Transcript Transgenic Approach for Abiotic Stress Tolerance

Transgenic Approach for
Abiotic Stress Tolerance
No.
Characteristics features of
plant stress protein
Stress Protein
Induction agent
Characteristics features
1
HSP (heat shock Mostly by high
protein)
temperature stress,
also by water stress,
salt stress, low
temperature stress,
in some cases also
by abscisic acid
Classified aslow molecular weight HSPs
and high molecular weight HSPs, highly
conserved amino acid sequence,
nucleotide sequence of the
corresponding genes is also conserved,
stress-inducible of hs genes governed by
HSEs (heat shock elements), selected
HSPs are shown to act as chaperons
2
Osmotic stress
proteins such as
WSPs (water
stress proteins)
and SSPs (salt
stress proteins)
Varied molecular weights and cellular
locations, these proteins are mostly the
enzymes involved in diverse functions
such as production of different
osmolytes, protein degradation, signal
transduction events, gene regulation and
transport. Roles of some WSPs is not well
defined (i.e. such as for dehydrins, late
embryogenesis, abundant proteins)
Mostly by low water
availability and salt
stress, also induced
by ABA
Characteristics features of
plant stress protein
No. Stress Protein Induction agent
Characteristics features
3
ANPs
(anaerobic
proteins)
Mostly by
anaerobic stress
(caused by
flooding or
submergence
stress)
Discovered initially in maize and
later shown tin o be universally
present, most of the ANPs have been
shown to be the enzymes of the
fermentative or the glycolytic
pathway, most genes encoding ANPs
contain . AREs (anaerobic response
elements) in their promoters
4
Cold stress
proteins such
as COR (coldregulated
proteins)
Mostly by low
temperature
stress, also by
osmotic, oxidative
stress and ABA
Conserved proteins of varied sizes
and functions, most COR genes
contain specific nucleotide sequence
that stimulate transcription in
response to low temperature
Stress Induced gene
expression
1.Genes encoding proteins with known
enzymatic or structural functions
2.Protein with as yet unknown functions
3.Regulatory protein
Single action gene
Osmoprotectant genes: Proline, Gly/Bet, Sugar polyols
Detoxifying genes: SOD, PX
Late embryogenesis abundant genes: LEA
Transporter genes: Aquapurin, Ion transporter
Multifunctional genes for lipid biosynthesis:GPAT
(glycerol-3-phosphate acyltransferase), FAD7 (Fatty acid
desaturase)
Heat shock genes: HS
Regulatory Genes
Transcription factors genes
CBF/DREB, ABF, HSF, bZIP, MYC/MYB
Signal transduction genes
a. Osmocensors (AtHK-1)
b. Phospholipid cleaving enzymes (PLD)
c. Second messengers (Ptd-OH, ROS)
d. MAP kinases, Ca+ censor (SOS-3)
e. Calcium –dependent protein kinases (CDPKs)
Abiotic stress tolerance
1.Increase cellular level of osmotically-active
solute (proline, glycinebetaine, mannitol,
trehalose, fructans)
2.Increase levels of osmolytes
3.It is mediated by a number of biochemical
reactions /physiological processes (a multi genic
trait)
4.It can be augmented by pyramiding different
stress-responsive genes
Osmolyte and Compatible
Solutes
Gene
gpat
Protein
Glycerol 3phosphate
acyltransferase
Source
Cucurbita
maxima,
Arabidopsis
thaliana
Cellular role(s)
Fatty acid
unsaturation
mtlD
Mannitol 1phosphate
dehydrogenase
Superoxide
dismutase
Betaine
aldehyde
dehydrogenase
Eschericia coli
Manitol
biosynthesis
Nicotiana
plumbaginifolia
Eschericia coli
