Cellular signal transduction pathways under abiotic stress


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Abiotic stresses, especially cold, salinity and drought, are the primary causes of crop loss worldwide. Plant adaptation to environmental stresses is dependent upon the activation of cascades of molecular networks involved in stress perception, signal transduction, and the expression of specific stress-related genes and metabolites. Plants have stress-specific adaptive responses as well as responses which protect the plants from more than one environmental stress. There are multiple stress perception and signaling pathways, some of which are specific, but others may cross-talk at various steps (Knight & knight ,2001).Many cold induced pathways are activated to protect plants from deleterious effects of cold stress, but till date, most studied pathway is ICE-CBF-COR signaling pathway (Miura and Furumoto,2013 ) . The Salt-Overly-Sensitive (SOS) pathway, identified through isolation and study of the sos1, sos2, and sos3 mutants, is essential for maintaining favorable ion ratios in the cytoplasm and for tolerance of salt stress (shi .et al ,2002). Both ABA-dependent and -independent signaling pathways appear to be involved in osmotic stress tolerance (Nakashima and shinozaki, 2013) .ROS play a dual role in the response of plants to abiotic stresses functioning as toxic by-products of stress metabolism, as well as important signal transduction molecules and the ROS signaling networks can control growth, development, and stress response ( Mahajan,s and Tuteja, 2005) .

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Cellular signal transduction pathways under abiotic stress

  1. 1. Drought salt Heat Cold Cellular Signal Transduction Pathways under abiotic stress in plants & its applications Chavan Neha
  2. 2. Securing food with less land 13 billion hectares (Earth’s surface) 1.5 billion 3.5 billion hectares ( agriculture) (meadowland pasture.) seven million hectares of agricultural land are lost (every year) Need of four billion hectares of land. As a result of population growth, agricultural production must increase by around two percent per year . (FAO statistical division ,2008)
  3. 3. What is stress??? ‘’A biological stress is an adverse force or a condition, which inhibits the normal functioning and well being of a biological system such as plants .’’ (jones et.al ,1989)
  4. 4. Stress elicitors • cell response is initiated by interation of extracellular material with plasma membrane protein. • The extracellular molecule is called as ligand and the protein with which it will interact is called as receptor. Abiotic 1. Cold (chilling and frost) 2. Heat (high temperature) 3. Salinity (salt) 4. Drought (water deWcit condition) 5. Excess water (Xooding) 6. Radiations (high intensity of ultra- violet and visible light) 7. Chemicals and pollutants (heavy metals, pesticides, and aerosols) 8. Oxidative stress (reactive oxygen species, ozone) 9. Wind (sand and dust particles in wind) 10. Nutrient deprivation in soil Biotic 1. Pathogens (viruses, bacteria, and fungi) 2. Insects 3. Herbivores 4. Rodents (Mahajan & Tuteja, 2005)
  5. 5. Major cause of loss in Crop production stress •Stress reduces harvests dramatically •Abiotic factors are responsible for the lion’s share of harvest losses, however. (Bayers crop science magazine,2008)
  6. 6. How abiotic stress affects the growth and development of crop (Vicers et.al ,2009)
  7. 7. Biotechnological approches to study stress response in plants (Climente et.al,2013)
  8. 8. Overview of signal transduction pathway (Mahajan & Tuteja, 2005)
  9. 9. Crosstalk of signal transduction pathways (Knight & knight ,2001)
  10. 10. Complexity (Wangxia Wang et al.,2003)
  11. 11. Types of signal transduction pathways Ionic &Osmotic stress signaling Signaling to co- ordinate cell division & expansion Signaling for detoxification . (Jian –kang Zhu ,2011) Cellular Homeostatis Control and repair cell damage due to stress To level suitable stress condition
  12. 12. (Miransari et al ,2013) Contd..,
  13. 13. Major signal transduction pathways under abiotic stress(drought ,salt and osmotic stress ) • ABA (dependent and independent)signaling • MAPK mediated signaling • SOS signaling • Phospholipid signaling.
