Plants Flashcards
(135 cards)
1
Q
Why are plants good experimental systems?
A
- No ethical issues
- Know all the genes of many plants (study proteins)
- Somatic embryogenesis
- Easy to introduce new genes
2
Q
Somatic embryogenesis
A
Ability to generate a whole plant from a single cell culture
3
Q
Totipotency
A
Ability of cells to generate somatic embryos/differentiate into any type of cell in the plant
4
Q
Why is it good to be able to introduce new genes to plants
A
- Experimentation eg tagging
- Improve crops
2a. disease resistance (no need to spray pesticides)
2b. stress tolerance
2c. altered composition (higher yield, include vitamins etc)
5
Q
Genetic transformation
A
Direct introduction of new genetic information
6
Q
Transgenic plants
A
Genetically modified plants
7
Q
Organism that genetically modifies plants
A
Agrobacterium tumefaciens
8
Q
Describe agrobacterium tumefaciens
A
Microscopic soil bacterium
Motile, flagellum
Sense plant DNA in soil and swims up the concentration gradient
Swims to wound site
9
Q
Ti plasmid
A
Tumour inducing plasmid, responsible for infection
Plasmid replicates independently from chromosome and can be genetically different
10
Q
T-DNA
A
Transfer DNA, region in Ti plasmid
Copied and coated with proteins,
Transferred to plant cell (Nucleus),
Randomly inserted into plant cell chromosome,
Creates permeant change to the genetic makeup
11
Q
Auxin and cytokinin
A
Plant growth regulators by regulating cell division
In high concentrations cause abnormal cell division and tumour formation
12
Q
Opines
A
Small molecules used by Agrobacterium for growth.
Not normally present in plants but agrobacterium infection leads to their synthesis
13
Q
Genes on T-DNA
A
- Encode enzymes for auxin and cytokinin biosynthesis
- Encode enzymes for opine biosynthesis
14
Q
Selectable marker
A
Allows for identification of plants that have and haven’t taken up the gene
15
Q
Example of selectable marker
A
antibiotic resistance gene
it encodes a gene that inactivates an antibiotic
16
Q
- Problem and solution of agrobacterium
A
Doesn’t work on wheat, maize and rice
Shooting DNA into plants: DNA coated microscopic metal particles accelerated into plant tissues
17
Q
- Problem and solution of agrobacterium
A
What, maize and rice are difficult to regenerate in culture
So regeneration from embryos using both bacterium and shooting
18
Q
Genetic complexity (in plants)?
A
Sedentary so need to optimise growth and protect against environmental abuses; respond to biggest perceived threat
19
Q
Differential gene expression
A
only a fraction of the genetic information present in a particular cell is expressed at any one time
- spatial
- temporal
- environmental
20
Q
Constitutive gene expression
A
expression in all cells all the time
21
Q
How to study gene expression
A
- 2D gel electrophoresis to analyse proteins
- Detect specific mRNAs (transcriptome sequencing)
- Visualise transcription
22
Q
Transcriptome sequencing
A
RNA converted into c(opy)DNA and sequenced, then analysed =
23
Q
Reporter genes
A
Method of visualising transcription
- easy to assay
- not usually expressed in plants
24
Q
Example of a reporter gene
A
Bacterial beta-glucuronidase
Turns product blue
25
Promoter gene
Regulates transcription, associates with non-coding regions, reporter genes dependent on it
26
Method of creating transgenic plant with reporter gene
1. Hybrid gene fusion: reporter gene inserted in relation to promoter gene
2. Assay the hybrid gene fusion in a transgenic plant
3. Hybrid gene inserted into agrobacterium T-DNA
4. Transformation
5. Transgenic plant
27
CAB
Chlorophyll a/b binding protein
Expressed only in chloroplast-containing cells (eg in the thylakoids)
Regulated by Pfr
28
Environmental regulation of gene expression
1. Light-induced genes
2. Stress-induced genes
3. Touch-induced genes (stronger and shorter stems)
29
Forward genetic approach
1. Isolate mutant in selected process
2. Identify gene that has become mutated
30
Best plant for genetic research
Arabidopsis thaliana
(temperate weed)
31
Why is Arabidopsis the best plant for genetic research
1. Small and easy to grow
2. Rapid generation time (6 weeks seed-seed)
3. Hundreds of seeds per plant
4. Self fertilisation and can be crossed
5. Easy to produce mutants
32
M1 Generation Arabidopsis
Diploid, heterozygous for mutant genes
5 homologous pairs
33
M2 generation of arabidopsis
1 in 4 chance of being homozygous mutant
34
Why is arabidopsis popular for molecular biology ?
