1) The document discusses molecular responses of plants to abiotic stresses such as drought, salinity, temperature, and toxicity. It covers stress signaling pathways, gene expression under stress conditions, and case studies on crops like wheat, tobacco, rice, and cotton. 2) Key responses discussed include activation of signaling molecules like ABA, MAPK, and ROS, induction of transcription factors, altered gene expression including for osmolytes like proline, and stress avoidance or tolerance mechanisms. 3) Case studies examined the roles of genes like WRKY, LEA3-2, in conferring drought and salt tolerance and identified stress-regulated genes and cross-talk networks between different stresses.

1. Welcome
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2. Molecular response of plants to
Abiotic Stresses
A.DINESH
Jr. M.Sc(Agri)
PG13AGR5055
Dept: Genetics and plant breeding
Seminar-I
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3. Content
INTRODUCITON
TERMINOLOGIES
SIGNALING PATHWAYS
GENE EXPRESSION TO STRESS CONDITION
PROLINE SYNTHESIS
CASE STUDIES
CONCLUSIONS
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4. Losses caused by the Abiotic stress
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• 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)

5. STRESS
ABIOTIC
WATER
DEFICIT
TEMPERATURE
EXCESS
HIGH
LOW
TOXICITY
SALT/ION
DIFFICIENCY
AIR
POLLUTION
OTHERS
BIOTIC
Plant stress
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6. Heat stress
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7. 7

8. Water depletion :
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9. Water stress :
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10. Lobell et al., 2011
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11. Terminology:
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• 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

12. Cramer et al., 2011
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13. How plants respond to environmental
stress ?
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14. Stress resistance mechanisms
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1. Avoidance mechanisms
⚫preventsexposure tostress
2. Tolerance mechanisms
⚫permit the plant towithstand stress
3. Acclimation
⚫alter theirphysiology in responsestress

15. Plants molecular mechanisms in
response to stress involve:
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⚫Activation of signaling pathways
⚫Production of ROS
⚫Activation of transcription factors
⚫Alter gene expression
⚫Breakdown of macro molecules
⚫Decrease in protein synthesis
⚫Synthesis of osmolytes

16. General Stress Signal Transduction
Pathway
(Xiong and Zhu, 2001)
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17. Abscisic acid (ABA) synthesis :
1.Zeaxanthin epoxidase (ZEP
,)
2. 9-cis-epoxycarotenoid
dioxygenase (NCED).
3.ABA-aldehyde oxidase(AAO)
4.Molybdenum
cofactor sulfurase (MCSU)
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18. ABA Signal transduction :
Danquah et al., 2013
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19. Stomatal closure under stress :
Qin et al., 2011 19

20. Mitogen Activated Protein Kinase
(MAPK) :
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Danquah et al., 2013
Fig. 2. A typical MAPK cascade.

21. ROS production
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22. Oxidative stress
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23. ROS signal transduction
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Fig. 1.Three stages are proposed to exist in this signal transduction
Miller et al., 2008

24. Cold stress :
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Qin et al., 2011

25. Osmotic stress
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26. Gene expression to osmotic stress :
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27. 27
Shinozak et al.,1997

28. Heat stress
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Hasanuzzaman et al., 2013

29. Genes linked to more than one abiotic stresses
Ahuja et al., 2010
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30. Osmolyte : Proline
Szabados and Savoure, 2009
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31. Functions of Proline :
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32. Glycinebetine:
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33. 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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40. Daun and Cai, 2012 40
Plant materials and methods :
Rice cultivar ZH11 used in transformation, Arabidopsis thaliana
Vectors : pYES2, pHB
Objective :
To identify the role of osLEA3-2 in salt and drought tolerance

41. 41

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43. 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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47. Method and Treatments :
Upland cotton (Gossypium hirsutum L.) C312
1. ABA
2. Salinity stress : NaCl
3. Cold : 4°C
4. Drought stress : Mannitol.
5. Alkalinity stress : pH 11,
Objectives:
1. Transcriptome profiling of cotton seedlings stressed with
ABA, cold, drought, salinity and alkalinity .
2. Differentially expressed genes and related crosstalk
network for stress perception, signal transduction
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Zhu et al., 2013

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50. 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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53. Yamamoto and Momonoki, 2012
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Objective :
1. Role of acetylcholinesterase enzyme (AChE) to
heat stress
2. Tissue localization of maize acetylcholinesterase
enzyme.

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