It deals about what is aquaporin , Classification, Structure and its role in plant growth and development.

1. AQUAPORIN - A
PROMISING PROTEIN FOR
AGRICULTURE
1

2. Liquid Gold of Life
2
Photosynthesis
Transpiration

3. Pathway ofWater Absorption
3

4. WaterTransport
Transport
mechanism
Active
Transport
Passive
Transport
Diffusion
Facilitated
Diffusion
Channel
Protein
Carrier
Protein
4

5. Carrier Protein Classification
•Uniport
•Symport
•Antiport
5

6. Major Intrinsic Proteins (MIPs)
2. GLPs (glycerol facilitators) - Glycerol and neutral molecules
3. GLAs (aquaglyceroporins) - Both water and glycerol
Channel Protein Classification
6

7. Table of the Contents
Aquaporin
Structure of aquaporin
Classification of aquaporin
Regulation of aquaporin
Role of aquaporin in plant growth and development
Research findings
Conclusion
7

8. • Water channel protein
• Major intrinsic proteins (MIPs) family
• Transport of water, small neutral solutes (urea, boric
acid, silicic acid) or gases (ammonia, carbon dioxide)
• Molecular weight - 23 to 34 kDa (Gomes et al., 2009)
• Found in all life forms - Plants, humans, animals,
bacteria, fungi (Maurel et al., 2001)
Aquaporins (AQPs)
(Chrispeels and Maurel, 1994)
8

9. Why Aquaporins Needed
9

10. Maurel et al. (1993) - First plant aquaporin , Arabidopsis thaliana tonoplast intrinsic
protein (AtTIP; 1)
The first aquaporin described was the mammalian AQP1 (Agre 1992)
Workman (1990) - Demonstrated the functional expression of water channel
Wayne et al. (1987) - Nodulin-26, GmNoD26 was identified in soybean
Johnsen et al. (1953) - First proposed the specialized pores
Solomon et al. (1950) - Work on water permeability
History of Aquaporins
10

11. Discovery of AQPs
In 1992-First aquaporin CHIP 28 ('aquaporin-1’)
In 1999- Three-dimensional structure of an aquaporin
In 2003- Won Noble Price in Chemistry
Peter Agre
11

12. Structure of AQPs
• Six Transmembrane α helices (1-6)
• Homotetramers
• N and C terminal located in Cystol
• Five loops (A- E)
• Two intracellular and three extracellular
helix loops
(Scheuring et al., 1999).
12

13. 13
Contd…
AQPs Structure

14. • ‘Hourglass model’ - Cryoelectronic microscopy
(Walz et al., 1997)
• Wide external opening and narrow centre
Shape of AQPs
Hourglass fold
14

15. 1. NPA domain (Size exclusion zone)
N- Asparagine
P- Proline
A- Alanine
Selectivity Filters
15

16. 2. Ar/R selectivity – Aromatic/Arginine
• Histidine, Arginine & Arspargine
16

17. 3. Proton Filter
17

18. • Mass Spectrometry (Santoni et al., 2003)
• Quantitative RT-PCR (Hachez et al., 2006)
• High resolution technique (Marmagne et al., 2004)
Identification and characterization of AQPs
18

19. 1) Plasma membrane intrinsic proteins (PIPs)
2) Tonoplast intrinsic proteins (TIPs)
3) Nodulin intrinsic proteins (NIPs)
4) Small basic intrinsic proteins (SIPs)
5) Uncharacterized intrinsic proteins (XIPs)
6) Glycerol intrinsic proteins (GIPs)
7) Hybrid intrinsic proteins (HIPs)
8) Large intrinsic proteins (LIPs)
Classification of AQPs
(Maurel et al. 2015)
19

20. Contd…
PIPs
• PIP1 and PIP2
• PIP1;1 & PIP1;5
TIPs
• TIP1, TIP2, TIP3, TIP4 and TIP5
• TIP1;1 and TIP1;2
NIPs
• NIP1, NIP2 and NIP3
• NIP1;1 and NIP1;2
SIPS
• SIP1 and SIP2
• SIP1;1 and SIP1;2
(Deshmukh et al., 2015)
20

21. Functions of AQPs
• Largest part of AQP subfamily
• Plasma membranes, vascular tissues, guard cells
• Several amino acids at C-terminal
• Among 35 AQPs genes in Arabiodiopsis, 13 gene encodes
for PIPs (Gupta et al., 2009)
• PIP1 – (PIP1:1 to PIP1;5)
• PIP2- (PIP2:1 to PIP1;8) (Maurel et al., 2007)
PIPs
21

22. • Most abundant AQPs
• Tonoplast
• First protein in Arabidopsis (Johnson et al., 1990)
• TIP1, TIP2, TIP3, TIP4 and TIP5
• TIPs isoforms are found in vacuoles
• Transporting small solutes and gases
• Water permeability is higher (Fleurat et al., 2005)
TIPs
Contd…
22