1. Small genome, fully sequenced (allows for isolation of genes
2. Little repetitive or non-coding regions
3. Easy to transform with agrobacterium floral dip
35
Alternative to beta-glucuronidase
Firefly luciferase
Good for visualising short term transcription because it's unstable
Luminesces, photon camera
36
Circadian rhythms
Sequences that happen in accordance with temporal change
eg CAB is regulated by the circadian rhythm; photoreceptive during light and storage genes activated during dark
37
Photoreceptor contents
Apoprotein
Chromophore
38
Apoprotein
Photoreceptor protein,
binds a linear tetrapyrrole chromophore in phytochrome
39
Chromophore
Small organic molecule that absorbs light
40
Phytochrome
Absorbs principally red and far-red light
Exist in 2 photo-interconvertible forms, Pr and Pfr
41
Pr and Pfr
Convert in response to light (phot-reversibility)
Pr: dark-grown plants
Pfr: red light (under canopy), initiates biological responses
42
Neighbours
Increase in far-red reflection indicates proximity to neighbours, promoting extension growth, to grow higher than neighbours
43
Cryptochromes
Control stem extension, gene expression and flowering time
Bind flavin and pterin that absorb UV-A and blue light
44
Protection from the sun
In response to UV-B exposure, UVR8 gene expresses > flavonoid biosynthesis > flavonoids in epidermis
44
Phototrophins
Control plant responses including phototropism (grow towards the light)
Bind flavin chromophores that absorb mainly UV-A and blue light
45
Marasmus
Form of acute hunger, lacking in calories, causes death and disease
46
Kwashiorkor
Form of acute hunger, lacking in protein, causes death and disease
47
Chronic hunger
Only just enough to survive, death and disease
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Hidden hunger
Mineral deficiencies, death and disease
49
UK hunger
Fatigue, lack of concentration, anxiety and depression
50
How to achieve food security
Expand eg farm on marginal land
Intensify eg more yield/land surface/nutritional value
Be smart eg grow the right thing in the right place at the right time, optimisation and management
51
What makes wheat funky
High carbohydrate content
Long storage
Bread
52
What makes wheat funky?
Originally had 7 homologous pairs
But more modern inter-species hybrids have 21
53
Quantitative genetics
links traits to position within a genome
54
Rice
12 diploid chromosomes
Japonica and Indica
Polished before storage, long shelf life
55
Pros and cons of wet and dry rice cultivation
Wet is work intensive, dry allows for machinery/easier
Wet utilises natural weed control and fertilisation
56
Consequences of breeding
Lower allelic diversity and robustness but higher yield
57
Ways to tackle expansion
Extend into potential/marginal land eg (forest) arid
Grow biofuels in the ocean
58
Marginal land
Good land can become marginal due to over-use, salinization, pollution and climate change
59
Secondary salinity
When non-distilled freshwater is used as irrigation but quickly evaporates off leaves salt behind
60
Salt tolerance
Modification to ensure overexpression of antiporter gene NHX1
NHX1 transports Na+ into the vacuole in exchange for H+
61
Yield gap
Difference between potential and actual yield
62
Do abiotic or biotic factors result in more yield loss
Abiotic
63
Effect of CO2 on crop production
More CO2 = more photosynthesis and growth, but result in abiotic stresses, so overall loss in yield.
So need to increase CO2 assimilation and stress resistance
64
ABA
Abscisic acid, stress hormone, produced in roots, leads to the closing of stomata in response to water deficit.
- Less water loss,
BUT
- Reduced CO2 uptake,
- Overheating
65
Plant nature
Are risk-averse so respond prematurely; one dry day can lead to preparing for a drought and a complete stop in growth.
