Carotenoids, also called tetraterpenoids, are organic pigments that are produced by plants and algae, as well as several bacteria and fungi. Carotenoids can be produced from fats and other basic organic metabolic building blocks by all these organisms.

1. University of Warwick

2. It is more than just a pigment !
CAROTENOIDS

3. BIOSYNTHESIS PATHWAYS
IN PLANTS
Muhammed Sadiq
2012-09-119

4. Overview
1. Introduction
2. Chemical structure
3. Functions of carotenoids
4. The carotenoid pathway
5. Insilico analysis
6. Biotechnological
applications
7. Conclusion
8. Reference

5. Introduction
 Carotenoids are 2nd most abundant pigment with more than
750 members.
 In 1831 Wackenroder isolated carotene from carrots and in
1837 Berzelius named the yellow pigments from autumn
leaves, xanthophylls.
 Carotenoids are C40 lipophilic isoprenoid.

7. β-Carotene supplements are widely used as oral sun
protectants
***Why some ripen fruits shows
green color?

9. Chemical structure
Carotenoids are tetraterpenoids, 40C, built from four terpene
units each containing 10 carbon atoms
Backbone contain 15 conjugated double bonds
Carbon units are linked by alternating single and double bonds.
 Amount of conjugated double bond changes wavelength of light
it can absorb, vary in colors from red, orange and yellow

10. Structure of common carotenoids

11. Oxygenated carotenoids are termed as xanthophylls.
Carotenoids structures containing fewer than 40 carbon atoms --
- Apocarotenoids.
Oxidative degradation and enzymatic cleavage changes flavor
and nutritional quality.

12. Apocarotenoids
 Cleavage products of parent carotenoids. (CCD)
 ABA - from 9-cis-violoxanthin and 9-cis-neoxanthin
 Strigolactones.
 β - ionone
 In animals vitamin A and its derivatives (retinoids).

13. Functions of carotenoids
 In chloroplast and chromoplast
 Biological properties

14. Chloroplast
Carotenoids absorb light in blue region of the spectrum (400
to 600 nm), transferred to chlorophylls.
Singlet to singlet transfer
 Quenching excess light in the form of chlorophyll triplet state
energy transfer
 Zeaxanthin prevent lipid peroxidation through out thylakoid
membrane.

15.  Transfer as vibrational heat into the surrounding medium.
 Carotenoids account for ~20-30% of all light harvested
 Carotenoids may also serve as conductors of electrons.

17. Chromoplast
 Chromoplasts are carotenoid-containing plastids
 Main function of chromoplast carotenoids is the attraction of
pollinating insects and animals.
 Acylated xanthophylls required for the formation of chromoplast
structures

19. Biological properties
Anticarcinogenic effects.
Anti-inflammatory effects.
Radical scavenging
activity.
Antiobesity
Improve visual function
Influences gene expression
and immune function.
Prevention of cardiovascular
disease.

20. Antioxidant Properties
Stabilization of singlet oxygen by physical and chemical
nature.
Chemical stabilization involves the union between the
carotenoid and the free radical. In physical, conversion into low
energy state.
Skin protection
 Scavenging of reactive oxygen species.

23. University of Illinois

24. University of Georgia

25. Cardiovascular Disease Prevention
LDL oxidation showed β-carotene carried in LDL is oxidized
prior to the onset of oxidation of LDL polyunsaturated fatty
acids
Antiobesity effects
 (UCP1) expressed only in BAT , key molecule
 Fucoxanthin reduced WAT and promote expression of UCP1

26. Age-related Macular Degeneration
Macula, or yellow spot, part of the retina and area of
maximum visual.
Lutein, protective effects on macula and prevents cataract
development.
Effects of lutein on AMD - absorbing harmful light,
quenching singlet oxygen and other free radicals

28. Can beta-carotene cause cancer ?
Free-radical-rich atmosphere produced by the chemicals in cigarette
smoke and the resultant inflammatory response in the lung with
complex secondary reactive oxygen and nitrogen species enhance
the formation of unusual b-carotene oxidant and other reactive
species (Journal of the National Cancer Institute)
Adverse effects of high-dose beta carotene on lung cancer incidence
and overall mortality ... related to the pharmacologic doses of beta
carotene used

29. The carotenoid pathway
Synthesis of carotenoid precursors
Two isoprene isomers, isopentenyl diphosphate (IPP) and
its allylic isomer dimethylallyl diphosphate (DMAPP).
2 pathways exist for IPP production in plants: MVA and
MEP pathway.

30. IPP and DMAPP for carotenoid biosynthesis in plants are
from the MEP pathway
MEP pathway uses glyceraldehyde 3-phosphate and
pyruvate as initial substrates to form DXP, catalyzed by
DXS.
MEP is formed by a intermolecular rearrangement and
reduction of DXP by the enzyme DXR

31. B- Carotene
biosynthesis

32. Xanthophyll Biosynthesis

33. IPP isomerase
Catalyses formation of DMAPP from IPP, a reversible
isomerization reaction.
 cDNAs for IPP isomerase identified in Arabidopsis, lettuce,
Brassica, cassava, Sweetpotato and number of other plants.
Two distinct cDNAs for this enzyme, Ipp1 and Ipp2, identified
in Arabidopsis.

34.  Yet, no more than two different cDNAs or
genes identified for this enzyme in any plant.
DXS and DXR are important in carotenoid flux
regulation
Both enzymes are encoded by single genes and
rate-determining enzymes.

35. Synthesis of Geranylgeranyl Pyrophosphate
GGPS catalyzes successive condensation reactions.
Condensation of IPP and DMAPP to form GGPP
Sequential addition of three IPP molecules to DMAPP,
catalyzed by (GGPS), gives 20-carbon molecule GGPP.