  14. 14. ABA biosynthesis (Zhu et al ,2005) Pyrophosphate +glyceraldehyde 3 phosphate IPP(isopentenyl pyrophosphate) Farnesyl pyrophosphate,GGPP,B-carotein Beta carotein Zeaxanthin ZEP Violaxanthin NCED Neoxanthin Xanthoxin ABA aldehyde Xanthoxinic acidABA Phaseic acid Abscisic alcohol
  15. 15. ABA conjugation • ABA can be inactivated at C1 ,by forming different conjugate . • One of this conjugate is ABA –GE • Over-expression of UGT71B6 leads to an increased ABA-GE content in Arabidopsis. The incresed ABA-GE will be stored in vacuoles. • What happens is that under dehydration condition the GE gets separated out from ABA by the enzyme Betaglucosidase(BG) ‘’Recently 2 BG ,BG1 and BG2 identified in Arabidopsis’’ (Danquah et al , 2013) Free ABA
  16. 16. ABA Transport : Two main transporters of ABA – 1.AtABCG25 2.AtABCG40 ‘’ The stomata of atabcg40mutants close more slowly in response to ABA, resulting in reduced drought tolerance.’’ (Danquah et al , 2013)
  17. 17. Early events in ABA signaling (Nakashima & shinozaki ,2013) Identification of SnRK2
  18. 18. ABA dependent and Independent pathway
  19. 19. Mitogen activated protein kinase pathway (Danquah et al , 2013)
  20. 20. Recent updates • ZmMkk1-Chilling stress & pathogen defence (Cai et al ,2013 ) • ZmMkk3- mediates osmotic stress and gives signal for ABA (Cai et al ,2013 ) • ZmMpk5-salt stress in maize (Zang et al ,2013) • MAPK3 – confers U.V and Heat tolerance (Raina et al ,2013 )
  21. 21. (Danquah et al , 2013) ABA induced activation of MAPK ABA perception in guard cell activate SnRK2 kinase (OST 1) Phosphoraylation of NADPH oxidase Rhof Leads to ROS accumilation Activate 2 MAPKs,MPK9/12 SLAC activation Stomal opening SLAC-s type ionic channel PYR- Enhanced transpiartional loss
  22. 22. SOS pathway under salt stress (Mahajan & Tuteja ,2005)
  23. 23. Osmotic stress, cold, and ABA activate several types of phospholipases that cleave phospholipids to generate lipid messengers (e.g., PA, DAG, and IP3), which regulate stress tolerance partly through modulation of gene expression. FRY1 (a 1-phosphatase) and 5- phosphatase-mediated IP3 degradation attenuates the stress gene regulation by helping to control cellular IP3 levels. Phospholipid signaling (jian-kang Zhu ,2002)
  24. 24. PLD and PA in response to H2O2 PLD , is activated in response to H2O2 and the resulting PA functions in amplification of H2O2 -promoting antiPCD Stress stimulates production of H2O2 that activates PLD associated with the plasma membrane. Potential activators: Ca2+ and oleic acid. This increases PLD affinity to its substrates, stimulating lipid hydrolysis and PA production. PA may bind to target proteins, such as Raf-like MAPKK, that contain a PA binding moti, leading to the .) activation of MAPK cascades. PA may also function by modulating membrane trafficking and remodeling. These interactions modulate the cell's ability to respond to oxidative stress and decrease cell death. Dashed lines - hypothetical interactions.
