Plant Sciences Flashcards
(115 cards)
1
Q
What have plants done for us?
A
- food
- buildings (wood)
- materials
- clothes
- paper
- landscapes
AND MANY MORE
2
Q
Global challenges
A
- food security and nutrition
- water security
- energy security
- medicine and pharmacology
- environmental sustainability
- wealth distribution
3
Q
Norman Borlaug
A
Norman Borlaug won the Nobel Peace Prize 1970 for developing a semi-dwarf, high yield variety of wheat Beforehand, the wheat plants were too tall and so very fragile and subject to damage. He developed a shorter, stronger variety and so is referred to as the father of “Green revolution”
4
Q
Factors challenging food security
A
Land and Soils
- 25% of the planet’s land is highly degraded
Climate change
- temperatures are exceeding survival thresholds of crop, tree and fish species
Energy
- modern food systems are heavily dependent on fossil fuels
- 85% of total primary energy is fossil fuel bases
5
Q
World population and food security
A
- World population will be ~9billion by 2050
- food production will need to double
6
Q
GM crops
A
genetically modified
7
Q
Potential benefits of GM crops
A
- overcome linkage drag, “clean” gene movement
- introduce novel abilities
- more rapid breeding cycles
- increased food production
- improved human nutrition
- wealth distribution
- open up marginal land
- increase land and water use efficiency
- reduced environmental impact (CO2 and NO)
- reduced fertiliser use
- reduced herbicide, pesticide, fungicide, bactericide use
- reduced soil damage
8
Q
Potential problems of GM crops
A
- commercial interests
- loss of ecological diversity
- gene transfer to wild relatives
9
Q
Are GM crops unnatural?
A
You can also get natural genetically modified crops due to horizontal gene transfer e.g. sweet potatoes are genetically modified by agrobacterium species and are the 7th most important crop.
10
Q
GM crop summary
A
- increases yield (22%)
- decreases pesticide quantity (-40%)
- decreases pesticide cost (39%)
- increases total production cost (3%)
- increases farmer profit (68%)
11
Q
Solanum Tuberosum (GM crop)
A
- 3rd most important crop worldwide
- uses 2/3 water of rice for same calorific yield
- 25% of global crop lost to disease each year (enough to feed UK for 15 years!)
12
Q
Phytopthora Infestans (GM crop)
A
- GM potato
- causative agent of the irish potato famine
- new strain “blue13” is able to overcome all current blight resistances
Challenges:
- more resistant varieties of potato
- new, less harmful control measures
In the wild, disease is the exception and resistance is the norm, so why do our potatoes get infected?
13
Q
GM potato - traditional breeding vs GM
A
Traditional: ~25 year per gene moved
GM: ~24 months, independent of gene numbers
- transfer multiple resistance genes simultaneously
- multiple resistant potato
- yield and character maintained
14
Q
Nitrogen-fixing cereals
A
- N2 fertiliser use accounts for 5% of global energy (and is increasing)
- N2 fertiliser allows for ~3-4x increased crop yield
- expensive
- 2/3 of applied N2 is lost to environment
15
Q
Crops for the future
A
- snorkel rice (flood resistant)
- sub rice (submergence resistant)
- C4 rice
- golden rice - increased vitamin A content
16
Q
Folk medicine
A
- morphine, codeine - analgaesic
- digitalin - heart arrythmia
- quinine, artemisin - malaria
- colchicine - gout
- tansy - embalming, roundworm, threadworm
- salicylic acid - warts and other skin conditions
- laudanum - pain killer and cough represent
- eating daffodils - vomiting, whooping cough, cold and asthma
17
Q
Drug discovery
A
- 55% of drugs owe their origins to plants
- 25% of all drug are still made directly from plants
- 60% of anti-cancer drugs are of plant origin
18
Q
MDR malaria
A
- artemisinin
- artemesia
- green small leaved plant
19
Q
lung/breast/ovarian cancer
A
- taxol
- yew
- pine-like leaves with berries
20
Q
leukaemia
A
- vincristine
- madagascan periwinkle
- pink/purple flowering plant with small rounded leaves
21
Q
asthma
A
- ephedrine
