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Welcome

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Molecular response of plants to Abiotic Stresses

A.DINESHJr. M.Sc(Agri) PG13AGR5055

Dept: Genetics and plant breeding

Seminar-I

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Content INTRODUCITON

TERMINOLOGIES

SIGNALING PATHWAYS

GENE EXPRESSION TO STRESS CONDITION

PROLINE SYNTHESIS

CASE STUDIES

CONCLUSIONS

Losses caused by the Abiotic stress

• The progressive salinization of soil, estimated at around 20 % of irrigated land in world (Ghassemi et al.,1995)

• High temperature coupled with drought during pollination period of maize plants can result in up to 100 % yield loss

(Heiniger et al., 2001)• It was estimated that approximately 70 % of yield reduction

was due to abiotic stress ( Acquaah, 2007)

• The estimated potential yield losses are 17 % due to drought, 20 % due to salinity, 40 % due to high temperature, 15 % due to low temperature and 8 % due to other stress

( Ashraf et al., 2008)

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STRESS

ABIOTIC

WATER

DEFICIT

EXCESS

TEMPERATURE

HIGH

LOW

SALT/ION

TOXICITY

DIFFICIENCYAIR

POLLUTION

OTHERS

BIOTIC

Plant stress

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Heat stress

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Water depletion :

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Water stress :

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Lobell et al., 2011

Terminology:• Heat stress : A transient elevation in temperature, usually 10-

15°C above ambient, is considered heat shock or heat stress (Wahid et al.,

2007) • Low-temperature stress : Chilling (<20°C) or freezing (<0°C)

temperatures can induce ice formation in plant tissues, leading to cellular dehydration (chinnusamy et al., 2007)

• Water stress: The condition where a plant’s water potential and turgor are decreased enough to inhibit normal plant function (Hsiao et al., 1973)

• Oxidative stress : It is an imbalance between the production of ROS and their scavenging 11

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Cramer et al., 2011

How plants respond to environmental stress ?

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Stress resistance mechanisms 1. Avoidance mechanisms

prevents exposure to stress2. Tolerance mechanisms

permit the plant to withstand stress3. Acclimation

alter their physiology in response stress

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Plants molecular mechanisms in response to stress involve:

Activation of signaling pathwaysProduction of ROSActivation of transcription factorsAlter gene expressionBreakdown of macro moleculesDecrease in protein synthesisSynthesis of osmolytes

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General Stress Signal Transduction Pathway

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Abscisic acid (ABA) synthesis :

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1.Zeaxanthin epoxidase (ZEP,)2. 9-cis-epoxycarotenoid dioxygenase (NCED).3.ABA-aldehyde oxidase (AAO)4.Molybdenum cofactor sulfurase (MCSU)

ABA Signal transduction :

18Danquah et al., 2013

Stomatal closure under stress :

19Qin et al., 2011

Mitogen Activated Protein Kinase (MAPK) :

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Danquah et al., 2013Fig. 2. A typical MAPK cascade.

ROS production

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Oxidative stress

ROS signal transduction

23Fig. 1.Three stages are proposed to exist in this signal transduction

Miller et al., 2008

Cold stress :

24Qin et al., 2011

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Osmotic stress

Gene expression to osmotic stress :

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27Shinozak et al.,1997

Heat stress

28Hasanuzzaman et al., 2013

Genes linked to more than one abiotic stresses

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Ahuja et al., 2010

Osmolyte : Proline

30Szabados and Savoure, 2009

Functions of Proline :

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Glycinebetine:

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Materials and Method : Wheat , Tobacco• PEG6000• NaCl solutions• H2O2• Total RNA : TRIzol reagent • Objective : To know whether WRKYs confer drought

and salt stress tolerance

Wang et al., 2013

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40Daun and Cai, 2012

Plant materials and methods :Rice cultivar ZH11 used in transformation, Arabidopsis thalianaVectors : pYES2, pHB

Objective : To identify the role of osLEA3-2 in salt and drought tolerance

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Figure 4. Growth of S. cerevisiae cells expressing OsLEA3-2 and the control cell in the medium containing 1.2 M NaCl (A), 1.2 M KCl,(B), and 2.0 M sorbitol (C).

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Method and Treatments : Upland cotton (Gossypium hirsutum L.) C312 1. ABA 2. Salinity stress : NaCl3. Cold : 4°C4. Drought stress : Mannitol.5. Alkalinity stress : pH 11,Objectives: 6. Transcriptome profiling of cotton seedlings stressed with ABA, cold,

drought, salinity and alkalinity . 7. Differentially expressed genes and related crosstalk network for

stress perception, signal transduction

Zhu et al., 2013

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Cross talk among stress genes

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Among the 64 induced and 62 repressed genes. Only 29 induced and 30 repressed genes have characterized in cotton and shown homology with Rice

13 of 29 commonly induced and 11 from the 30 commonly repressed transcripts took roles in signal transduction and regulation of gene expression under abiotic stresses

ABA signal transduction components, PP2C 77 and PP2C 12, were up-regulated

The genes DELLA protein RGA,4-coumarate--CoA ligase-like 7 and putative 12-oxophytodienoate reductase and HSP20, HSP70 were repressed

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Yamamoto and Momonoki, 2012

Objective : 1. Role of acetylcholinesterase enzyme (AChE) to

heat stress2. Tissue localization of maize acetylcholinesterase

enzyme.

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Thank you…..