Key Events in Early Development Flashcards
What does embryogenesis start and finish with?
With the zygote and end with the adult pattern of organ formation
At what day does the human embryo have all the human organs in an established pattern?
56 days
In animals embryogenesis establishes pattern formations but what happens in plants?
Embryogenesis leads to the production of immature/rudimentary structures which means further development is required
Where does plant embryogenesis take place?
The seed
What are the three stages of plant embryogenesis?
- Morphogenesis
- Maturation
- Descication
What is involved in morphogenesis?
The development of rudimentary organs
What is involved in maturation?
The plant acquires resources to help it survive dormancy
What is involved in desication?
The embryo dries out and goes into dormancy
What does the zygote divide into?
An apical cell and a basal cell
What does the apical cell go on to be?
The embryo cells
What does the basal cell go on to be?
The suspensor ( the stalk )
What is stage 1 of morphogenesis?
Formation of the mutlicellular embryo?
What are the steps in stage 1 of morphogenesis?
the zygote undergoes cell divisions to become the apical and basal cell which divide into 4 cells, then they produce the suspensor and the embryo
What is stage 2 of morphogenesis?
Formation of the globular embryo
What are the steps in stage 2 of morphogenesis?
The fifth cell division leads to a 16 cell globular cell ball ontop of the suspensor which then go on to form layers that are different and will ultimately become different things
What is stage 3 of morphogenesis?
The formation of the heart shaped embryo
What is involved in stage 3 of morphogenesis
The embryo cells ontop of the suspensor are now in a heart shape and have developed multiple layers
What are the three cell layers of the heart stage embryo
L1 = epidermal L2 = Vascular tissue L3 = Cortex
What is stage 4 of morphogenesis?
Formation of the torpedo shaped embryo
What happens in the 4th stage of morphogenesis?
The embryo cells have formed a torpedo shape and the cell layers that were seen in the heart shaped embryo have began to differentiate and produce tissues like the cotyeledons and the rod and shoot meristems
What specifies the differential fates of the apical and basal cells?
The spatial patterns of gene expression
What are three transcription factors present in the zygote before cell division?
WOX2, WOX8 and WOX9
When the zygote divides inthe apical and the basal cell where do the transcrption factors go?
WOX2 is localised in the apical cell and WOX 8 and WOX9 are localised in the basal cell
Why are WOX 8 and 9 mutants altered in apical cell development as well as basal?
Because they regulate the expression of wox2 in the apical cell
What is auxin?
A hormone that is a plant growth regulator
What is polar auxin transport?
When the auxin hormone is transported through the plant in a polar way from the apical cell to the basal
After the first cell division of the zygote into the apical and basal cell what is the concentration of auxin in the two cells?
The apical cell has a high auxin concentration and the basal cell has a low auxin concentration
How can you show that auxin is involved in morphogenesis of the plant?
If you use mutants e.g. extra auxin in the basal cell or inhibited auxin transport they have disrupted development
What is the phenotype of mutants in auxin transport?
Gnom mutants
What transports auxin in the polar auxin transport?
PIN proteins
How do pin proteins make the auxin transport in a polar way?
They can localise in the membranes but they dont just localised in all membranes they localise in ones that allows the auxin to be transported only to the cell below it
How are is WOX2 related to the pin proteins that are invoved in polar auxin transport?
They regulate the expression of the PIN proteins
What happens during maturation?
They seed prepares reserves for dormancy like carbohydrates proteins and lipids by undergoing lots of gene expriession
Where are the reserves stored in maturation?
Cotlydeons or endosperm
What does the embyro have to do in descciation?
The mature embryo loses water and dries out
Why is it important that desiccation is managed?
So the embryo can reassimilate water and continue normal growth so you cant damage the embryo or the proteins in it
What genes are involved in regulating desiccation?
Late embryogenesis abudant genes (LEA genes)
Where can you find LEA proteins?
In ressurection plants
Apart from LEA proteins what are other proteins related to dehydration?
Dehydrins
What is it about LEA proteins and dehydrins that mean they are useful in dessication?
They contain lots of charges so are extremely hydrophillic which means they carry out the function of water when there is none and can protect the membranes and our components of the cell by forming a charged layer around them
What is Abcisic acid?
Promotes the expression of LEA genes
What is the phenotype of mutants in ABA?
They have no perioid of dessication and germinate straight away