36. GGPP synthase (GGPPS)
 Multifunctional enzyme.
Antibodies against GGPPS purified from Capsicum annuum
chromoplasts.
In Arabidopsis, five different cDNA with sequential similarity
to pepper GGPP synthase, identified.

37. Synthesis of Phytoene
First dedicated step of carotenoid biosynthesis
(PSY) catalyzes conversion of two molecules of GGPP into
prephytoene pyrophosphate (PPPP) and into phytoene.
Two molecules of GGPP are joined by condensation reaction
with loss of hydrogen and diphosphate group, results
phytoene.

38. First PSY gene(pTOM5) identified from tomato leaves.
Phytoene synthase genes also cloned from plants like maize,
pepper, Arabidopsis and Narcissus etc.
In tomato (PSY1), identified in fruits, PSY2 present in leaves
and PSY3 in roots function under stress condition.
Maize & rice PSY3 – abiotic stress induced ABA formation.

39. Regulation of PSY
Increase activity of DXS induce PSY expression in potato &
tomato.
PSY is negatively regulated by (P1F1) TF during seed de-
etiolation.
Reduced amount of α-carotene modulate PSY protein levels.
Epigenetic factors.

40. Desaturation of phytoene
Colorless compound phytoene into yellow, orange, and red
carotenoids
Catalyzed by two related enzymes in plants: phytoene
desaturase and ζ-carotene desaturase.
 Carotenoid biosynthesis is redox regulated via carotene
desaturase.

41. Cyclization of Lycopene
Cyclization of linear carotenoid : one branch leads to β-
carotene and xanthophylls and other to α-carotene and lutein.
Lycopene b-cyclase catalyses formation of bicyclic b-carotene
from lycopene in plants
This enzyme introduces two b-rings at the ends of the linear
lycopene molecule forms β carotene and (ε,β) ring forms α-
carotene and xanthophyll

42. 1 ε-LCY gene identified in Arabidopsis and tomato,
Arabidopsis contains a copy of β-LCY , but two β-LCY
copies, Crtl-B and Cyc-B identified in tomato.
Keto lycopene cyclase relates to capsanthin–capsorubin
synthase of pepper and the neoxanthin synthase of tomato
and potato.
Down regulation of ε-LCY shows enhanced accumulation of
β-carotene, zeaxanthin and violaxanthin.

43. Cyclic carotenes to xanthophylls
Oxygenated derivatives of carotenes
Cyclic carotenes can be modified by hydroxylation to
generate xanthophyll
Hydroxylation of β carotene yields zeaxanthin.
ZEP hydroxylates β ring of zeaxanthin – antheraxanthin &
violaxanthin --- Neoxanthin by NSY

44. Two different types of carotenoid hydroxylases
(CHYs)
1. Non-heme di-iron enzymes (BCH type), catalyze
hydroxylation of b rings
2. Cytochrome P450 enzymes (CYP97 type), catalyze
hydroxylation of both b and e rings

45.  Genome-wide search and identified putative candidates for
PSY gene in 34 sequenced plants
 Phylogenetic analysis shows PSY evolved independently in
algae as well as monocotyledonous and dicotyledonous plants.
 Amino acid motifs in algae and plants are highly conserved.
 Study provided a theoretical basis for learning evolutionary
relationships.
Insilico analysis of carotenoid pathway

48.  Identified 67 carotenoid biosynthetic genes in B. rapa,
orthologs of the 47 carotenoid genes in A. thaliana
 46 were successfully mapped to the 10 B. rapa chromosomes.
 Expression analysis of the carotenoid biosynthetic genes
suggested that their expression levels differed among organs.
 Study of carotenoid biosynthetic genes in B. rapa provides
insights into carotenoid metabolic mechanisms of Brassica
crop.

49. Synthetic carotenoids
Commercially available synthetic carotenoids used as
food colorants,
b-carotene,
b-apo- 8'-carotenal (apocarotenal)
canthaxanthin.
good stability in food applications.

50. Biotechnological applications
Production of smart crops.
Vitamin, medicine and dietary supplement formulations.
Production of insect resistant plants by introducing β-ionone
Production of Golden rice, Super banana
Production lycopene enriched tomatoes

52. Conclusion
Carotenoid biosynthesis pathways are extensively studied because
of its diverse functions. Future research will address the key
questions related to the coordinated organization of different
components of carotenoid pathway to assemble ‘‘metabolons’’ in
a known sub organellar location.

53. Reference
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B. D., Chen, S., Schaal, B. A., and Silv, J. P. 2016. Natural variation in
expression of genes associated with carotenoid biosynthesis and accumulation
in cassava (Manihot esculenta Crantz) storage root. BMC plant biology. 16:133.
2. Han, Y., Zheng, Q. S., Wei, Y. P., Chen, J., Liu, R., and Wan, H. J. 2015. In
silico identification and analysis of phytoene synthase genes in plants. Genet.
Mol. Res. 14(3): 9412-9422.
3. Li, P., Zhang S., Shifan zhang., Li, F., Zhang, H., Wu, J., Wang, X., and Sun,
R. 2015. Carotenoid biosynthetic genes in Brassica rapa: Comparative genome
analysis and expression profiling. BMC Genomics. 16: 492.

54. 4. Mendes, A. F. D. S., Soares, V., and Costa, M. 2015. Carotenoid
biosynthesis genomics. Springer. 10:107.
5. Naik, P. S., Chanemougasoundharam, A., Khurana, S. M. P., and
Kalloo, G. 2003. Genetic manipulation of carotenoid pathway in
higher plants. Current science. 85:10.
6. Nisar, N., Li, l., Lu, S., Khin, N. C., and Pogson, B. J. 2015.
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55. Thank you