Seed Storage Proteins in Plants - Improved Nutritional Quality in Seeds # Types of Seed Storage Proteins

1. D r . D i v y a S h a r m a
A s s i s t a n t P r o f e s s o r
SEED STORAGE PROTEINS
A Biodiction (A Unit of Krishna Academy)

2. PLANTS WITH IMPROVED QUALITY OF
NUTRITION
• Improved quality of seed storage proteins by tailoring particular
amino acids have major health benefits for humans and economic
benefits for poultry industries.
• A major target has been increasing Lysine and Methionine content
in particular group of plants.
• Generally, human requires certain essential amino acids (atleast
eight) that are supplied by the diet. Since these are present in
proteins they must by supplied by different foods because one or
another essential amino acids may be below the required level.
• Engineering of plant seed storage proteins for high value amino
acids are highly desirable considering nutritional quality of poorly
fed people from developing countries. This is because people from
these regions rely on a single staple food such as corn or rice.

3. SEED STORAGE PROTEINS
• Plant seeds contain storage a protein varies from 10% (cereals) to 40%
(legumes and oil seeds) of the dry weight.
• Vast majority of the individual proteins present in mature seeds have
structural roles or metabolic in function.
• Majority of the seeds may also contain one to many groups of proteins
serve as huge amino acid reservoir for use in germination and the
process of seedling growth.
• These seed storage proteins reflect not only the total protein content of
particular species but also quality of the protein, in turn can be assigning
to nutritionally or low profile proteins.
For example: Low content of Lysine, Thrionins and Tryptophan in various
cereals seeds and Cysteine and Methionine in legume seeds. These inturn
limit the nutritional quality of the seeds in some purpose.

4. CHARACTERISTICS OF SEED STORAGE
PROTEINS
• Some of the characteristic of seed storage proteins is that are
specifically synthesized and accumulates in the endosperm of
monocots or in the cotyledons and embryo of dicots.
• Their presences in mature seeds in discrete deposited are called
Protein Bodies.
• One of the earliest and first isolated proteins is Wheat Gluten and
Brazil nut Globulin.
• They are synthesized at high levels in apecific tissues and at certain
stages of development.
• Their synthesis is regulated by nutrition and they act as sink for
surplus nitrogen.

5. Albumin
Storage
Protein
• Water
Soluble
Globulins
• Dilute Salt
Soluble
Prolamins
• Alcohol-
water
mixture
soluble
Glutelins
• Dilute acid
or alkali
Classification of proteins in to their groups is based on their
solubility.
Osborne’s classical definitions: 3 protein groups have been
categorized during classification.
Classification of Proteins

6. 2S Albumin
• Napin
• Conglotin
• Sunflower SFAS
• Castor bean
albumin
• Sunflower albumin
Globulin
• 11S Globumin
• 7S Globulin
Prolamin
• Ƴ-gliadin (S-rich)
• C-hordein (S-poor)
• HMW subunit
• Avenin
• Ƴ-Zein
• ᵦ-Zein
• Rich S-rich
prolomin
Classification of proteins based on their solubility

7. 2S ALBUMIN STORAGE PROTEINS
• 2S Albumin defined on the basis of their sedimentation coefficients
(S20.w).
• One of the most widely distributed proteins in dicot seed about 25
albumin protein are present.
For Example: Oilseed rape belongs Family Cruciferae (in which that
protein present called Napins) and Arabidopsis.
• Napin proteins are well known in oil seed rape plants. The 25 albumin
and globulin storage proteins are widely distributed in flowering
plants, the alcohol soluble prolamins are restricted to grass family that
are present in major cereals.
• They are synthesized as single precursor proteins that are
proteolytically cleaved with the loss of a linker peptide and short
peptides from both the N and C termini.

9. GLOBULINS
• Globulin storage proteins are widely distributed in dicots as well as in
monocots.
• Found in embryo and outer aleurone layer of the endosperm
• Easily soluble in dilute salt solution
• Sedimentation coefficient about 7
• On the basis of their sedimentation coefficient divided into two groups,
like 7S Vicilin type, globulins and 11S Legumin type globulins.
• Much more variable in structure than the 7S and 11S globulins
• Storage globulins of 11S located in the starchy endosperm are also
present in atleast some cereal grains.

10. • The 11S globulins consist of six subunit pairs and each of these
subunit pairs consist of acidic subunit (MW 40,000) and basic unit
(MW 20,000) linked by a single disulfide bond. In contrast, 7S
globulins are trimeric proteins of 150,000 to 190,000 that lack
cysteine residue.
• They exhibit considerable nutritional significance in that they are
deficient in cysteine and methionine.
• Usually removed by milling (wheat), polishing (rice), pearling
(barley) or decortication (sorghum), before human consumption.

11. Hypothetic Pathway for the Evolution of
Germins and Globulin Storage Proteins

12. PROLAMINS
• Major endosperm storage proteins of all cereal grains (except rice and
oat).
For Example: Wheat, Barley, Rye, Maize, Sorghum, Millets etc.
• Rich in proline and amide nitrogen derived from glutamine
• Readily soluble in alcohol-water mixture solution (60-70% ethanol)
• Presence of amino-acid sequences consisting of repeated blocks on one
or more short peptide motifs (Methionine, Glycine, Histidine etc)
For Example: Zein
• Exception of rice, nearly half of the prolamins are further classified into
sulphur rich, sulphur poor and high molecular weight (HMW)
prolamin based on their amino acid sequence.

