Biology 1B - plants molecular biology Flashcards
(93 cards)
1
Q
why are plants good systems for experiments
A
- don’t create any issues in animal experimentation
- have good knowledge of many plants genes and have tools to study their proteins (structure, function and location)
- were able to regenerate whole plants from single cells in culture (stomatic embryogenesis)
- easy to introduce new genes into plant
2
Q
describe stomatic embryogenesis
A
plant embryo develops from single stomatic cell
single cell from plant => cultured in nutrient medium => single cells in suspension divide => embryonic plant develops => plant cultured in agar medium => planted in soil
3
Q
why is it useful to genetically modify plants
A
- provides tools for experimentation
- can improve crops by overcoming genetic limitations of crops
- can introduce novel genes
4
Q
what are the goals of improving crop resistance
A
disease resistance - reduce use of pesticides
stress tolerance - cold/draught
altered composition of harvested product
5
Q
what are transgenic plants
A
genetically modified plants
6
Q
what is a useful way of genetically modifying plants
A
employing an organism that already genetically modifies plants
7
Q
what is agrobacterium tumefaciens
A
gram negative bacterium that causes grown gall disease (tumours) in plants by transferring its DNA into plant cells
it colonises wound sites on plants (has ability to detect microscopic wounds)
8
Q
describe the genetic info in agrobacterium
A
contains chromosome
contains Ti plasmid
9
Q
describe the role the Ti plasmid has in agrobacterium infecting plant cells
A
- agrobacterium enters wound site and binds to plant cell
-T-DNA region is copied and coated with proteins before transferred to plant cell (allowing it to pass through cell wall barriers) - contains T-DNA (transfer) which is transferred to plant cells nucleus
- T-DNA integrates into plants chromosomal DNA
10
Q
what is the Ti plasmid in agrobacterium
A
- Ti plasmid is required for the ability to infect plants
- it is tumour inducing and contains genetic info allowing it to infect
11
Q
what is genetic transformation
A
direct introduction of new genetic information
12
Q
what is a use of agrobacterium
A
can be used to genetically modify plants
13
Q
what do the genes on T-DNA do
A
- encode enzymes for auxin and cytokinin biosynthesis
this causes abnormal cell division and tumour formation - encode enzymes for opine biosynthesis. opines are small molecules used by agrobacterium for growth
14
Q
how can you modify T-DNA to introduce a foreign gene into plants
A
- delete existing genes and insert new gene (to prevent tumour growth)
- also introduce a selectable marker gene (creates system where you can select genetically modified T-DNA
15
Q
what is a selectable marker
A
- an antibiotic resistance gene provides a selectable marker, it encodes an enzyme that inactivates an antibiotic
- transformed plants survive in the presence of the antibiotic, non transformed plants die
16
Q
describe how agrobacterium is used to genetically modify plants
A
1) cut tissue placed on culture medium and infect with agrobacterium
2) produce callus cells
3) callus cells produce roots and shoots
4) antibiotic selection applied to identify transgenic plantlets
5) plantlets removed for culture
17
Q
what is a problem with using agrobacterium to genetically modify crops and a solution
A
agrobacterium does infect several of the worlds major crops (wheat, rice etc)
solution = shooting DNA directly into plant
DNA coated with microscopic metal particles accelerated into plant tissue by biolistic gun
18
Q
because plants are sedentary, what do they have to do?
A
optimise growth to maximise light capture for photosynthesis
protect themselves against environmental abuses
19
Q
what is a key regulator of plant development
A
light
20
Q
what environmental stresses do plants need to deal with
A
draught
frost
pathogenesis
salinity
(plant must integrate info and respond/adapt)
21
Q
what underpins complexity in plants
A
genetic information
gene and their encoded proteins
22
Q
what are the steps in gene expression
A
gene => transcription => mRNA => Translation => protein
23
Q
what are some proteins encoded for by genes in plants
A
enzymes
ion channels
structural components
Receptors
transcription factors
24
Q
what do transcription factors do
A
regulate expression of genes
important for developmental complexity
25
do cells differ in their genetic information
no, all cells in an individual have the same genetic information
26
since all cells contain the same geneticin formation, how do different cells have different complements of proteins, allowing them to carry out their function?