Superoxide
dismutase
Glycinebetaine
dismutase
sod
Bet-B
Osmolyte and Compatible
Solutes
Gene
Bet-A
Sac-B
Protein
Choline
dehydrogenase
Pyroline 5carboxylase
synthase
Levan sucrase
Hva-1
LEA protein
Tps-1
Trehalose 6phosphate
synthase
p5cs
Source
Eschericia coli
V. aconitifolia
Cellular role(s)
Glycinebetaine
dismutase
Proline
biosynthesis
Baccilus subtilis Fructan
biosynthesis
Hordeum
vulgare
Arabidopsis
Trehalose
thaliana
biosynthesis
Osmolyte and Compatible
Solutes
Gene
Protein
Cod-A/Cod-1/Cox Choline oxidase
afp
Source
Arthrobacter
globiformis
Antifreeze protein Synthetic
(AFP)
Imt-1
Myo-inositol-omethyl
transferase
BADH
Betaine
dehydrogenase
Cellular role(s)
Glycinebetaine
biosynthesis
Inhibit ice growth
and
recrystallization
Messembryanthe D-ononitol
mum crystallinum biosynthesis
Spinach
Glycinebetaine
byosynthesis
Osmolyte and Compatible
Solutes
Gene
Ect-A, Ect-B,
Ect-C
Ots-A, Ots-B
Protein
L-2,4diaminobutyric
acetyltransferase
L-2,4diaminobutyric acid
trans-aminase
L-ectoine synthase
Trehalose-6-P
synthase
Trehalose-6-P
phosphatase
Source
Halomonas
elongata
Cellular role(s)
Ectoyne
Eschericia coli
Trehalose
Osmolyte and Compatible
Solutes
Gene
Pro-DH
HAL-3
Protein
Source
Cellular
role(s)
Proline
Arabidopsi Proline
dehydrogena s thaliana
se
FMN-binding Saccharo Na+/K+
protein
myces
homeostas
cerevisae is
Ion Transporters and Ion
Homeostasis
Gene
Protein
Source
AtNHX-1
Vacuolar Na+/H+
antiporter
Plasma
membrane
Na+/H+ antiporter
Vacuolar H+pyrophosphatase
K+/Na+ transport
regulation
Arabidopsis
thaliana
Arabidopsis
thaliana
AtSOS-1
AVP-1
HAL-1
Arabidopsis
thaliana
Saccharomyc
es cerevisiae
Cellular
role(s)
Na+ vacuolar
sequestration
Na+ extrusion
Vacuolar
acidification
K+/Na+
homeostasis
Redox Proteins
Gene
MnSOD
Gly-1
Protein
Superoxide
dismutase
Glyoxylase
Source
Saccharomyces
cerevisiae
Brassica juncea
TPX-2
Peroxidase
GST
Glutathione Stransferase
Glutathione
peroxidase
Nicotiana
tabacum
Nicotiana
tabacum
Nicotiana
tabacum
GPX
Cellular role(s)
Reduction of O2
content
S-Dlactoylglutathion
e
Change cell
properties
ROS
scavenging
Transcription and signal
transduction factors
Gene
Protein
DREB-1A
Transcription
factor
Cnb-1
Calcineurin
OsCDPK-7
Protein kinase
Source
Cellular
role(s)
Arabidopsis Improved
thaliana
gene
expression
Saccharomyc Improved
es cerevisiae Ca++
signaling
Oryza sativa Improved
gene
expression
Mischelineous
Gene
DnaK
Apo-Inv
Protein
Source
Cellular
role(s)
Heat shock
A.
Protein
protein
halophytica stabilization
Apoplastic yeast- Saccharomyc Sucrose
derived invertase es cerevisiae synthesis
Perspective in Abiotic Stress
Tolerance
1. Abiotic stress elicit multigenic responses within the plant cells. The
tolerance to different abiotic stress is contributed by a range of different
biochemical/physiological mechanism
2. Only a limited number of plant genes with a definite function have
been identified, cloned and characterized
3. Changing levels of transcription factors can alter the levels of several
genes at the same time
4. The transgenics raised far for enhancing tolerance to abiotic stress
have been achieved through employing strong constitutive promoters,
for driving expression of the transgenes. Promoters which are induced
by different abiotic stress including high temperature stress, anaerobic
stress, salt stress and water stress have poor strength of expression
when compared to constitutively expression promoter