We can identify developmental genes
by the following comparisons
2. Cell movement
3. Rigidity of the body shape
4. Multicellular stages
The multicellularity of the animals and plants
mechanisms is developed independently.
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.
This is a conserved sequence motif found in
genes which comprise the MADS-box gene
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
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 Genes
M – MCM1 from the budding yeast
A – Agamous from the thale cress
D – Deficiens from the snapdragon
S – SRF from the human
Agamous – is a gene and transcription factor for
the thale cress.
SRF – also known as Serum response factor
Serum response factor
It is a transcription factor that can be found in
It is considered very important especially in the
development of the embryo as it has been linked
to the formation of mesoderm.
1. 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
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 Genes
They are a group of related genes that controls
the body plan of the embryo along the anterior-
posterior (or head-tail) axis.
1. Protein product is a transcription factor.
2. DNA sequence called homeobox is present
3. This are present in animals because of the
same order of the expression along the head-
tail axis of the developing animal.
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
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
Body plan is clearly
determined in most
Highly regulated by
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.
They have haploid
and diploid stages.
Animal life cycle is just one
continuously multicellular stage
Many animals undergo one or more
transformation, when their body plan changes
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
Gametes are formed
They undergo no
gametic meiosis, but
a sporic meiosis.
Animal gametes are formed directly
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.
They set aside
cells in early
No reproductive stem
cells are set aside in
the early development
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.
Longer period of
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
Plants go through a longer period of
Plants during their development do not head for a
distinct body plan.
Many plants grow and develop on and on till they
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
determinated early in
Enormous plasticity in
their development is
Animal cells are determined early in
Animal cells developed into tissues but they are
clearly determined, but in most cases, they are
Most tissues regenerates from stem cells,
however, occurs at some animal species like
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
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:
3. Relative Portions of Vegetative and
That amazing level of plasticity helps plants
compensate for their lack of mobility.