Not ideal for agriculture
66
Resurrection plants
Plants that can recover from near death by accumulating high levels of trehalose (compatible osmolyte) as compatible solute for osmoregulation
67
QLT
Quantitative trait locus
68
GWAS
Genome-wide association studies
69
Indeterminate
Growth is not limited in lifespan or to a particular size. Applies to Plants. Animal growth is determinate
70
What is unusual about plant development
- Plastic
- Modular
- Plant form (morphogenesis) arises within cell walls and therefore depends entirely on cell division
71
Plasticity
Able to adapt/alter development in time
72
Polarity
Having direction different properties at opposing ends; pattern formation in organisms, self-perpetuating
73
Germination forms
Rhizoid (roots) and thallus (body) cells
74
Factors inducing germination
Light, rhizoid to dark
Heat, rhizoid to warm
Osmotic gradient, rhizoid to water
Ph and salt, rhizoid to alkaline and salt
Fertilisation, rhizoid at entry
75
Actin overview
Essential to fix axis
Blocked by toxin cytochalasin B
Underlies cytoplasmic threads
76
Actin + myosin
Interacts with myosin to generate directional force/contraction
Drive cyclosis (cytoplasm movement)
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GF Actin
Actin exists in dynamic equilibrium between globular (G) and filamentous (F) actin
These 'treadmills' generate force without myosin
78
Polarity and cell fate
Root structure arises from stem cell (meristem) divisions that initiate cell files (cell lineage)
79
Cell files
maintained by controlled (Limited) cell divisions
80
How is polarity controlled
Apical-basal polarity is maintained by hormonal gradients, especially auxin
Auxin gradients result from directed transport between cells
81
Efflux carriers
Pin proteins transport auxin out of cells
82
Signal transduction
processes that operate to couple a stimulus to a response
83
Signal transduction requires
- a receptor for the stimulus
- a transduction process/signal cascade to transmit the signal
- a response mechanism to act on the signal
84
Receptor
Recognises a stimulus.
Converts the signal using biochem into a biologically meaningful form
85
Second messengers
Amplify internal biochemical signal
Transfer signal to the response mechanism
86
Stomata
Hydraulic valves in the leaf epidermis that permit CO2 entry for photosynthesis
87
Guard cells
surround the stoma to regulate its size, balancing the need for CO2 against the prevention of water loss
88
Virtual water
The exportation of water in the form of manufactured items
89
Guard cells and turgor
Uptake of solute/water increases turgor which increases the volume of the guard cells and they bow out/open
90
What does ABA control
K+ to flow in and out of K+ channels
Cl- to flow out of Cl- channels
91
Voltage clamping
Patch Clamp technique
Measure ion channel activity
Measure single protein function
92
Ion channel proteins include
1. A selectivity filter to separate ion species
2. A gate that rapidly opens and closes
93
Gating
Changes in protein conformation in the ion channel and can be seen as very small steps in current
94
1st requirement of Jaffe's Law
Stimulus, 2nd messenger and response must be related in time and space
95
2nd requirement of Jaffe's Law
Blocking a signal/messenger must block signal and response downstream
96
3rd requirement of Jaffe's Law
Introducing a 2nd messenger without the primary stimulus must give the response downstream
97
Where does calcium originate?
95% comes from intracellular stores
5% from external sources
98
ABA and calcium
Ca2+ rises after ABA treatment and before stomatal closing and prolongs Ca2+ increase
Jaffe's 1st rule
99
Example of Jaffe's 2nd rule
Buffering Ca2+ in the cytosol suppresses ABA action on flow of K+ into, and Cl- out of the cell.
But there's no change in K+ out of the cell, implying additional signal cascades
100
Example of Jaffe's 3rd rule
Adding Ca2+ mimics the effect of ABA into the cell
101
What % of crop loss is due to biotic factors?
40%
102
Current solution to bacterial diseases
Introduction and breeding for genes which confer a resistance. However genes are not always available/viable for introduction
103
What % of plant diseases are viral
50%, often transmitted by vectors
104
Name the organism and disease that caused the Irish Potato Famine in the 1840s
Phytophthora infestans
Late Potato Blight
105
Phytophthora infestans
Causes the foliage/leaves to rot and fall off within 2-3 weeks. Causes the potato to rot also.
