Key Events in Early Development

Question 1

What does embryogenesis start and finish with?

Answer 1

With the zygote and end with the adult pattern of organ formation

Question 2

At what day does the human embryo have all the human organs in an established pattern?

Answer 2

56 days

Question 3

In animals embryogenesis establishes pattern formations but what happens in plants?

Answer 3

Embryogenesis leads to the production of immature/rudimentary structures which means further development is required

Question 4

Where does plant embryogenesis take place?

Answer 4

The seed

Question 5

What are the three stages of plant embryogenesis?

Answer 5

1. Morphogenesis
2. Maturation
3. Descication

Question 6

What is involved in morphogenesis?

Answer 6

The development of rudimentary organs

Question 7

What is involved in maturation?

Answer 7

The plant acquires resources to help it survive dormancy

Question 8

What is involved in desication?

Answer 8

The embryo dries out and goes into dormancy

Question 9

What does the zygote divide into?

Answer 9

An apical cell and a basal cell

Question 10

What does the apical cell go on to be?

Answer 10

The embryo cells

Question 11

What does the basal cell go on to be?

Answer 11

The suspensor ( the stalk )

Question 12

What is stage 1 of morphogenesis?

Answer 12

Formation of the mutlicellular embryo?

Question 13

What are the steps in stage 1 of morphogenesis?

Answer 13

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

Question 14

What is stage 2 of morphogenesis?

Answer 14

Formation of the globular embryo

Question 15

What are the steps in stage 2 of morphogenesis?

Answer 15

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

Question 16

What is stage 3 of morphogenesis?

Answer 16

The formation of the heart shaped embryo

Question 17

What is involved in stage 3 of morphogenesis

Answer 17

The embryo cells ontop of the suspensor are now in a heart shape and have developed multiple layers

Question 18

What are the three cell layers of the heart stage embryo

Answer 18

L1 = epidermal
L2 = Vascular tissue
L3 = Cortex

Question 19

What is stage 4 of morphogenesis?

Answer 19

Formation of the torpedo shaped embryo

Question 20

What happens in the 4th stage of morphogenesis?

Answer 20

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

Question 21

What specifies the differential fates of the apical and basal cells?

Answer 21

The spatial patterns of gene expression

Question 22

What are three transcription factors present in the zygote before cell division?

Answer 22

WOX2, WOX8 and WOX9

Question 23

When the zygote divides inthe apical and the basal cell where do the transcrption factors go?

Answer 23

WOX2 is localised in the apical cell and WOX 8 and WOX9 are localised in the basal cell

Question 24

Why are WOX 8 and 9 mutants altered in apical cell development as well as basal?

Answer 24

Because they regulate the expression of wox2 in the apical cell

Question 25

What is auxin?

Answer 25

A hormone that is a plant growth regulator

Question 26

What is polar auxin transport?

Answer 26

When the auxin hormone is transported through the plant in a polar way from the apical cell to the basal

Question 27

After the first cell division of the zygote into the apical and basal cell what is the concentration of auxin in the two cells?

Answer 27

The apical cell has a high auxin concentration and the basal cell has a low auxin concentration

Question 28

How can you show that auxin is involved in morphogenesis of the plant?

Answer 28

If you use mutants e.g. extra auxin in the basal cell or inhibited auxin transport they have disrupted development

Question 29

What is the phenotype of mutants in auxin transport?

Answer 29

Gnom mutants

Question 30

What transports auxin in the polar auxin transport?

Answer 30

PIN proteins

Question 31

How do pin proteins make the auxin transport in a polar way?

Answer 31

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

Question 32

How are is WOX2 related to the pin proteins that are invoved in polar auxin transport?

Answer 32

They regulate the expression of the PIN proteins

Question 33

What happens during maturation?

Answer 33

They seed prepares reserves for dormancy like carbohydrates proteins and lipids by undergoing lots of gene expriession

Question 34

Where are the reserves stored in maturation?

Answer 34

Cotlydeons or endosperm

Question 35

What does the embyro have to do in descciation?

Answer 35

The mature embryo loses water and dries out

Question 36

Why is it important that desiccation is managed?

Answer 36

So the embryo can reassimilate water and continue normal growth so you cant damage the embryo or the proteins in it

Question 37

What genes are involved in regulating desiccation?

Answer 37

Late embryogenesis abudant genes (LEA genes)

Question 38

Where can you find LEA proteins?

Answer 38

In ressurection plants

Question 39

Apart from LEA proteins what are other proteins related to dehydration?

Answer 39

Dehydrins

Question 40

What is it about LEA proteins and dehydrins that mean they are useful in dessication?

Answer 40

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

Question 41

What is Abcisic acid?

Answer 41

Promotes the expression of LEA genes

Question 42

What is the phenotype of mutants in ABA?

Answer 42

They have no perioid of dessication and germinate straight away