viruses have harmful effects?

Answer 1

As with humans, natural plant viruses can have harmful Effects
-viruses can cause diseases in crops and reduce yields

Question 2

Can viruses have benign effects and beneficial?:

Answer 2

-viruses can have relatively benign effects or beneficial from human aesthetics point of view
-e.g. tulip breaking virus (TBV) gives tulips striped or mottled appearance (beauty)
-certain viruses can help plants tolerate drought or high
temperatures
-Benign means neither good nor bad

Question 3

The disadvantages to chemical pesticides?

Answer 3

-Herbicide-resistance weeds have arisen due to chemical pesticide use and selective pressure.

-Insect pests and bacterial pathogens are also issues. Chemical and physical methods being used to control them, not always effective and have associated problems too.

Question 4

Can viruses be used as biopesticides?

Answer 4

-Viruses can be used a biopesticides for agriculturally
important crops.
-in terms of widespread commercial use, it’s emerging field
-part of ‘Integrated Pest Management’ (IPM) plan

Question 5

What is an example of a chemical pesticide that is banned now?

Answer 5

-DET was chemical pesticide that is banned now, issues with chemical pesticides is with low concentration and eventually plants become resistant so have to use higher concentration which is harmful

Question 6

Viruses as biopesticides are used more commonly in___________

Answer 6

South America

Question 7

What is an example of a Biopesticide that can be used?

Answer 7

Baculovirus

Question 8

What are the characteristics of A Baculovirus (used as biopesticide)?

Answer 8

-has dsDNA circular genome
-virions are enveloped and there are types that occur in single
insect infection: budding virus (BV), occluded derived virus (ODV), occlusion body (OB)
-Used to control insects and pests

Question 9

What is a budding virus (BV)?

Answer 9

Has a nucleocapsid coat

Question 10

What is an occluded derived virus (ODV)?

Answer 10

Has another protein matrix coat compared to the budding virus, that surrounds one or a few virions

Question 11

What is an occluded body (OB)?

Answer 11

-Several ODVs that join together and are surrounded by another protein/carbohydrate matrix to from an occlusion body

Question 12

Baculovirus Infection Cycle Step 1 entering Host cell of insects?

Answer 12

-baculovirus infects insects - mainly caterpillars of moths and
butterflies
-alkaline midgut of insect digests OB (occlusion body) and release ODVs (occluded derived virus)
-enzymes from virus degrade midgut membrane and BVs (budding virus) enter epithelial cells

Question 13

Baculovirus Infection Cycle Step 2 viral replication?

Answer 13

-Once budding virus enters epithelial cells viral DNA replicates in nucleus and after initial infection, BVs are made
-BVs infect neighbouring cells to spread infection
-__ insect loses ability to feed after a few days

Question 14

Baculovirus Infection Cycle Step 3 late stage infection?

Answer 14

-at late stage infection, ODVs and OBs are made
-enzymes from ODV break down larval cuticle & liquefy larva
-billions of OBs released and can be spread to other caterpillars horizontal gene transfer (e.g. from virion deposit on leaves)
-may also be transferred vertical transfer (through generations) if OBs remain on eggs

Question 15

Baculovirus uses and challenges?

Answer 15

-used mostly in Latin America
-used to protect soybean, alfalfa, apple, pear, walnut etc. crops
-to create initial infection, infested areas sprayed with concentrated baculovirus solution
-to isolate baculovirus for solution, dead larvae are collected and virions isolated and sprayed elsewhere; Slow and labour intensive

Question 16

Can baculovirus be grown in a bioreactor?

Answer 16

Yes they can be grown in a bioreactor. Trying to grow baculovirus infected insect cells in large scale
in a bioreactor
-challenges are that insect cells are sensitive to shear force and
could be damaged by aeration, agitation etc.
-Controlling bioengineering parameters is critical

Question 17

What is a disadvantage of baculovirus and how can it be improved?

Answer 17

-one limitation of baculovirus is that it takes a few days to
kill caterpillar
-solution, to increase toxicity and speed of action, toxin genes from mites and spiders and scorpions are engineered into virus

Question 18

Other viruses as Biopesticides?

Answer 18

-RNA sequencing of pest larvae being carried out to try and identify sequences of pathogenic viruses they may carry (Insect Control)

-bacteriophages being used to treat bacterial pathogens of important
agriculture crops (Bacterial Control)

-a few cases of viruses being used to control weeds e.g. tropical
soda apple weed which is problem in Florida (Weed Control)

Question 19

Is zoonosis an issue with using viruses from insects as biopesticides?

Answer 19

-Doesn’t appear to be an issue

Question 20

What is a biosensor?

Answer 20

sensors that combine a biological component with a physiochemical component to detect an analyte.

Question 21

Phages as Biosensors

Answer 21

-phage can be used as parts of biosensors to detect foodborne
bacterial pathogens during production and delivery
-Example of Design: Immobilize phage on sensor platform
-if target pathogenic bacteria bind phage, then the mass of
platform increases which leads to measurable signal in readout
that is proportional to amount of pathogen
-(if pathogen absent, nothing will bind the platform)

Question 22

Describe the process of phage being used as a recognition probe for bacterial pathogen detection?

Answer 22

-Ask if bacterial pathogen is in food sample, use biosensor and adhere phage around sensor, put food sample on detector, phage on sensor can infect pathogenic bacteria, phage can stick to it by adherence, there might be bacteria in sample but not a disease causing one, nonpathogenic bacteria can pass phage, can tell by weight— adherence of bacteria to phage adds mass so that’s how you would know if pathogens are there

Question 23

Genetically engineered phage can be used too

Answer 23

• phage can be designed to bind to any bacteria even if bacteria not usually permissive for that phage
  -engineering can increase stickiness of phage to surface
  (e.g. food) that’s being tested
  -several products on the market or being tested

Question 24

Phages that kill Bacterial Pathogens

Answer 24

-in addition to detection, phage might actually be used to kill or reduce load (amount or titer) of pathogenic bacteria.
Example: Listex™ P100
-P100 is a phage that naturally infects L. monocytogenes, bacteria
that causes Listeria
-phage break apart bacterial biofilm and then lyse bacteria
-approved for some uses in Canada

Question 25

Using viral building block (capsomeres of a capsid) as nanomaterial

Answer 25

-Nanoscale size of these ‘building blocks’ or capsomeres, their defined shape and size, ability to self-assemble, and amenability to genetic programming make them attractive to serve as nanomaterials for a host of applications.

-Primary focus of research & development in using viruses for nanomaterials has been on plant-virus derived nanoparticles.

Question 26

What are the Advantages of using Plant Virus Nanoparticles?

Answer 26

-plant viruses generally simple: i) capsids made of one or two proteins ii) Most are naked (unenveloped)
-not pathogenic to humans so medical applications less complicated
-can ‘farm’ nanomaterials to produce them on an industrial scale in environmentally sustainable way
-simple to introduce plant viruses into plant (often by spray)
-fairly easy to purify

Question 27

Assembly and Patterning of Plant-Virus Derived Nanomaterial

Answer 27

Can make 2D surface assembly
-drop solution of PVN and flat solid surface and allow to dry

Can make 3D surface assembly
-layer-by-layer assembly on 3D structure
-Each virus is like a hair on a 3D structure

Question 28

How is further assembly of Plant Virus Nanoparticles done?

Answer 28

-can stabilize PVNs at high temperatures and/or in organic solvents with various treatments (e.g. PEG coating to help with
hydrophobicity)

-can use PVN as ‘ink’ for 2D or 3D printing