through differential gene expression
only a fraction of genetic information present in a particular cell is expressed at any one time
27
what is constitutive gene expression
expression in all cells all the time
28
what is the carrot totipotency experiment
shows that any cell in the individual has the genetic information needed to produce the whole plant, showing all cells contain the same (all) genetic information
totipotent carrot cell => growth medium => embryonic plant => full plant (clone)
29
what are the different ways gene expression is regulated
spatial (location)
temporal (when switched on and off)
environmental regulation (external factor influence)
30
what are ways to study gene expression
1 - looking at proteins
2 - detect specific mRNAs
3 - Visualise transcription
31
why study gene expression
to fully understand how plants grow and develop by identifying the functions of all genes and how their expression is controlled
32
how can you study gene expression by looking at proteins
2- dimensional gel electrophoresis
33
how can you study gene expression by detecting specific mRNAs
transcriptome sequencing:
RNA populations converted to cDNA copies and sequenced
software used to monitor abundance of different transcripts in particular tissues at different times and in response to various treatments
34
how can you study gene expression by visualising transcription
using reporter genes
reporter genes are easy to assay and not usually expressed in plants
35
what promoter can be used to visualise transcription to study gene expression
Bacterial B-glucuronidase
its a colourless substrate and gives a blue product
36
what are examples of genes regulated by the environment
light induced genes (e.g. CAB expression stimulated by light)
stress induced genes
touch induced genes
37
what is Arabidopsis thaliana
small flowering plant in the mustard family
used as a model organism in plant biology
38
describe the structure of Arabidopsis thaliana
rossete leaves in circular pattern at base of plant
cauline leaves are shorter and around stem
flowers 3mm in diameter
siliques are long capsules that contains plant seeds
39
describe the life cycle of Arabidopsis thaliana
6 weeks
central stem grows after around 3 weeks
40
describe the reproductive organs in Arabidopsis thaliana flowers
flowers delf pollinate naturally
stamen is ,ale part of flower, responsible for pollen production
gynaecium is female organ and consists of two fused capsules, an ovary with ovules, a style and a stigma
41
what are the beneficial features of Arabidopsis thaliana for genetic experiments
small and easy to grow
rapid generation time
many seeds produced
self fertile but can also be crossed
easy to produce mutants (mutagenesis)
small, well known genome
42
how can you cross two Arabidopsis thaliana plants as they are self fertile
1 - emasculate female plat by removing anthers to prevent self pollination
2 - collect pollen from male plant and transfer to stigma of female plant
43
how gen gene function by investigated in Arabidopsis thaliana
producing mutations individual proteins and observing changes in the plants phenotype
comparing mutant and wild type phenotypes (mutagenesis)
44
what is an example of an examination of a Arabidopsis thaliana mutant altered in development
Glabra (G1) mutant
examined the role of Gl1 gene in the formation of trichomes (fine outgrowths on plants)
surface of rossete leaves in wild type has 3 prolonged trichomes
mutant lacks these
conclude - the function of Glabra 1 protein = transcription factor that regulates formation of trichomes
45
what are trichomes function
defence against herbivores, reduction in water loss by limiting airflow around plant
46
what is phototropism
the directed growth of a plant in response to light
47
how do plants detect light
photoreceptors
48
what happens to Arabidopsis thaliana grown in darkness
darkness - seeds germinate using stored reserves to get above soil, when reaching light seedlings start to photosynthesise to provide energy.
exhausts seed reserves
49
what are 4 photomorphogenic responses in germinating seeds (dark)
suppression of stem elongation
opening of apical hook
separation and expansion of cotyledons
synthesis of chlorophyll
50
how does light control plant development
by regulating gene expression
51
how many genes in seedlings are regulated by light
about 1/3 of genes in genome
52
compare seedlings grown in light vs dark
dark :
long hypocotyl, unexpanded cotyledons
no chlorophyll
light:
short hypocotyl
expanded cotyledons
chlorophyll
53
what is the CAB gene and what is it stimulated by
chlorophyll a/b binding protein gene
encodes proteins that bind to chlorophyll, essential for photosynthesis
stimulated by light
54
how can we monitor temporal changes in gene transcription
visualising sort term changes in transcription
55
what are two examples of hybrid gene fusions that can be used to visualise transcription (study gene expression)
B-glucuronidase
firefly luciferase
1) swap genes coding sequence with reporter B-glucuronidase
assay hybrid gene fusion in transgenic plant, blue colour shoes where promotor is active ( transcription)
2)using CAB gene and less stable reporter to monitor temporal (short term) changes
same process with firefly luciferase
add luciferin in transgenic plant as it reacts to produce light
monitor luciferase activity
CAB promotor causes luciferase expression to rise and fall over 24 hour period
allows to see plant circadian rhythms
56
what features of light do plants detect
light presence/absence
light quantity
light spectral quality
light direction
light duration
57
how many nanometres is blue, red and far red light
