role of cytokinin in seed development, mechanism and applications

1. Role of cytokinin in seed
development

2. Role of cytokinin in seed
development

3. Cytokinesis

4. PHYTOHORMONES
Phytohormones are organic
compounds which are
either synthesized in
laboratories or produced
naturally within the plants.
They profoundly control
and modify the
physiological processes like
the growth, development,
and movement of plants

5. 1940-1950s

6. J. Wiesner (1892)
Specific Chemicals involved
in cell division
Haberlandt (1913)
Wounding induced cell division
in Plant tissue culture.
Ex:- Potato parenchyma

7. Identified as 6-(furfuryl
amino) purine
Skoog
Kinetin(Not natural)

8. Extracted Zeatin from Maize
endosperm
Also found in
coconut milk
Naturally occurring
Adenine base
Miller
Modified form of Adeninie termed as Kinetin
Kinetin is a form of cytokinin

9. Structure
Adenine
 Nomenclature proposed by Letham (1978)
[9R]Z
Zeatin ribose
(diH)Z
Dihydrozeatin

11. iPMP-dependent pathway
iPMP-independent pathway
Adenosine
Precursor
Dimethyallyl pyrophosphate
(DMAPP)
Isopentenyl adenosine-5’-
diphosphate
ADP ATP
Isopentenyl adenosine-5’-
triphosphate
Hydroxylase
Zeatin

12. ip ribotide tZ ribotide cZ ribotide
Activation of Cytokinin
Kudo, 2010
DMAPP
+
ADP/ATP
IPT CYP735A
DMAPP + tRNA
Trna-IPT
Prenyl-tRNA
ip riboside tZ riboside cZ riboside
ip tZ cZ
CKX
Degradation
LOG

13. Inactivation & Reactivation
Degradation
(Joseph J, 2014)
Trans-zeatin
N7 - glucosylzeatin
N9 - glucosylzeatin
O - glucosylzeatin
N-glucosyltransferase O-glucosyltransferase
O-glucosidase

15. Sensor Histidine kinase Response regulator
Input Transmitter Output
Receiver
Ligand
P
Transcription of
response genes
Hybrid sensor histidine kinase Response regulator
AHP(His phosphotransfer protein)
Input Receiver
His Kinase
Ligand
P
ATP
Receiver Output
P P
Two Component System

16. Cytoplasm
Nucleus
CHASE Domain
H
D D
H
CK
ATP
H
D D
H
P
P
AHP
P
AHP
P
AHP
P
Receiver Output
Type B ARR Type A ARR Transcription
CK Response
Type A ARR
P
CK Response
Receptor: CRE 1
EX: AHK2,AHK3, etc..
Ligand: Cytokinin(CK)
Phosphate transferer-AHP
Detailed Signalling

17. Cell division
Removes
inhibitory
phosphate
Promotes
accumulation
of G1 Cyclins
Role of cytokinin

18. Cotyledon growth
No CK
CK
(Bakalova et al., 2003)

19. Cell growth and cell division in cotyledons
during the seedling development

20. Cotyledon expansion
Xanthium cotyledon pieces in the presence or absence of benzyl
adenine (10-5 M).
Y. Esashi2 and A. C. Leopold

21. Organ differentiation
 More auxin and Cytokinin Root formation
 Auxin and more Cytokinin Shoot formation
Cytokinin promotes overall development of cell

22. Effect of Auxin + Cytokinin
Root formation
Callus initiation
(monocots)
First stage of
embryogenesis
Callus initiation in
dicots
Adventitious
shoot formation
Adventitious shoot
proliferation
Auxin Cytokinin

23. (Jameson, 2015)

24. Senescence

25. The hormone
causes delay in the
process of ageing
and senescence
During this effect, there is
prevention of the protein
degradation and nutrient
immobilization
The molecules like the chlorophyll
pigments in the leaf are not degraded.
This prevents the ageing and the
falling of the leaves
Richmond Lang effect

26. Commercial Application

27. Lupin
Less
Successful
in Legumes
Repeated
application
Overcome
Prevented flower abortion or
pod set
Increased yield
Prevented flower
abortion or pod set
Increased yield
IPT + Flower
specific
promoter
Atkins