Can evade/overcome resistance.
106
Necrotrophs
Pathogens which grow in dead tissues.
Use nutrients released by growth to secrete cell-degrading-enzymes to kill host cells
107
Biotrophs
Pathogens which live in living tissue.
Communicate with host cells. Use nutrients released for growth to extract nutrients
108
Innate immunity
the ability of plants to recognise and defend themselves against pathogens is inherited via genes
109
PAMPs
Pathogen Associated Molecular Patterns, such as flagellin
110
Basal immune system
(Applies to both plants and animals)
Plant cells carry proteins on the outside of the plasma membrane that can recognise macromolecules associated with pathogens
Contain slowly evolving PAMPs
111
Gene-for-gene immune response
Proteins encoded by resistance genes, within the cells, recognise pathogen-specific effector molecules and activate defence responses
112
Gene-for-gene hypothesis
For resistance to occur, complementary pairs of dominant genes must be present in the host (resistance) and pathogen (avirulence)
113
Avirulence genes
Encode proteins that are essential for the pathogen to invade and grow in the plant host
114
Effectors - avirulence genes
Injected into host cells by bacterial and fungal pathogens.
They control host defence responses and are essential for infection.
115
R-genes
Resistance genes.
Evolved by plants to encode proteins that recognise these effector molecules and trigger rapid defence responses
116
SAR
Form of defence response, including activating: Systemic acquired resistance.
Elicited most strongly by gene-for-gene responses.
Salicylic acid acts as signalling molecule.
= Reduced susceptibility to subsequent infection by either virulent or avirulent pathogens
117
Issues with R genes
A few years after breeding them in, there is a loss of resistance due to genetic drift
118
Conventional resistance
the use of genetic manipulation methods to introduce existing resistance genes into cultivars or species in which they do no naturally occur
119
Novel resistance
the use of genetic manipulation methods to introduce genes that function to limit pathogen spread by mechanisms other than via conventional resistance
120
Simplot innate potatoes
1. Two R-genes from wild Solanum spp confering resistance to Phytophthora infestans
2. One R-gene, Ry confers resistance to Potato Virus Y
3. Expressing an oligopeptide which is toxic/inhibitory to Potato cyst nematode
121
BT toxin
Crystalline proteins produced by the gram negative bacteria: bacillus thuringiensis.
Proteins show species-specific toxicity to insect larvae.
122
Bt toxin in transgenic plants
Genes encoding the Bt Toxin can be inserted into plants using agrobacterium or biolistics.
Expression of the appropriate protein gives plants that are toxic to the target larvae
eg against European Cornborer larvae
eg Cotton bollworm in India
123
Benefit of Bt toxin over neonictonoids
Neonictonoids are toxic to bees, Bt toxin has negligible toxicity.
124
How many genes can a single Bt maize line produce
8.
Gives added protection against resistance developing in the pest
125
Canola/oilseed rape
A line of brassica (tolerant to low temperature) napus, isolated from rapeseed lines with low erucic acid levels, which were developed in the 50s
126
Eurcic acid in canola
Have been reduced by mutagenesis and conventional breeding
127
Manipulating plant lipids
Increase the concentration of healthier monounsaturated fatty acids, over polyunsaturates/saturates
Increase the ration of high to low density lipoprotein in blood
128
Novel fatty acids
have industrial applications and plants can be engineered to produce them cheaply, and more benignly than through petrochemical industry
129
Qualities of PDP
Plant Derived Proteins
- Commercially useful
- For medical treatments
- Vaccines
- Anti-disease drugs
130
Monoclonal antibodies
B-lymphocytes from mice can be 'immortalised' generating clonal lines.
Genes from suitable monoclonal cells can be cloned and expressed in plants
131
mAbs
Monoclonal antibodies for treatment of human health problems
132
Zmapp
Treatment for ebola, 2013
3 monoclonal antibodies against the viruses 'spike proteins'.
Antibodies initially generated as mouse monoclonals. Expressed in Nicotiana benthamiana
133
Benefit of mAbs in transgenic plants over mammalian cell cultures
Can be carried out in containment areas, so no contamination,
Cheaper,
Ability to scale up
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