Somatic embryogenesis, stages involved in somatic embryogenesis, its uses and applications.

1. Renjimol Raveendran
Junior Research Fellow-DBT
Biotechnology and Bioinformatics Division,
Jawaharlal Nehru Tropical Botanic Garden and Research
Institute,
Thiruvananthapuram

2. Embryogenesis is a specialized mode of development
by which a fertilized egg through a series of
predetermined pattern of cell divisions and
differentiation forms an embryos, the precursor of the
next generation.
Embryogenesis is restricted to ovule and involves the
fusion of male (sperm) and female (egg) gametes.
Somatic embryogenesis- process of development of a
bipolar structure like zygotic embryo from a non-
zygotic somatic cell.
INTRODUCTION

3. Somatic embryo: is an embryo derived from a
somatic cell, other than zygote usually on culture In
vitro.
Somatic embryo does not have vascular connections
with tissue from which it develops.
Embryos from pollen called androgenic or pollen
embryos & from zygote called zygotic embryos.
Somatic embryogenesis has been projected as the
future method of rapid cloning of plants because:
(a). the embryos are bipolar with root and shoot
primordia, and
(b). they can be converted into synthetic seeds
by encapsulation in biodegradable
substances for direct field planting.

4. Haberlandt conceptualized in the early 1900s that a
vegetative cell could form an embryo.
Somatic Embryogebesis was first demonstrated in the
cell suspension culture of carrot by Steward and co-
workers from USA & Reinert from Germany in 1958.
By 1978, SE reported from 80 species belonging to 33
families.
HISTORY

5. DEVELOPMENTAL PATTERN OF SE
Divide to form a group of
meristematic cells
Meristematic mass continue to divide and form
globular (round-ball shaped)
Heart-shaped
Torpedo shaped
Cotyledonary stage
These cells break the cytoplasmic connections
and become isolated
Cutinization of outer walls
Originate from single cell

6. Single cell Meristematic
cells
Isolated cells Cutinized cells
Globular
Embryo
Heart-shaped
Embryo
Torpedo shaped
Embryo
Cotyledonary
stage

7. This is called Indirect Somatic Embryogenesis (With
callus).
Direct Somatic Embryogenesis
Somatic Embryogenesis directly from explant with
out callus phase.
Direct SE can be induced by supplementing various
concentrations of Auxins and Cytokinins.
Major disadvantage of somatic embryogenesis; an
intervening callus phase which can induce variability

8. SCHEMATIC REPRESENTATION OF EVENTS IN
SOMATIC EMBRYOGENESIS

9. SOMATIC EMBRYOGENESIS VS. ZYGOTIC
EMBRYOGENESIS

10. GENE ACTION IN SOMATIC EMBRYOGENESIS

11. Nitrogen Concentration: NH4+ is necessary for somatic
embryogenesis in cell and callus cultures.
Maltose has especially been found superior to sucrose
in promoting somatic embryogenesis in soybean,
alfalfa and rubber.
Hormone: Auxin and Cytokinin.
For inducing somatic embryogenesis, 2,4-D is an
important factor. Dicamba has been used for monocots
whereas picloram has been effective for legumes.
Ethylene generally inhibits growth and differentiation
but in some cases, promotes somatic embryogenesis.
Eg:- maize.
FACTORS AFFECTING SOMATIC EMBRYOGENESIS

12. ABA treatment, exposure to high sucrose
concentration and gradual desiccation are some of the
treatments known to promote maturation of somatic
embryos.
Polyamines; derived through decarboxylation of amino
acids, have been used to promote organogenesis/
somatic embryogenesis. Putrescine has proved most
effective.
Explant: The choice of explant is generally limited to
immature or less differentiated tissues such as
hypocotyl segments, young leaves, embryonic shoot
tip, young floral parts and immature zygotic embryos.
Genotype: SE vary with genotype.
Medium: MS medium (70% success rate), rarely White’s
or SH basal medium were used.

13. Easy handling and transportation
Potential long-term storage
Higher scale-up capacity
Uniformity in production
Potential for automation of the entire production
process.
ADVANTAGES OF SOMATIC
EMBRYOGENESIS

14. Improvement of crop plants through manipulation at the
cellular level (somatic hybridization, mutation of isolated
single cells, and genetic transformation).
Large-scale multiplication of important plants.
It is possible to induce somatic embryogenesis in
majority of crop and forest plants, and considerable
success has been achieved in scaling up the process.
Somatic embryos can be encapsulated to obtain
synthetic seeds.
Somatic embryogenesis is easily observable, its various
culture conditions can be controlled and a very large
number of somatic embryos can be obtained.
APPLICATIONS OF SOMATIC EMBRYOGENESIS