Abiotic Stress

Question 1

Name 5 abiotic stresses

Answer 1

Light, water, salinity, heavy metals, radiation

Question 2

How much of crop yield is lost to abiotic stress?

Answer 2

50%

Question 3

What percent of crops are currently being used to feed animals?

Answer 3

36%

Question 4

What yield increase is required per annum to meet our demands?

Answer 4

2.4%

Question 5

How will an annual plant react to stress (e.g. drought)

Answer 5

Transition to reproductive mode - more flowers and seed production

Question 6

Name for acclimation in horticulture

Answer 6

Hardening

Question 7

What is the role of genomics in plant science?

Answer 7

Allows scientists to look for markers and possible targets for manipulation

Question 8

What % of worlds water is available for plants to use?

Answer 8

<1%

Question 9

Money lost in US due to drought?

Answer 9

$130 million

Question 10

What perecentage of cultivatable land is affected by salinity?

Answer 10

5%

Question 11

What % of wheat belt is affected in Oz?
How much do wheat exports total?
How much do crop losses cost per year from salt stress?

Answer 11

70-80%
$4 Billion
>$500 million

Question 12

What is meant by the dual function of Reactive Oxygen Species (free radicals)?

Answer 12

They act as a positive activator in signal pathways but have a negative impact on growth

Question 13

What are the most common forms of ROS?

Answer 13

Superoxide anion, peroxyls, hydroxyls

Question 14

Most common outcomes of ROS

Answer 14

Lipid peroxidation, DNA/RNA damage, protein oxidation

Question 15

What are the 3 stages of increased oxidative modification of a protein?

Answer 15

Low oxidation protein can hold shape, moderate protein will unravel and become linear, high oxidation now hydrophobic protein will agregate with other proteins forming large inhibitory mess.

Question 16

What 3 conditions can lead to osmotic stress?

Answer 16

Salt, drought, cold

Question 17

Where are excess ions stored to avoid disruption of metabolic processes?

Answer 17

In the vacuole

Question 18

What are the effects of drought on root phenotype?

Answer 18

Roots grow longer and less branched

Question 19

What sites particularly produce ROS?

Answer 19

Sites of electron transport especially around the plastid/mitochondria since plants cannot regulate the transport

Question 20

What is the role of a molceular chaperone?

Answer 20

Acts as a detoxifying method by assisting the folding of proteins

Question 21

How does HSP60 assist in protein folding?

Answer 21

Barrel shaped structure sucks in amino acid chain into hydrophobic space and shoots out refolded protein.

Question 22

How does HSP33, HSP31 and smallHSPs assist under stress?

Answer 22

Attempt to pull apart large aggregates of protein

Question 23

How does HSP70 and 90 assist in protein folding?

Answer 23

Work alongside large HSP101 to dissaggregate large protein and reassemble protein (90 is magnet shaped) but this takes ATP.

Question 24

What does mannitol do in an experiment?

Answer 24

Mimicks a drought environment by making water move out of the roots

Question 25

How can we combat the drought effects of mannitol using genetic engineering?

Answer 25

Constant expression of HSP90

Question 26

What is measured in the mannitol experiment to show the effect of HSP?

Answer 26

Chlorophyll levels

Question 27

How does the technology in DroughtGuard improve dorught tolerance?

Answer 27

Processing bodies (degredation of mRNA) and stress granules (protect and stabilize mRNA under stress) are produced in the cytosol to deal with aggregating mRNA.

Question 28

What does PolyacrylAmide Gel Electrophoresis help you determine?

Answer 28

Seperate proteins by size and isoelectric point

Question 29

Where were binding proteins for mRNA known as cold shock proteins (used in DroughtGuard) first isolated from?

Answer 29

E-Coli in the 1980s

Question 30

Describe the bacterial CSP-mRNA surveillance system

Answer 30

Under cold conditions, linear mRNA switches to structured mRNA which cannot be translated. Under these conditions, cspA is also produced which binds to mRNA, teasing apart the tight structure. Anything that does not get well linearised is degraded.

Question 31

What was the step between CSP being expressed in bacteria to maize?

Answer 31

A model plant - Arapidopsis

Question 32

What species was the specific CSP-B isolated from to be used in maize in Drought-Gard and why?

Answer 32

Bacillus Subtilus, it is already commonly used in fermented food so can be tested for safety.

Question 33

How can movement of solutes into the vacuole help stress defence in plants?

Answer 33

In stress, the osmotic value outside of plants tends to be very low (with many solutes) causing water to move out. By moving solutes out of cytosol and into vacuole, it means water moves towards vacuole and water will continue to move into cell.

Question 34

Which solute naturally builds up in cotton that can aid with stress?

Answer 34

Glycine Betaine

Question 35

Describe the biosynthetic pathway that leads to glycine betaine IN PLANTS

Answer 35

Choline monooxygenase creates an aldehyde that then is converted to glycine betaine by a dehydrogenase enzyme.

Question 36

Describe the biosynthetic pathway of GS IN E.COLI

Answer 36

Choline monooxygenase is subbed out for choline dehydrogenase (an enzyme targetted by genetic engineering)

Question 37

Is the expression of choline dehydrogenase enzyme succesful in increasing plant yield?

Answer 37

Yes but no technology is currently on the market.

Question 38

How does active transport in the roots limit salt stress in a plant?

Answer 38

Actively transport Na+ out of xylem and into root parenchhyma cells to reduce concentrations of Na+ in the leaves.