- ephedra
- no leaves some small buds
22
Q
pain, fever, inflammation
A
- asparin
- willow
23
Q
chronic and acute pain
A
- morphine
- opium poppy
24
Q
alzheimers
A
- galantamine
- snowdrop
25
bradychardia
- atropine
- deadly nightshade
- quite large pointed leaves with purple flowers
26
heart arrhythmia
- digoxin
- foxglove
- purple/pink cone like flowers
27
Metabolic diversity of plants
- high
- naturally produce anti-microbial and anti-herbivory compounds
- ~20% of all global flora re used in folk remedies
- <1% of known plant species have been assessed for bioactive compounds
28
Why start with natural products? (drug discovery)
- pre-screended in folk medicine (ethnopharmacology)
- active in the cell
- higher chance of biological activity
- combinatorial effecs
- community benefit
29
Vaccines
- 4-5 weeks after outbreak
- HIV, viral and bacterial diarrhoea, anthrax, rabies, diphtheria, malaria, alzheimer's etc.
- can be edible
- store as seed for when needed
30
Plants as medical bioreactors
- many post-translational modifications are maintained, can also be "humanised"
- maintain stereochemistry
- cheap to grow
- store as seed for when needed
- edibility
- interleukin, interferon, factor VIII, hGH
31
Energy security
- e.g. waste miscanthus is used as straw on farms
- algae + CO2 = oil
- can use "dirty" water and waste CO2
- capture waste NPK from agricultural run off
- remove heavy metal pollutants
- algal residue contains many useful compounds
32
Plants as chemical bioreactors
- stereochemistry can be maintained
- complex syntheses can be achieved through gene stacking
- perform complex organic chemistry at room temperature in water
- cheap to grow
- store as seed for when needed
- main chassis for synthetic biology
33
Are plants conscious?
- perceive light from UV to infra-red
- detect and differentiate touch
- smell/taste more than any animal
- conduct electrical impulses and have glutamate receptors
- long and short term memory
- they are more complex at the genetic, biochemical and environmental level than any animal
34
What is the world's most important food crop?
- maize (corn)
- USA is biggest producer
- staple food for the majority of the sub-saharan africa
- being used more and more for ethanol
- dometicated about 10,000 mya in southern mexico
- over 800 million metric tonnes produced
35
What is the second most important food crop?
- rice
- over 700 million metric tonnes produced
- main producer is China
- may be even more important than corn as a food crop as corn is used for other purposes besides consumption
- thirstiest crop (need at least 2,000 litres of water per kg)
- domesticated 11,000-12,000 mya in China
36
what is polished rice deficient in?
provitamin A
37
Which have been the focus crops of the Green revolution?
rice and wheat
38
Why is there pressure on food security?
the yield increases have lagged behind human population growth in areas where rice is a dominant crop for human consumption
39
Rice genome sequencing
- completed in Jan 2001
| - could lead to breakthroughs for higher yields
40
Rice GM crops
- golden rice
| - a cultivar that has been genetically modified to produce higher levels of vitamin A
41
What is the third most important crop?
- wheat
- ~700 million metric tonnes produced
- major producer is China
- covers more of earth than any other crop
- resilient, grows in dry and cold climates where rice and maize cannot
- leading source of vegetable protein for humans
- domesticated ~10,000 mya in the fertile crescent
42
What percentage of the world's food energy intake do rice, maize and wheat provide?
60%
43
How many edible plants are there
Over 50,000
44
What is the fourth most important food crop?
- potatoes
- over 300 million metric tonnes produced
- China is major producer
- not a cereal like the others, the number one non-grain food product
- grows best in temperate climates
- originally grown in the Andes
- Spanish introduced to Europe in 16th century
- really high in nutrients
45
How much land is used for agriculture?
