This document discusses molecular basis and regulation of homeostasis in plants. It begins with a brief history of homeostasis and provides definitions. It then outlines the main topics to be covered, including hypotheses, mechanisms, physiological, biochemical and genetic regulation of homeostasis, case studies, and conclusions. The main points are that homeostasis involves maintaining a stable internal environment through negative feedback mechanisms. It is regulated at the physiological level through adaptations, at the biochemical level through transport systems and redox regulation, and at the genetic level through microRNAs and growth genes. Case studies examine salinity tolerance and malate metabolism. The conclusion restates that homeostasis maintains nutrient and ion balance internally through various mechanisms.

1. Molecular Basis and Regulation
of Homeostasis in Plants
Shivendra Kumar
L-2016-A-175-M
School of Agricultural Biotechnology
Punjab Agricultural University
Ludhiana

2. Organization
• History of homeostasis
• Definition of homeostasis
• Hypotheses of homeostasis
• Mechanism of homeostasis
• Regulation of homeostasis
o Physiological base
o Biochemical base
o Genetic base
• Case studies
• Conclusions

3. History of homeostasis
C. Bernard (1865) Walter Bradford Cannon (1926)
Concept of regulation of
internal environment
Coined the word
Homeostasis

4. Definition of Homeostasis
The maintenance of a relatively stable internal environment by an
organism in the face of a changing external environment and
varying internal activity using negative feedback mechanisms to
minimize an error signal
+=
How does a cell maintain homeostasis?

5. Hypotheses of homeostasis
Homeostasis and resorption of green-leaf N decreased
from vegetative to reproductive stages
Sleep and synaptic homeostasis: (animal system)
Stoichiometric homeostasis : (plant system)

6. S.No Nutrient Vegetative stage Flowering stage Grain filling stage
1 Nitrogen Higher Lower Higher
2 Phosphorous Lower Higher Lower
3 N:P Lower Higher Lower
doi: 10.1242/dev.086363

7. Effector
Regulated variable
Control center
Set point
Sensor
Mechanism of homeostasis in plants

8. External disturbance
Model H et al 2015 Plant Physiol 39: 259–266
Do Homeostatic
mechanisms operate
like an on/off switch?
Does Homeostasis
are worked on
feedback
mechanism?

9. Molecular mechanism involves maintaining of ionic balance inside the cell
Kehr J 2013 Front Pl Sci 4: 145. doi: 10.3389/fpls.2013.00145

10. Comparison of homeostasis
Sweating
Shivering
Maintaining
ions + H2O
Level of RBC
balance
Cutinization
Transpiration
http://www.ool.co.uk/i
gcse/human -biology/
www.ontrack-
media.net/gateway/biology

11. A. Physiological basis
B. Biochemical basis
C. Genetic basis
Regulation of homeostasis

12. Temperature based Adaptations based
C3 plant
C4 plant
CAM plant
Mesophytic plant
Hydrophytic plant
Xerophytic plant
A. Physiological basis

13. In C3 plants
Photosynthetic base of regulation
https://www.dreamstime.com/royalty-free-stock-photo-wheat

14. In C4 plants
https://upload.wikimedia.org/wikipedia/common
s/1/1a/maize

15. In CAM plants
Drought adaptation with CAM involves the use
of different storage carbohydrate pools
Ceusters J 2009 Plant Sign Behav 4 (3): 212-214
Nocturnal breakdown of starch Nocturnal breakdown of malate

16. S.No Plant type Temperature range CO2 compensation point
1 C3 Plant 18-24 deg cel > 50 ppm
2 C4 Plant 32-55 deg cel 2-5 ppm
3 CAM Plant > 40 deg cel 0-5 ppm

17. Yamori W 2012 Plant Physiol doi: 10.1007/s11120-013-9874-6
Temperature based photosynthetic rate

18. Mesophytic plant
https://upload.wikimedia.org/wikipedia/commons/1/1a/Trifolium
Adaptations based
How moderate temperature leads to regulation of homeostasis?

19. Hydrophytic plant
http//:www.pixabay.com/pl/wody-polne-lilie-white-58603
Why plant cell doesn't burst even if we placed in hypotonic solution ?

20. Xerophytic plant
http//:www.pixabay.com/pl/wody-polne-joshua-58603
Main component involved in xerophytes is K/Na ions

21. 1. General cellular structure helps in regulation
2. Transport system in regulation of homeostasis
3. Redox regulation in C3 plants
4. Regulating Malate homeostasis in C4 plant
5. Regulating Carbohydrate metabolism in CAM plants
6. Regulation of ion homeostasis in plants of different
habitats
7. Techniques to study ion homeostasis
8. Regulation of Ca and Mg in plant homeostasis
9. Auxins based homeostasis
10. Overview of various transport system in homeostasis
11. Significance of ion homeostasis
Biochemical basis

22. 1. General cellular structure helps in regulation
Channels Carriers

23. Channels
Taiz L Zeiger E (2002) Plant physiology (3rd edition) oxford: Sinauer Associates

24. K⁺-channels
Osmoticum: Cellular hydrostatic pressure
Develope the membrane potential,
maintenance of cytosolic pH homeostasis
K⁺ channel
classes
Non-voltage-
gated
Voltage
gated