23. • Nodulin protein
• Root nodule
• Entoplasmic reticulum (ER)
• Located in leguminous plant
• Transporting water between bacteria and host plant
• NIP1, NIP2 and NIP3
• NIP1 - Transport water and lactic acid,
• NIP2 and NIP3 - Metalloids such as silicic acid, boric acid,
arsenic acid, selenite and germanic acid
• Maintaining plant water balance (Weig et al., 1997)
NIPs
Contd…
23

24. • Small subfamily
• Very short cytosolic N terminal
• SIP1 (SIP1;1 and SIP1;2)
• Moderate water transport activity
SIPs
Contd…
• New subfamily discovered in cotton
• Transport water, metalloids, hydrogen peroxide
XIPs
24

25. 25
Species PIPs NIPs TIPs SIPs XIPs GIPs HIPs LIPs Total
Zea mays L. 12 08 18 03 - - - - 41
Oryza sativa L 11 10 10 02 - - - - 33
Hardeum vulgare L 20 08 11 01 - - - - 40
Soghum bicolor L 09 10 13 03 - - - - 35
Brassica rapa L 23 15 16 06 - - - - 60
Brassica oleracea L 25 17 19 06 - - - - 67
Phaseolus vulgaris 12 10 10 04 02 - - - 66
Citrus sinensis L 08 09 11 03 03 - - - 34
Solanum tuberosum L 15 10 11 03 08 - - - 47
Solanum lycopersicum L 14 12 11 04 06 - - - 47
Gossypium hirsutum L 28 12 23 07 01 - - - 71
Jatropa curca L 09 08 09 04 02 32
(Ahmed et al., 2020)
Table: 1 Detailed account of aquaporins (AQP) genes in different species

26. Function of AQP in mineral nutrition
(Wang et al., 2016)
26

27. 1. Post translational modification
 Phosphorylation,
 Methylation,
Acetylation,
Deamination
 Glycosylation
2. Gating
Phosphorylation,
Proton (H+)
Mode of AQPs regulation
( Deshmukh et al., 2020)
27

28. 28
(Maurel et al., 2015)

29. Plant
aquaporin
subfamily
Localization
Physiological functions Regulation
Tissue Sub cellular
TIP
Seed, Leaf,
Root
Tonoplast Transport of water,
urea, ammonia,
Phosphorylation
NIP
- Peri bacteroid
membrane
Transport of water,
glycerol
Phosphorylation
SIP
- Endo plasmic
reticulum
- -
PIP
Roots, Shoots,
Leaf, Flowers
Plasma membrane Transport CO2, glycerol,
water
Phosphorylation
Table:2 Regulation of plant aquaporin
29

30. Aquaporin Inhibitors
30
(Singh, et al., 2020)
Note:
• Sodium naphthenates, Sodium Azide, Cycloheximide, Naphthenates , Sulfhydryl reagents
• Inhibition of Sulfhydryl group by 2- mercaptoethanol

31. • Multifunctional membrane proteins
• Involved in gaseous exchange such as O2 and CO2; transportation of small solutes -
urea, NH3, Si, B, ROS (Deshmukh et al., 2016)
• Plant growth and development – Cell division and cell differentiation
• PIPs and TIPs - Upregulated in vascular and meristematic regions and might influence
plant development (Maurel et al., 2008)
• In Arabidopsis, AtTIP1;1 - Highly expressed in root, flower, stem and leaves (Ludevid et
al., 1992)
Role of AQPs in plant growth
31

32. • TIP1;1 -Plant growth hormone GA3 - Increased cell size, root enlargement, and expansion
of tonoplast membrane (Phillips and Huttly, 1994)
• PIPs in lateral root primordia emergence - Auxin downregulate the expression and
functions of aquaporin genes (Peret et al., 2012)
• AtPIP1b - Enhancement of growth rate, stomatal density, transpiration rate and
photosynthetic efficiency (Aharon et al., 2003)
• Seed-specific aquaporins - Rice, Arabidopsis, Soybean, Canola and flax (Shivaraj et al.,
2017).
Contd…
32

33. Role of AQPs in seed germination
Orthodox Seed germination
33
(Wang et al ., 2020)

34. • Overexpression of PIP in Arabidopsis, rice &
tobacco - Enhanced Carbon conductance and
CO2 assimilation (Flexas et al., 2006)
• A 60–70% inhibition of mesophyll CO2
conductance by application of aquaporin
inhibitor (mercuric chloride) (Terashima and
Ono, 2002)
Role of AQPs in CO2 movement
34
(Gao et al., 2018)

35. Drought Stress
Early Drought Triggered AQPs activity
Prolonged drought Inhibition AQPs activity
• PIPs and TIPs upregulated during drought (Alexandersson et al., 2005)
• AtPIP2;6 and AtSIP1;1 were insensitive to water-deficient conditions
• PIPs and TIPs are the primary class - Upregulated during the drought in
roots, leaves and flowers (Deshmukh et al., 2016)
Role of AQPs in abiotic stress
35