14. • The α-Zein account for 75 to 80% of the total proteins in maize and
are categorized into two groups: One is M 19,000 and second is
22,000.
• Both have similar structure, consisting of unique N and C-terminal
domains flanking sequences.
• Major source of Zein proteins are cereals.

15. GLUTELIN
• Soluble in dilute acids or bases
• Generally, prolamin like proteins in certain grass seeds
For Example: Wheat
• Most common glutelin, Glutenin found in wheat.
• It imparts baking quality to wheat
• Glutenin, a major storage protein in rice, originates from the same
ancestral gene as Leguminous 11S globulin irrespective of difference
in solubility.

16. Glutelin Structure

17. DECOMPOSITION OF SEED STORAGE
PROTEINS AT SEED GERMINATION STAGE
• SSPs provide nitrogen and sulphur source material for new protein
synthesis during seed germination
• Predominantly studied in seeds of cultivated plants (cereal grains and
legumes)
• SSPs broken down into soluble peptides by endopeptidase.
• Subsequently, these peptides are decomposed into smaller peptides or
amino acids by exopeptidase
• Peptidase is secreted from the cotyledons in dicot and from the
aleurone layer and scutellum in monocots after water absorption by the
seed
• This peptidase secretion is triggered by the plant harmone Gibberellin
(GA)
• Amino-acids produced from decomposition of SSPs are used as a
source for new protein synthesis during germination and subsequent
seedling growth.

18. TYPES OF SEED
Dicot Seed Monocot Seed

19. ENGINEERING PLANT SEED STORAGE
PROTEINS
• Present strategy in the modification of seed storage protein is mainly
focused on increasing concentration of sulphur containing amino acids
(S-rich amino acids) in legume seeds and lysine content in cereals.
• Cereal grains containing lysine rich protein consumed as high profile
energy source in the diet of humans and lives stock. Generally, Cereal
seeds are tend to be deficient in lysine, threonine and tryptophan.
• Legumes seed is the richest source for proteins (upto 40%) but shows,
deficient in methionine and cysteine content as well as tryptophan
(sulphur containing amino acid).
For Example: Pea seed protein containing around 0.8% methionine and
1.0% cysteine. This level is insufficient for growth and development.

20. CAUSES – ENGINEERING PLANT SEED
STORAGE PROTEINS
• Lives stock animals however, require 3.5% by weight of dietary protein.
• Besides, people who consumes only vegetarian food suffers health
problem due to amino acid imbalance.
• Therefore, breeding and genetic engineering methods can drive increase
in concentration of essential amino acid to overcome nutritional
imbalance.

21. Transgenic technology for tailoring the quality of
seed storage protein
Gene Crop Promoter Transgenic
plant
Improvemen
t
2S-rich Ƴ-
Zein
Maize CaMV35S
promoter
Alfa alfa S-content
2S protein Brazil nut CaMV35S
leg B4
Vicia
narborensis
Tobacco
Methionine
2S protein Sunflower CaMV35S Legumes Sulphur
content
ᵦ-phaseolin Common
bean
Rice glu
promoter
Rice Lysine
HS-7 Zein Maize 27kDa Zein
promoter
Rice Methionine
Ferritin Soyabean Rice glu-B1
promoter
Rice Fe-content

22. BREEDING STRATEGY
• Several pain staking breeding experiments have evolved a novel
approach in the improvement of amino acid profiles in the seeds of
several pulses and cereals.
• One of the earliest successes in breeding technique is the substantial
increase in the concentration of lysine amino acid content in maize
plant.
• Several mutation breeding experiments reveals that any increase in one
particular amino acid is always followed by declining amino acid
concentration.
• As a result of the above mutant work, the S-amino acid content of total
seed protein remains constant.

23. NOVEL APPLICATION OF SEED
STORAGE PROTEINS
• Especially crop seeds are used for the production of valuable proteins
or peptides.
• Transgenic seed has many benefits like bioreactor, due to high-level
expression of recombinant protein can be easily achieved.
• Engineered peptides can be produced and sequestered exclusively in
the seed without causing deleterious effects in other vegetative tissues,
when specifically expressed in seed.
• Moreover, recombinant proteins are stable in transgenic seed for
several years at room temperature.
• Possibly, transgenic seeds could easily provide bioactive function by
oral feeding without extraction of bioactive components.

24. • SSPs are useful for high accumulation of recombinant protein as
carrier protein.
• SSP-fused recombinant protein can be easily deposited in seed cells.
• SSP-fused recombinant protein (peptide) expressed under the
control of the SSP promoter provides an ideal combination as an
accumulation system for recombinant protein.
• Soybean glycinin, rice glutelin, and their promoters are actually
used for accumulation of bioactive peptides or epitopic peptides.
• Transgenic seed accumulating human health promoting proteins
may be practically used as bioactive foods in the future.

25. THANKYOU
A Biodiction (A Unit of Krishna Academy)