- half
- has a huge impact on the ecosystem and world function
- ~1/4th of that is crops
- vast majority = cereals (main three)
46
Where do we get the vast majority of our calories?
cereals
47
Double fertilisation
- sperm meets egg in ovule (fertilisation)
- another sperm fertilises the polar nuclei
- the endosperm is huge in the cereal
- the endosperm is a food source for the embryo
48
Why were cereal plants domesticated
- they taste good
- initially has lots of nutrients
- can be stored
- basis for civilisation
- allows us to get on with education, building, developing etc.
49
Crop domestication
- wild cereal
- cultivation/domestication
- selective breeding (landraces)
- modern cereal
50
Domestication of cereals for increase in grain yield
- first step was loss of shattering
- loss of vernalisation requirement
- increased seed number
- reduced seed shattering
- reduced height
- reduced dormancy
51
Tough rachis mutation
- loss of seed dispersal (shattering)
- results in grain remaining attached to the mature ear
- often considered the most important domestication trait as it makes propagation of the plant dependent on human intervention
- higher yields
- can delay harvesting until grains have matured
52
What does the loss of grain dispersal aid?
- e.g. hairs, hooks and awns
- these facilitate wind and animal dispersive processes
- natural selection for grain dispersal aids is lost once the ear becomes nonadhescent and partly from human selection for grain morphologies that simplify postharvest crop cleaning
53
Increase in grain size
- can arise by direct selection or via tillage
- tillage: larger grain surviving deeper burial
- grain size is often used as an indication of human intervention in plant reproduction
54
loss of sensitivity to environmental cues for germination and flowering
- the grains of most crops germinate too soon after planting
- the wild versions often germinate only in response to environmental cues such as day length and temperature
- this is thought to be selected by cultivators using grain from the previous harvest to sow the succeeding crop, as grain that germinates slowly will make a decreasing contribution the the harvesting crop
55
Synchronous tillering and ripening
- selected by cultivation practices especially as these develop into a continuous annual cycle
56
Compact growth habit
- selected by harvesting methods that preferentially sample plants of similar size and shape
57
Enhanced culinary chemistry
- e.g. improved breadmaking quality of wheat and changes to the sugar-starch balance in maize
58
Examples of altered development of non-cereals
- kale (leaves)
- broccoli (flower buds and stem)
- cabbage (terminal leaf bud)
- cauliflower (flower buds)
- brussel sprouts (lateral leaf buds)
- kohlrabi (stem)
59
Rice gene qSH1
- controls abscission zone formation at base of rice flower
- single nucleotide polymorphism (SNP) in 5' regulatory region of a single transcription factor was responsible for nonshattering rice
60
Maize TGA and TB1
- both encode transcription factors
- TGA promotes development of tough case around kernal
- TB1 suppresses branching to promote single stalk
61
The population bomb
- Since 1900, the population has increased from ~1.6 billion to ~8 billion
- how do we feed all these people?
62
The green revolution
- one of the most significant accomplishments of 20th century science was the development of lodging-resistant, high-yielding semi-dwarf grain varieties
63
Green revolution varieties of wheat had ...
Gibberellin (GA) hormone biosynthesis
64
GA signalling pathway
*WAITING ON DIAGRAM*
65
Submergence tolerance problem
- more than 16 million ha of land used to grow rice in lowland ares and deep-water areas are unfavourably affected by flooding
- the estimated annual economic loss of this is more than US$ 600 million
- climate change will increase flash flooding where most of the world's rice is grown
- for deepwater rice, water stands for long periods. If the plant does not elongate sufficiently, it will drown, set poor grain and/or die
66
Submergence tolerance solution
- for deepwater floods, rice needs to escape the water and float
- SK = snorkel proteins
- most lowland rice will show stem elongation when completely submerged to try and escape out, the rice uses up its carbohydrates reserves and may die
- some tolerant landraces show quiescence, enter a dormant, quiescent state rather than try and grow out of the water (conserve energy and survive)
67
What is quiescence controlled by?
the SUB1A gene that encodes an ethylene responsive transcription factor (ERF)
68
Submergence tolerece signalling pathway
- submergence
- ethylene (SK1/SK2 also induced by ethylene but act differently from SUB1A and promote GA-induced stem elongation)
- ABA/ SLR1 +SLRL1 (dellas)
- GA responses
- CHO consumption
- elongation growth
69
Why couldn't we live without plants?