  25. 25. •Knockout of PLD renders Arabidopsis plants more sensitive to the reactive oxygen species H2O2 and to stresses •H2O2 activates PLD , and PLD -derived PA functions to decrease the promotion of cell death by H2O2. These results suggest that both PLD and its product PA play a positive role in signaling stress responses •PLD and its derivative PA provide a link between phospholipid signaling and H2O2-promoted cell death. PLD and PA positively regulate plant cell survival and stress responses. PLD and PA (Laxalt and Munnik,2002)
  26. 26. Transcriptional regulatory network under abiotic stress responses (Hirayama & shinozaki ,2010)
  27. 27. Signaling under heat stress (Bokszczanin & fragcostefanakis ,2013)
  28. 28. Signaling under cold stress Cold stress signaling with secondary messenger Plants may sense low temperature through changes in the physical properties of membranes, because membrane fluidity is reduced during cold stress plasma membrane rigidification raised by a membrane rigidifier, dimethyl sulfoxide (DMSO), Induction of COR gene Second shock Increase in ca+ Regulation of COR gene expression Ca sensors CBF calmodulin CDPKs CCaSK Positive regulation of cold stress Negative regulation of cold stresss CAMAT Miura and Furumoto,2013
  29. 29. CBF dependent signaling Miura and Furumoto,2013 ICE1
  30. 30. Applications
  31. 31. Case study 1
  32. 32. Experimental protocol and results 1.Overexperssion of SOS1 in transgenic plants: A. A.thaliana plants were transformed with a construct containing the SOS1 cDNA driven by the cauliflower mosaic virus (CaMV) 35S promoter. B. Screening is done on M.S. agar medium cantaining 40mh/l kanamycin. C. Presence confirmed by PCR (primer specific for 35s promoter and SOS1gene ) 2.RNA gel Blot: A. A.Thaliana plant grown on M.S.medium under continous light. B. For salt treatment 10 days old seeding Whatman filter paper soaked with 100mM Nacl &200 mM Nacl Whatman filter paper soaked in M.S. medium (stress) (Control) Total RNA isolation and Nouthern analysis
  33. 33. Control transgenic Stress given 0mM,1oomM,200mM Resisitant lines (ST-4,ST-8) analysised for RNA gel Blot
  34. 34. Same lines S-4 ,S-8 grown on medium (M.S),cantaning different conc. of Nacl Physiological analysis of plants Root growth Chlorophyll content Total protein level
  35. 35. figure 4. :Reduced Na+ accumulation in plants overexpressing SOS1. control ST -8 ST-4
  36. 36. Figure 3. Enchanced salt tolerance of SOS1-overexpressing plants Control 50 mM 150mM
  37. 37. Figure 5. Calli overexpressing SOS1 are more tolerant of NaCl.
  38. 38. Case study 2
  39. 39. Results High expresssion was found in P58 and P1142
  40. 40. Fig. 2 Growth characteristics of the AtDREB1A plants and the cultivar BR16 under control (C-dark bars) and moderate water stress (DS-grey bars) conditions in the greenhouse. Differences were not statistically significant (Duncan 5 %) (n = 6)
  41. 41. Transpiration of Atderb1A plants an cultivator BR16 ,A - water stress ,B-in greenhouse Green house phytotron
  42. 42. Conclusion • Abiotic stress signaling is an important area with respect to increase in plant productivity. Therefore, the basic understanding of the mechanisms underlying the functioning of stress genes is important for the development of transgenic plants. Each stress is a multigenic trait and therefore their manipulation may result in alteration of a large number of genes as well as their products. A deeper understanding of the transcription factors regulating these genes, the products of the major stress responsive genes and cross talk between different signaling components should remain an area of intense research activity in future.
  43. 43. Discussion
  44. 44. References • Knight,H.and knight,M.R.2001.Abiotic stress signaling pathways:specificity and crosstalk.Trends in Plant sci.,6:262-267 • Zhu,J.K.2002.Salt and Drought stress signal transduction in plants.Ann.Rev.Plant Biology,53:247-273. • Danguah,A.,Zelicourt,A.,colcombet,J.and Hirt,H.2013.The role of ABA and MAPK signaling pathways in Plant abiotic stress response.Biotechnological Adv., • Hirayama,T and Shinozaki,k.2010.Research on Plant abiotic stress response in post genome era:past,present& future.The Plant journal,61:1041-1052 • Mahajan,s and Tuteja,N.2005.cold,salinity & drought stress:An overview .Archi.Biochem.biophysics,444:139-158
  45. 45. References • Miura,k and Furumoto,T.2013. Cold Signaling and Cold Response in Plants.Int.J.Mol.Sci.,14:5313-5337. • Shinha,A.k.,Jaggi,M.,Raghuram,B.and Tuteja,N.2011.Mitogen activated protein kinase signaling in plants under abiotic stress.Plant signaling and behaviour,6:196-203 • Nakashima,K.and shinozaki,K.Y.2013.ABA signaling in stress response & seed development.Plant cell Rep,32:959-970 • Shi,H.,Lee,B.Wu,S.and Zhu,J.2002.Overexpression of plasma membrane Na+/H+ antipoeter gene improves salt tolerance in arabidopsis .Nature Biotechnology,21 • Bokszczanin ,K.L., and Fragkostefanakis ,S.2013.Perspectives on deciphering mechanisms underlying plant heat stress response and thermotolerance.Frontiers in Plant Sci.,4:135
  46. 46. Thank you…..