25. Taiz L Zeiger E (2002) Plant physiology (3rd edition) oxford: Sinauer Associates

26. Carriers
Taiz L Zeiger E (2002) Plant physiology (3rd edition) oxford: Sinauer Associates

27. 2. Transport system in regulation of homeostasis
http://www.ib.bioninja.com.au
Primary active transport
Electrogenic transport
Electroneutral transport

28. Secondary Active Transport
http://www.ib.bioninja.com.au

29. 3. Redox Regulation in C3 cycle
C3 acid-based regulation
Michelet L el.al 2013 Front pl sci doi: 10.3389/fpls.2013 .00470
Stress
Activation of all
four enzyme
Elevated level of
carbohydrates
Homeostasis
imbalance
Negative feedback
Changes in PTM
Inhibition of TRX
synthesis
System in balance

30. 4. Regulate malate homeostasis in C4 plant
Regulate malate homeostasis
Taiz L Zeiger E (2002) Plant physiology (3rd edition) oxford: Sinauer Associates
malatemalate
C4 cycle

31. H-Ion as well free oxygen radical
(PH maintain)

32. 5. Regulate carbohydrate metabolism in CAM plant
Ceusters J 2009 Plant Sign Behav 4 (3): 212-214
Malate is the
regulator of PH
homeostasis

33. https://en.wikipedia.org/wiki/Goldenrod
Mesophytes
6. Regulation of ion homeostasis in plants of different habitats

34. Hydrophytes
Osmoregulation
Process of maintaining suitable concentration of solutes and
amount of water in body fluid
http://www.Plants adaptations91155.weebly.com

35. xerophytes
http://www.Plants adaptations91155.weebly.com
How k/Na ions plays important role in homeostasis regulation?

36. 7.Techniques to Study Ion Homeostasis
• Photochemical tools for studying metal ion signaling and homeostasis
• Patch clamp technique to study cell ionic homeostasis under saline conditions
• Channels cloning mutagenesis and expression techniques
• Antibodies as tools for the study of the structure and function of channels protein

37. Photochemical tools for studying metal ion signaling
and homeostasis
Hannah W. 2012 Biochem Pls 51, 7212−7224

38. GFP based protein sensors
Hannah W. 2012 Biochem Pls 51: 7212−7224

39. 8.Regulation of Ca and Mg in plant homeostasis
Tang RJ 2017 Current Opinion in Plant Biology, 39:97–105

40. Tang RJ 2017 Current Opinion in Plant Biology, 39:97–105

41. 9.Role of Auxin
Metabolism in plant
homeostasis
J Michel 2016 development FG & Pl physiol
doi: 10.1242/dev.086363

42. http//:www.ib.bioninja.com.au
10.Overview of various transport system in homeostasis

43. 11. Significance of ion homeostasis in plant.
Passive (dashed arrows)
Active (solid arrows).
http://www.ib.bioninja.com.au
Transport

44. C. Genetic Basis
1. Systemic regulation of mineral homeostasis by micro
RNAs
2. Proposed model of miRNA-mediated signaling network
for regulation of nutrient homeostasis
3. Growth homeostasis is controlled by the Arabidopsis
BON1 gene

45. 1. Systemic regulation of mineral
homeostasis by micro RNAs
Kehr J 2013 flps doi: 10.3389/00145

46. 2. Proposed model of miRNA-mediated signaling
network for regulation of nutrient homeostasis
Paul S 2015 f pl Sci | Volume 6 | Article 232

47. 3. Growth homeostasis is controlled by the
Arabidopsis BON1 genes
Hua J 2017 Genes & development 15:2263–2272
mRNA
Protein
Size of apical meristem

48. Hua J 2017 Genes & development 15:2263–2272

50. Case study-1
Purthy RS 2008 Physiol and Mol Bio of Pl
doi:0.1007/s12298-008-0004-4
Salinity tolerance in Brassica
against Homeostasis
Linking between biochemical and
genetic basis of homeostasis

51. The role of malate in plant homeostasis
• Perturbation of malate metabolism in the TCA cycle
• AtABCB14 and SLAC1 regulate malate homeostasis
Case study-2
AtABCB14 Gene expression Malate
SLAC1 Gene expression Inhibition of malate
synthesis
1. 2.
Unexpected biochemical consequences due to malate metabolism?

52. Malate oxaloacetateMalate dehydrogenase
AtABCB14
Antisense tech
Malate oxaloacetateMalate dehydrogenase
Increase in no of
rhizosphere

53. Conclusion
• Maintaining internal environment constant- Homeostasis
• Stoichiometric hypothesis deals with ionic homeostasis at nutrient
level
• Physiological basis of homeostasis deals thermoregulatory and
ecological adaptation homeostasis
• Ionic homeostasis balances the macro as well as micronutrient in a
plant system
• Genetic basis of homeostasis uncover the plant growth homeostasis.

54. Thank you