- produce most of the oxygen we breathe
- produce most of the chemically stored energy we consume as food and burn for fuel
- produce an amazing assortment of useful chemicals
70
Globally, how many people per year are chronically hungry?
- more than one billion
- more than the total population of the USA, Canada and the EU
- although a lot of people have a lot to eat they are not very nutritious
71
How many people per year are chronically anemic due to iron deficiency?
- more than 2 billion
| - about the total population of the USA, Canada, the EU and China
72
Plant scientists can contribute to the allevation of hunger by developing plants that...
- are drought or stress tolerant
- require less fertiliser or water
- are resistant to pathogens
- are more nutritious
73
Plant-microbe associations (positives)
- essential for C and N recycling
- important for plant growth (water and minerals)
- important to strengthen plant health
74
Plant - microbe associations (negatives)
- detrimental to plant health
- threat to crop production for human food and energy
- threat to natural ecosystems
75
Plant mutualism
- enhances reproduction and nutrient uptake
- plants cooperating with other organisms
- e.g. pollination, seed dispersal, nitrogen fixing endosymbiosis, mycorrhizal symbiosis
76
Mutualistic associations with root symbionts
- with soil organisms
| - the plant gains the nutrients, the symbionts gain the sugars derived from photosynthesis
77
Mycorrhizal fungi as a major symbiont
- most plants
- extensive fungal surface area facilitates nutrient and water uptake
- grow inside the roots and increase surface area for uptake, root system expanded
78
Nitrogen-fixing bacteria as symbionts
- some plants
- bacteroid containing nodules form to facilitate nitrogen fixation
- bulbs on roots
79
Ectomycorrhizal fungi
- proliferate on the outside of the root and between cells
- not very common
- don't penetrate so don't cause damage
- found in forests in association with trees
80
Arbuscular mycorrhizal fungi
- enter the plant cell and form tree-like structures
- the fungus gets sugars produced by photosynthesis
- the plant gets nitrogen and phosphorus from the soil
- the arbuscule provides a large surface area for nutrient exchange
81
Root nodule symbiosis
- bacteria form root nodules
- bacteria live in them
- ensure plants get nitrogen
- mainly within plants of the legume family
82
Nitrogen abundant but unavailable
- in the atmosphere, nitrogen exists as dinitrogen gas N2, an unusually inert molecule with a triple bond holding the two atoms together
83
Biological nitrogen fixation
- uses ATP
| - N2 + 16 ATP + nitrogenase -> 2 NH3
84
Two-way signalling between rhizobia and plant
- the plant root produces a flavonoid chemical that attracts rhizobia
- the bacterium produces a Nod factor, identifying it as a symbiont (and not a pathogen)
- the plant prepares to form a sybiotic nodule structure
- makes sure plant does not activate defences
85
Do all bacteria produce nod factors?