36. Contd…
(Ahmed et al., 2020)
AQPs role in drought 36

37. Salinity stress
Early stage – Reduced water uptake
• In Arabidopsis – PIPs and TIPs are triggered (Boursiac et al., 2005)
• NIP from wheat - Highly upregulated (Gao et al., 2010)
• Most of the aquaporins in citrus were upregulated in roots (Martins
et al., 2015)
• In barley - Downregulation of AQP expression (Kirch et al., 2000)
Contd…
37

38. (Bhardwaj et al., 2013)
AQPs role in salt stress
38

39. Role of AQPs & ROS
(Maurel et al., 2015) 39

40. • Plant biotic interaction
• GmNOD26 - First Aquaporin - Peri bacteroid membrane
(Wallace et al., 2006)
• GmNOD26 - Ammonium transport from the bacteroid -
Maintains osmoregulation in the plant cytosol and
bacteroid (Hwang et al., 2010)
• NIPs constitute 10% of the total proteins on the
symbiosome membrane (Clarke et al., 2014)
Role of AQPs in plant biotic interaction
40

41. (Afzal et al., 2016)
41
Plant aquaporin in response to environmental conditions

42. Genes Species Localization Response References
AtPIP1-4 Arabidopsis thaliana Leaf Up regulation Alexanderson et al. (2005)
AtTIP1-1 Arabidopsis thaliana Leaf Down regulation Alexanderson et al. (2005)
PIP2-1 Vitis vinifera Shoot tip Down regulation Cramer et al. (2007)
OsPIP1-1 Oryza sativa Leaf Up regulation Guo et al. (2006)
PtPIP1-1 Populus trichocarpa Root Down regulation Calvo-Polanco et al. (2019)
PvPIP1,
PvTIP1
Phaseolus vulgaris L Leaf Up regulation Zupin et al. (2017)
Table 3 :Differential response of aquaporin genes to drought stress
42

43. Four subfamilies – Humans
• Water-specific channels (AQP0, 1, 2, 4, 5, 6) - Water
• Aquaglyceroporins (AQP3, 7, 9, 10) – Water, Urea, glycerol
• Water and ammonium aquaporins (AQP8) – Water , Ammonium
• Unorthodox aquaporins (AQP11, 12)
Aquaporin in human and their role
43
(Finn et al., 2014)

44. Contd…
44

45. 45

46. Finding 1: Expression of aquaporin subtypes (GhPIP1;1, GhTIP2;1 and
GhSIP1;3) in cotton (Gossypium hirsutum) submitted to salt stress
Treatments details:
• Stress treatment (ST) - V3 stage—21 d after emergence during 72 h
• Seven Genotypes - BRS, Serido, 7MH, Acacia, MT 152, DP555, FMT 701 and BRS
416
• Salt solution (NaCl 95 mM)
• At the end of stress treatment, root tissues were used to total RNA extraction,
and RT–qPCR analyses for AQP expression
(Braz et al., 2019) 46

47. Contd…
Fig1: Relative expression of GhPIP1;1, GhTIP2;1 and GhSIP1;3 in cotton plants submitted to short salt stress
(Braz et al., 2019)
47

48. Finding 2: Drought stress and re-watering affect the abundance of TIP
aquaporin transcripts in barley
• Sebastian Variety
• Soil moisture 12% estimated by TDR
• Drought imposement - Moisture content reduced from 3 %
• Rewatering was given
• The relative expression of the HvTIP genes was assessed in RT-qPCR
48
(Kurowska et al., 2019)

49. Fig2: Relative water content in barley under drought, re-watering and control conditions
(Kurowska et al., 2019)
49

50. Fig3: Expression patterns of HvTIP genes under drought stress and re-watering in barley leaves
(Kurowska et al., 2019)

51. 0
5
10
15
20
25
PIP1b2 PIP1b3
Stomatal density
Upper Leaf Surface LowerLeaf Surface
Fig 4: Stomatal density
Fig 5: PIPs expression on physiological parameters
51
Finding 3: Overexpression of a plasma membrane aquaporin in
transgenic tobacco improves plant vigor
(Aharon et al., 2003)
0
10
20
30
40
50
60
Transpiration rate Photosynthesis
rate
Chlorophyll
flourescense
PIP1b2 PIP1b3

52. Finding 4: A banana aquaporin gene, MaPIP1;1, is involved
in tolerance to drought and salt stresses
Fig 6: MaPIP1;1 expression in
different banana organs (A) and in
leaves and roots with stress
treatments (B,C,D)
(Xu et al., 2014)
52

53. • Multifunctional channel protein
• AQPs mainly PIPs, TIPs, and NIPs, to facilitate the transport of water and
plant mineral nutrients across plasma membranes and cell organelles
• AQPs expression to modulate the water, mineral nutrient uptake,
utilization, improve the water and nutrient use efficiency in plants, as well
as increase tolerance to biotic and abiotic stress
53
Conclusion

54. 54