Developmental Biology Report prepared by:

John Michael P. AngeloRegistered Professional Teacher

SNCECM Math CoordinatorMAT-Biology Student

Identifying Developmental Genes

Genes that are developingAnimals PlantMouse (Mus

musculus)Zebrafish (Danio

reno)Fruit fly (Drosophila

melanogaster)C. elegans

(Caenorhabditis elegans)

African clawed frog (Xenopus laevis)

Chick (Gallus gallus domesticus)

Thale cress (Arabidopsis thaliana)

Maize (Zea mays L. spp. mays)

Snapdragon (Antirrhinum)

Petunia (Petunia hybrida)

Physcomitrella patens (physcomitrella patens)

We can identify developmental genes by the following comparisons1. Multicellularity2. Cell movement3. Rigidity of the body shape4. Multicellular stages5. Meiosis6. Germline7. Morphogenesis8. Plasticity

MulticellularityThe multicellularity of the animals and plants

mechanisms is developed independently.Explanation:That mechanism in the comparison of the

genes between the animals and plants makes up the body plan of plants and animals.

While the homeobox and MADS box genes existed in last common ancestor, the MADS box gene plays the role of regulation of plant development while the homeobox genes are important in animals.

MADS-Box GenesThis is a conserved sequence motif found in

genes which comprise the MADS-box gene family.

This box encodes the domain of DNA-binding MADS. This domain allows to bind DNA sequences of high similarity to the CC[A/T]6GG motif known as CArG-box.

The domain of DNA-binding MADS are called transcription factors.

According to various researchers, the lengths of this box were in the range between 168 to 180 base pairs and that is the encoded MADS domain which has the length of 56 to 60 amino acids.

The MADS domain is evolved, according to some evidences, that there is a sequence stretch of a type II topoisomerase (or cutting of both strands of the DNA helix simultaneously in order to manage DNA tangles and supercoils) in a common ancestor of all extant eukaryotes.

The name of the MADS-Box GenesM – MCM1 from the budding yeastA – Agamous from the thale cressD – Deficiens from the snapdragonS – SRF from the human

Agamous – is a gene and transcription factor for the thale cress.

SRF – also known as Serum response factor

Serum response factorIt is a transcription factor that can be found

in humans.It is considered very important especially in

the development of the embryo as it has been linked to the formation of mesoderm.

Function1. In animals, they are involved in muscle

development, cell proliferation and differentiation. This ranges from the pheromone response to arginine metabolism.

2. In plants, they are involved in controlling all major aspects of development especially in the development of gametophytes, embryo, seed, root, flower and fruits in both male and female.

3. They have homeotic functions like the homeobox (or HOX) genes of animals. While Agamous and Deficiens for the plants participates in the determination of floral organ identity according to the ABC model of flower development.

4. The flowering time determination is also a factor in the MADS-box gene. It has been shown to have an important role in the integration of molecular flowering time pathways.

The genes of the 4th function are essential for the timing of the flower bloom correctly and fertilization helps to ensure it at the time of the maximum reproductive potential.

Homeobox or Hox GenesThey are a group of related genes that

controls the body plan of the embryo along the anterior-posterior (or head-tail) axis.

Properties:1.Protein product is a transcription factor.2.DNA sequence called homeobox is present3.This are present in animals because of the

same order of the expression along the head-tail axis of the developing animal.

Cell Movement

Animals Plants

Motile animal cells Positionally fixed plant cells

Animal cells are motile.The tissues may be folded and moved

against each other easily.On the gastrulation of metazoan, triple

layered system is built (first layer – entoderm, second layer – mesoderm, third layer – ectoderm)

They may even move to other sites autonomously.

Plant cells are positionally fixed.They are trapped in cells which are filled

with rigid walls that are made of cellulose which prevents the movement of cells and tissues.

The plants form three basic tissue systems without gastrulation (1st layer – dermal, 2nd layer – ground and 3rd layer – vascular).

Rigidity of the body shape

Animal Plants

Body plan is clearly determined in most parts

Highly regulated by the environment

Animal body plan is clearly determined in most parts.In different life stages, they are mostly

clearly determined by its genes.If for example, they change their

movement to another place or change their short and long term behaviour, the body plan may change.

Plant development is highly regulated by the environment.They are in variation and characterized by

multiple times occurs also in iterative structures.

The organ proportions and frequency may vary.

Multicellular stages

Animals Plants

One continuously multicellular stage

They have haploid and diploid stages.

Animal life cycle is just one continuously multicellular stageMany animals undergo one or more

transformation, when their body plan changes dramatically.

Life cycle of all plants have haploid and diploid stages.That life cycle is called alternation of

generations.

They are leading to two different body plants during their life cycle (sporophyte and gametophyte)

Meiosis

Animals Plants

Gametes are formed directly through meiosis.

They undergo no gametic meiosis, but a sporic meiosis.

Animal gametes are formed directly through meiosis.There is nothing that could be compared to

the gametophyte in plants.

Plants undergo no gametic meiosis, but a sporic meiosis.The plants produces spores instead of

gametes.Gametophyte is first formed by mitotic

divisions, then forms the gametes.

Germline

Animals Plants

They set aside reproductive stem cells in early development.

No reproductive stem cells are set aside in the early development of plants.

Animal species set aside reproductory stem cells in early development.This decreases the accumulation of

mutation.

No reproductory stem cells are set aside early in development in plants.Some plants live still certain meristems or

meristem parts more inactive till the gametophyte is to be formed.

Morphogenesis

Animals Plants

Distinct, complete body shape

Longer period of morphogenesis

Animals develop to a distinct, complete body shape.Some reorganization may take place during

the animal life stages.In seldom cases, new structures will

develop.Other animals develop stepwise into

different shapes.

Plants go through a longer period of morphogenesis.Plants during their development do not

head for a distinct body plan.Many plants grow and develop on and on

till they die.Meristems which are areas of actively

dividing undifferentiated cells allows for iterative growth and the formation of more and more new organs and structures during a plants life.

Resemblance of embryonic stem cells in animals is present yet continually existing during adult life stages.

Plasticity

Animals Plants

They are determinated early in development.

Enormous plasticity in their development is present.

Animal cells are determined early in developmentAnimal cells developed into tissues but

they are clearly determined, but in most cases, they are irreversibly determined.

Most tissues regenerates from stem cells, however, occurs at some animal species like Ambystoma mexicanum.

Plants show an enormous plasticity in their development.Axillary meristems often grows out in order

to substitute for the lost part.Strategies resembles the regeneration of

the limb in some animals.Whole plants can be regenerated from

single cells.Form of a plant is strongly affected by

environmental factors such as light and temperature, results in great variety of morphologies from the same genotype.

Plant forms affected by environmental conditions could be of:1. Branching2. Height3. Relative Portions of Vegetative and

Reproductive Structures

That amazing level of plasticity helps plants compensate for their lack of mobility.