no
86
Decomposition
- dead plant and animal material
- saprophytes (bacteria and fungi)
- recycles back into system
- C and N cycle
87
Saprophytes
- feed off dead/organic matter (plant and animal)
- fungi and bacteria
- digest then absorb
- extracellular (secreted) enzymes
- carbohydratases, lipases, proteases
- essential for C and N recycling
- enzymes usually unique to bacteria and fungi
88
Lignin
- a constituent of the cell walls of almost all dry land plant cell walls
- 2nd most abundant natural polymer
- only polymer in plant cell walls that is not composed of carbohydrate monomers
- only large-scale biomass source of an aromatic functionality
- composed of up to three different phenyl propane monomers
89
Cellulose
- most abundant natural polymer
- has carbon (not easy to extract)
- in the fibres
- works with lignin to provide a structural function
90
Strategies of pathogenicity
- find a host
- gain entry through the plant's impermeable defences
- avoid plant's defence responses
- grow and reproduce
- spread to other plants
91
Interaction -> Disease
- the pathogen must be able to overcome plant defences
- the host plant must be susceptible to the pathogen
- the environment must tip the balance in favour of the pathogen
- most interactions do not lead to disease
92
Facultative pathogens
can attack living plant cells but can also grow by themselves
e.g. on aritficial medium
93
Obligate pathogens
can only grow on their specific living host
94
Biotrophic pathogens
feed on living plant tissue, not causing cell death
e.g. hyaloperonospora arabidopsidis (oomycete)
- live in pretend harmony
- fewer cell wall-degrading enzymes than non-biotrophs
- evade detection and avoid elicitation of defence responses
95
Necrotrophic
kill plant cells and then feed
e.g. botrytis cinerea (fungus)
- 'smash and grab'
- produce toxins and cell wall-degrading enzymes
96
Hemibiotrophic
initially biotrophic and then become necrotrophic
| e.g. pseudomonas syringae (bacteria)
97
Plant viruses and agriculture
- difficult to control
- the more we know, the more we can prevent
- also in tubers
- some plant resistance but not enough
- viruses are biotrophs so need to plan their survival
- can be DNA or RNA but usually RNA
- if they kill cells they can't reproduce
98
Do eukaryotes and bacteria have double or single stranded DNA?
double
99
Viral genomes can be
- dsDNA
- ssDNA (circular)
- dsRNA
- ssRNA(+ or - strand)
- most plant viruses have RNA genomes
- viruses replicate using plant cell materials and machinery
100
Virus transmission by aphids
- aphids = vectors
| - aphids feed on phloem sap using a stylet that they inject into the plants veins
101
Bacterial pathogens: bacterial speck
- pseudomonas
| - hemibiotrophs
102
Bacterial pathogens: crown gall
- agrobacterium
- tDNA integrated into plant chromosome
- biotroph
103
Bacterial pathogens: blackleg
- erwina
- plant cell wall degraded by enzymes
- necrotroph
104
Bacterial pathogens: bacterial wilt
- exopolysaccharide in xylem
| - necrotroph
105
Plant pathogenic nematodes
- globally plant parasitic nematodes cause well over $100 billion in crop losses annually
- very abundant
- infect root system
106
Root-knot nematode
induce expansion in five to seven neighbouring cells to produce giant cells
107
Cyst nematode
partially dissolve cell walls between cells to produce a syncytium
108
Nematode effectors
modify root cells to become specilised feeding cells
109
Rice blast fungus - magnaporthe oryzae
- ascomycete fungus
- major disease of rice
- 10-50% losses of the rice crop
- air-borne disease
- infects foliar (leaf) tissue
- biotrophic
110
Rice blst fungus lifecycle
- sympodial conidia
- conidium falls and spore tip mucilage is secreted
- germling with extracellular matrix
- autophagy occurs and melanizes appressorium
- penetration peg, pit fields and membrane caps on invasive hypha form
111
Late blight - phytophthora infestans
- most serious potato disease
- costing 7 billion euros per year
- threat to global food security
- genetic resistance readily defeated
- up to 20 chemical sprays banned/reducing chemicals
- hemibiotroph
112
Fungal and oomycete hemibiotrophs
- usually make haustoria
| - haustoria remain outside the plant plasma membrane and are specialised for nutrient and signal exchange
113
Haustorial mother cell
flat structure on cell surface which enters cell to form a bulb-like structure (haustorium)
114
Infection hypha
haustorial mother cell on surface enters cell in a rod-like structure
115
arbuscule
hand-like structure from haustorial mother cell
