Week 13 L4: Plant Reproduction - ABCE Model Flashcards
What combination of genes make a sepal?
A
What combination of genes makes a petal?
A+B
What does genes B+C make?
stamen
What does gene C make?
Carpel
Where are the genes encoding key TF found?
floral meristem
What encodes the TF needed for specificity of floral organs?
ABC (+E model)
What are the MADS box genes?
once activated by TF (encoded by ABCE genes) it creates a specific plant organ
What is the arrangement of MADS box genes and CArG for floral development?
The MADS box genes encode TF factors which bind to DNA at a specific transcription activation site.
Depending on the combination of MADS TF to a specific CArG will initiate a specific transcription to a plant organ
What gene is needed in each quartet model for organ formation?
E genes (sepalata genes) SEP
What is CArG?
The DNA motif bound by MADS box proteins
What does the quartet model only apply to?
highly derived eudicots like arabidopsis
What creates variation in plants flower formation?
Differences in MADS box genes and where they are expressed may explain in part of how flowers evolved and diversified.
How do MADs box genes interact with one another?
via MADs box proteins
What binds to MADs box genes in plants?
The genes which contain this motif are called the MADS-box gene family. … The MADS domain binds to DNA sequences of high similarity to the motif CC[A/T]6GG termed the CArG-box.
What do the MADs box genes create?
TF
AP1, AP3, PI, AG & SEP
What do the MADs box proteins bind to?
CArG-box of TARGET dna
What part of the MADs box TF bind to the CArG-box motif?
MADs domain on the protein
DNA binding CArG box
What is the quartet model?
A combination of 4 MADs box genes biding to CArG seq
What combination of quartet model TF interact to make carpels?
AG (C) + sep
What CArG does the AG/SEP TF interact with?
CArG1
What combination of quartet model TF makes a stamen?
SEP/AG
PI/AP3
What CArG gene does PI/AP3 bind to?
CArG2
What combination of TF makes a petal?
AP1/SEP
PI/AP3
What CArG gene does AP1/SEP bind to?
CArG3
What combination of TF makes a sepal?
AP1 and SEP
What are the 3 different combinations of TF pairs?
AG/SEP - CARG1
PI/AP3 - CARG2
AP1/SEP - CARG3
How many MADs do proteins to MADs box gens have?
some have nearly 100 diff MADS proteins
What plant types have the ABCE model?
gymnosperms and angiosperms
What is a basal angiosperm?
sporophyte dominant
enclosed gametophyte
What is the most basal angiosperm?
amborella
Is a amborella have both male and female plants?
YES
What is a special feature of a female amborella?
it has a staminode
and tepal
What is a staminode?
it looks like a stamen but is actually not
It’s a female flower.
Thus it can attract pollinators as the stamen produces pollen. It tricks the insect to giving the plant pollen by what is on it bod
What is a tepal?
not quite a petal not quite a sepal
What kind of structure is the tepal?
Sterile
perianth structure
What is a perianth structure?
non-reproductive (accessory, sterile) part of the flower, consisting of floral leaves surrounding the androecium and gynoecium. It is differentiated into outer and inner whorls.
What does sterile mean?
unable to produce viable offspring
What can change in the ABC model to produce petal-like sepals in the basal eudicot - clematis integrifolia?
limiting the location of B gene expression can result in plants with no true petals.
The model predicts that the B gene would be reduced so that it never overlaps with A
Resulting in 2 whorls with sepals due to B gene under-expression.
What would A with no B result in?
two whorls with sepals
What would the over-expression of B gene result in?
Many petals
What is a feature of the Clematis integrifolia species?
petal-like sepals
NO trie petals
What is a feature of C. chiisanensis?
separate whorls of pateloid sepals and true petals. over-expression of B class genes
How do we know that the b class gene is overepressed in Clc clematis?
The APIII IN Clc is highly expressed on assay and the AP3 is absent in the Cli plant
What ABC model does a tulip have?
Over expression of B gene forming tepals
What is the feature of tulips and their gene expression?
A genes are only expressed with B genes, resulting in 2 whorls of petal-like organs
What whorls are B gnes expressed in in tulips?
outer and inner tepal (whorls 1&2) as wells as the stamen (whorl 3
What is the ‘Fading borders’ model?
In contrast, in the fading borders model, the borders between A, B, and C functions are blurred to produce a gradual transition of organ identity programs across the floral meristem. Hence, floral organs are influenced by “ABc,” “aBC,” and “abC” activities, where lowercase font indicates lower functional influence.
What is the blurred boundaries of the genes in the ABC model known as?
fading borders model
What would A(faded)Bc create?
sepaloid tepal
What does the ABCE model only apply to?
highly derived eudicots like arabidopsis
What are the MADs box gene expression in the gymnosperm (conifer) between male and female cones?
F : C
M : B+C
How is the presence of a common ancestor thought by the gymnosperm and angiosperm? EVO
the cone and flowers respectively are both formed by the interaction of B and C function genes, implying presence in common ancestor
What is the ‘out of female’ hypothesis? EVO
B function genes became expressed to generate stamen-like structures from carpel-like organs (male derived form female) - not clear
What are the A and E genes called/function? EVO
act as meristem identifiers - make the reproductive structure more recognisable as a “flower” to us
What type fo plant only truly differentiate petals and sepals?
only higher eudicots e.g. arabidopsis
What level of plant shows varying degrees of differentiation and what structures do they create?
lower eudicots
monocots
basal angiosperm
Differentiation of petaloid and sepaloid organs from leaf-like structures
what are the petal-like structures in grasses?
lodicule
What is an example of a grass?
rice flowers
How does grass pollinate?
wind
What is the importance of lodicule swelling in rice?
Important in agronomics
potential for outcrossing
What is the effects in pollen exchange due to loss of lodicule swelling?
fewer pollen grains exchange since florets do not open.