29. Case Study-1

30. Field experiment was carried with two winter wheat
(Triticum aestivum L.) cultivars Sadovo 772 and Geya-1,
produced through the conventional selection method.
Treatments
(1) untreated control plants
(2) in situ priming with (6-BAP) at 10 mg/L twice at grain filling
stage
(3) in situ priming with kinetin (6-furfurylaminopurine) at 10 mg/L
twice at grain filling stage
Experimental section

31. Low temperature storage
Two samples were prepared from 250 g seeds for each
variant of the field experiment. Seeds were dried to 6%
moisture content and transferred for storage for 12 months at
–18 °C.

32. Analysis of seed viability after exposition to
low temperature stress
Seeds from control and CK-primed plants were germinated on
moist filter paper in Petri dishes at 22 °С for 120 h.
After 5 days of germination, the
degree of coleoptile and root
growth was assessed.

33. Soil pot experiment was conducted with seedlings
descended from the three variants of the field experiment.
Seeds were sown in pots containing 1 kg dry soil and grown for
15 days in the greenhouse, fully developed
leaves were collected for the analyses
Pot Experiment

34. Grain Yield
Geya-1 Sadovo 772

35. Growth parameters of Flag leaves

36. Viability after cold storage (5 days old seedlings)

38. Growth parameters (15 Day old seedling)

39. Cell membrane stability
(15 Day old seedling)
(5 Day old seedling)

40. Oxidative stress markers

41. Conclusion
• Priming with CK significantly improved germination, seedling
vigour and growth parameters
• The average accumulation of malondialdehyde and H2O2 from
low temperature stored seeds of field primed plants was
estimated lower, which contributed to higher cell membrane
stability.
• CK priming was more pronounced in the modern cv. Geya-1
compared to the older cv. Sadovo 772 and could be attributed
to improved anti-aging mechanism connected with better
protection against oxidative damage.

42. CASE STUDY-2
Phosphorelay- involves histidine kinases, histidine phosphotransfer
proteins (HPs), and response regulators (RRs)

43. Experimental Section
• The rice (Oryza sativa subsp. japonica)cultivar, Zhonghua11 (ZH11) was
used as background for overexpression analyses.
• A population containing more than 25 000 lines was generated for the
screening and d48, referring to dlt-based double mutant No.48, was
identified.
• The homozygous single mutant s48 was generated by backcross with ZH11
using d48 at least three times.
• Rice plants were grown in the field under natural conditions.

44. Morphology
Grain morphology of ZH11 and s48. s48 (+/−) indicates grains of heterozygous plants

45. Seedling of ZH11
and s48 treated with or
without kinetin (KT− or KT+,
10 μM), a synthetic cytokinin

46. Callus greening induced by
cytokinin (t-zeatin) combined
with NAA (1 μM)

47. Effect of cytokinin
on dark-induced
leaf senescence in
ZH11 and s48
Relative expression
of osRRs

48. N-Asparagine
E-Glutamic acid
Y-Tyrosine
H-Histidine
D-Aspartic acid
Variations of Amino acids in PPKL1

49. Grain morphology overexpressing PPKL1

50. Conclusion
• Mutation at a specific amino acid D364 of PPKL1 activates
cytokinin response and thus enlarges grain size in a semi-
dominant mutant named s48.
• Overexpression of PPKL1 containing D364, either with the
deletion of the phosphatase domain or not, rescues
the s48 mutant phenotype

51. Summary
• Cytokinins positively regulate agriculturally important traits
such as grain size and biomass.
• Promote unfavorable phenotypes such as inhibition of root
elongation.
• Under stress conditions, the source may be limiting yield.
Under such conditions, IPT gene ameliorate the impacts of
stress on yield by increasing the source capacity.

52. • Spatio-temporal regulation of cytokinins is
required for appropriate function in
specific organs
• In order to better utilize cytokinin action
to enhance beneficial traits of crops, a
deeper understanding of their temporal
regulation will be necessary
Future Prospectus