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V G SHOBHANA

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Title: V G SHOBHANA


1
BIOFORTIFICATION IN MAIZE
  • V G SHOBHANA
  • Dr. N SENTHIL
  • KALPANA K.
  • Dr. P NAGARAJAN
  • Dr. M RAVEENDRAN
  • Dr. P BALASUBRAMANIAN
  • CENTRE FOR PLANT MOLECULAR BIOLOGY
  • TAMIL NADU AGRICULTURAL UNIVERSITY
  • COIMBATORE 641 003

2
BIOFORTIFICATION
Fortification x Biofortification
  • Methods
  • Selective Breeding
  • Genetic modification
  • The Big Difference!!
  • Developing world
  • Vitamin A, Zinc, Iodine and Iron
  • Developed world
  • Selenium, prostrate cancer

The Orange Ribbon Symbol of Malnutrition
3
Importance
  • Two billion people - currently micronutrient
    malnourished - increased morbidity and mortality
    rates, lower worker productivity and high
    healthcare costs.
  • Nutritional deficiencies (iron, zinc, vitamin A)
    - almost two-thirds of the childhood death
    worldwide.
  • Major food crops can be enriched
    (biofortified) with micronutrients using plant
    breeding and transgenic strategies.
  • Micronutrient enrichment traits exist within
    their genomes.
  • Micronutrient element enrichment of seeds can
    increase crop yields when sowed to
    micronutrient-poor soils, assuring their adoption
    by farmers.

4
The Golden Rice Story
5
Percentage of population affected by
under-nutrition by country, according to United
Nations statistics
6
(No Transcript)
7
Phytic acid (Phytin or Phytate)
BIOSYNTHETIC PATHWAY
  • Myo-inositol-1,2,3,4,5,6-hexakisphosphate or Ins
    P6.
  • Is the most abundant myo-inositol phosphate in
    plant cells, but its biosynthesis is poorly
    understood.
  • Also uncertain is the role of myo-inositol as a
    precursor of phytic acid biosynthesis.
  • MW 660.03Formula C6H18O24P6

8
  • PHYTIC ACID
  • Myo-inositol 1,2,3,4,5,6-hexakisphosphate, is
    abundant component of plant seeds.
  • Deposited in protein bodies as a mixed salt of
    mineral cations such as K, Mg2, Ca2, Zn2,
    and Fe 3 (50 to 80 of the phosphorus in
    seeds).
  • Phytic acid serves as a major storage form for
    myo-inositol, phosphorus, and mineral cations for
    use during seedling growth.
  • Other known role of phytic acid - control of
    inorganic phosphate (Pi) levels in both
    developing seeds and seedlings.
  • In maize kernels, nearly 90 is accumulated in
    embryo and 10 in aleurone layers (also in rice
    and barley).
  • Maize endosperm contains only trace amount of
    phytic acid.

9
Importance
  • Monogastric animals digest phytic acid poorly.
  • Undigested phytic acid is eliminated and is a
    leading phosphorus pollution source.
  • Low-phytic acid grain and legume in feed -
    reduces phosphorus pollution to environment and
    reduce amount of phosphorus supplementation
    required in animal feeds (Ertl et al., 1998).
  • Such grain would also offer more available Fe and
    Zn for human nutrition (Mendoza et al., 1998).

10
Variability of phytate P in crop plants
11
Biosynthetic pathways of phytate in plants
  • Two types of pathway
  • Lipid -dependent (hydrolysis of PI(4,5)P2 by
    phospholipase)
  • Lipid -independent (sequential
    phosphorylation of I(3)P or inositol)

Paulik et al.,(2005)
12
Analysis of biochemical characters
  • Phytic acid Wheeler and Ferrel, 1971
  • 430 genotypes were screened for their phytate
    content
  • Low and high maize inbreds were identified
  • Crossing of low inbred with high inbreds evolved
    in 50 hybrids
  • Iron and Zinc major minerals screened by
    Atomic Absorption Spectrophotometer

13
The following strategies were adopted to reduce
the phytate
  • Plants can be transformed for increased phytase
    production in the seeds.
  • The transgenic approach will, in the long run,
    prove to be most versatile and cost-effective.
  • Mutation breeding for impaired phytic acid
    biosynthesis has proved to be useful in maize,
    barley and rice ( Raboy, 2000).
  • Available low phytate mutant lines can be crossed
    with locally adopted cultivars and will result in
    low phytate maize with desired agronomic
    backgrounds.

14
Genetics
  • Maize has 10 chromosomes (n10).
  • The combined length of the chromosomes is 1500
    cM.
  • "Chromosomal knobs". They are highly repetitive
    heterochromatic domains that stain darkly.
  • Barbara McClintock used these knob markers to
    prove her transposon theory of "jumping genes".

Composition Figures in grams (g) or milligrams
(mg) per 100g of food.
Minerals Calcium 9mg Phosphorus 290mg Iron 2.5m
g
Seed (Fresh weight) 361 Calories per 100g
Water 10.6 Protein 9.4g Fat 4.3g Carbohydrate
 74.4g Fiber 1.8g Ash 1.3g
Vitamins Vit A 140mg Thiamine
(B1) 0.43mg Riboflavin (B2) 0.1mg Niacin 1.9mg
15
Mutation work - Dr. V Raboy, USDA
  • Pollen treated M2 progenies - developed by Dr.
    Raboy yielded two maize mutants.
  • lpa 1 and lpa 2 with 60 reduction in the seed
    phytate levels were produced.
  • These mutants were widely used in most of the
    breeding programmes in US.
  • lpa 1 1.1 (mg/g) phytate P in 4.7 (mg/g) total
    P
  • lpa 1 2.6 (mg/g) phytate P in 4.6 (mg/g) total
    P
  • Indian corns have 2.0 2.5 (mg/g) phytate P in
    4.0 - 4.5 (mg/g) of total P.

16
INBREDS SELECTED FOR MUTATION BASED ON PHYTIC
ACID CONTENT
17
INBREDS SELECTED FOR MUTATION BASED ON THE PHYTIC
ACID CONTENT
18
Methodology
  • Low phytic acid donors with lpa1 and lpa2 genes
    will be used from Victor Raboy, USDA and will be
    used to develop low phytate maize.
  • Local inbred lines will be used as recurrent
    parents.
  • Identification of closely linked DNA markers with
    phytate in maize using already available linked
    markers like umc157 with lpa1 and umc167 with
    lpa2.
  • Develop backcross population and marker assisted
    backcross selection for low phytate maize lines.

19
Expected output
  • Identification of low phytate genotypes of maize
    which could be potential donors in breeding for
    micronutrients.
  • Molecular markers linked to low phytate will
    assist in identifying target genes involved in
    adsorption, transport and unloading of
    micronutrients in the grain.
  • Low phytate versions of high yielding maize
    hybrids in cultivation in India with increased
    iron and zinc bioavailability and reduced
    phosphorus pollution in the environment.
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