blue light: 450-490nm
red light: 620-750nm
far-red light: 700-800nm
58
what are some plant regulatory photoreceptors
phytochromes
cryptochromes and phototropins
59
describe photoreceptor structure
the apoprotein is the photoreceptor protein
the chromophore is attached to the apoprotein and is a small organic molecule that absorbs light
together they comprise the photoreceptor
60
describe phytochrome structure (type of photoreceptor)
the apoprotein binds a linear tetrapyrrole chromophore
61
describe the two photo-interconvertible forms of phytochrome
Pr - present in dark grown plants and illumination with red light produces Pfr
Pfr - form initiates biological responses
many phytochrome controlled responses show red light induction and far-red photo-reversibility
62
what type of photoreceptor regulates CAB gene transcription
phytochrome
63
describe phytochromes (type of photoreceptor)
absorb red and far-red light
exists in two photo-interconvertible forms (Pr and Pfr)
64
what type of light do cryptochromes and phototropins detect
detect UV - A and blue light
65
how do phytochromes detect vegetation shade
vegetation shade creates far-red enriched light which they can detect
shade avoidance response is also controlled by phytochrome
increase in far-red reflection indicates proximity of neighbours and promotes extension growth
66
describe cryptochromes (type of photoreceptor)
bind to flavin and pterin chromophores that absorb UV-A and blue light
they are involved in controlling stem extension, gene expression and flowering time
67
describe phototropins (type of photoreceptor)
bind flavin chromophores that absorb mainly UV-A and blue light as well
control plant responses, including phototropism
68
how do plants protect themselves from UV-B radiation /sunburn
UV-B regulated gene expression
UVR8 photoreceptor detects UV-B and triggers genes to be express that trigger flavonoid biosynthesis
flavonoids accumulate in epidermis and protect against UV-B rays
69
plant growth is indeterminate, what does this mean
they are not limited in lifespan or to a particular size
70
plant growth is modular, what does this mean
follows patterns that are repeated over and over again
71
what is plant morphogenesis dependant on
entirely on cell division and cell lineage
72
plants have plasticity, what does this mean
able to adapt/ alter development "on the fly" (no fixed blueprint for development)
- underpins totipotency in plants
73
what does totipontency mean
the expression of developmental plasticity
74
what does totipotency of plants allow
clonal propagation of plants
75
what does clonal propagation of plants work (carrot)
- cross section of carrot root
- small fragments cultured in nutrient medium, stirring causes single cells to shear off into liquid
- single cells in suspension begin to divide
- embryonic plant develops
- plantlet cultured on agar medium and planted in soil
- adult plants develops
76
describe embryogenesis in plants
globular stage - fifth division and beyond results in cell layers (e.g. protoderm)
heart stage -multiple cell layers, two seed leaves form, apical meristems start to develop
torpedo stage - multiple cell layers and tissue differentiation
77
what is pattern distribution in plant development
It refers to how specific structures, cells, or molecules are arranged or distributed in space during development.
78
what does pattern distribution imply
spatial guidelines for plant growth
79
what is polarity
relates to having direction or different properties at opposing ends
fundamental property of the environment
associated with pattern formation of biological organisms and generally self-perpetuating
80
what is Jaffe's law
provide guiding principles for studying and identifying signal cascades within biological systems
characterize how cells communicate and respond to external stimuli
81
how do you apply Jaffe's law to rest and identify a signal cascade (what are the 4 laws)
1) law of specificity
2) law of amplification
3) Law of integration
4) law of adaptation
82
describe the law of specificity
states that a signal must be recognized by a specific receptor to initiate a cascade
ligand-receptor binding assays can help confirm specificity
83
describe the law of amplification
A single activated receptor often leads to a cascade of intracellular signals, amplifying the response
measure the downstream effect using techniques like Western blotting or fluorescence imaging
84
describe the Law of integration
Signals from multiple pathways can converge to regulate cellular responses
use inhibitors or knockout experiments to see if different pathways influence the same target molecules
85
describe the law of adaptation
Cells can adjust their sensitivity to prolonged stimulation by modifying receptor expression or signalling components
researchers expose cells to persistent stimuli and measure changes in receptor density or activity over time
86
what can trigger signal transduction pathways in plants
light (blue light and red light photoreceptors)
hormones (auxin, steroids etc.)
physical environment (temp, salinity)
pathogens
87
what is signal transduction
process by which cells detect and respond to external signals, converting them into specific cellular responses
small signal = large response
88
what does signal transduction include
stimulus
transduction process/signal cascade
response
89
what is a signal cascade
90
what is a second messenger
91
what are two purposes of secondary messengers
- to amplify this internal (biochemical) signal
- to transfer the signal to the response mechanism
92
how does Ca2+ play a role in signalling
93
