Plants produce various antifungal proteins to defend against pathogenic fungi. There are 13 classes of antifungal proteins in plants, including PR proteins, beta glucanases, chitinases, defensins, cyclophilin-like proteins, RIPs, killer toxins, and protease inhibitors. These proteins have different mechanisms of action against fungi, such as degrading the fungal cell wall, forming pores to disrupt membranes, or inhibiting protein synthesis. Continued research is working to discover and characterize novel antifungal proteins with potential applications for controlling fungal diseases.

1. BY SREE REMYA.S
II MSC BIOTECHNOLOGY

2. CONTENTS
• INTRODUCTION
• FUNGAL CELL WALL
• ANTIFUNGAL PROTEINS
• CLASSES OF ANTIFUNGAL PROTEINS & THEIR MECHANISMS
• CONCLUSION

3. INRODUCTION
Fungi are amazing organisms, which can grow in
any surface
Fungi are proficient at colonizing & using plants,
humans & animals as substrate
The fungal cell wall protects the organisms &
relays signals for invasion& infection of a plant,
animal or a human host
Fungi are extremely diverse group of organisms
&some plants have antifungal activity

4. FUNGAL CELL WALL

5. ANTIFUNGAL PROTEINS
Plants are exposed to large number of pathogenic
fungi
Although plants do not have an immune system,
but they have a defense mechanism including
antifungal activity
There are hundred’s of antifungal peptides &
proteins known, with more being discovered
almost daily

6. CLASSES OF ANTIFUNGAL
PROTEINS
o 13 CLASSES OF ANTIFUNGAL PROTEINS ARE
PRESENT:
 PR PROTEINS
PR-1 PROTEINS
PR-2 PROTEINS (beta glucanases)
PR-3 PROTEINS(chitinases)
PR-4 PROTEINS(chitin binding ) proteins
PR-5 PROTEINS(TL)
DEFENSINS
CYCLOPHILIN- LIKE PROTEINS

7. CONT….
RIPs
KILLER PROTEINS (KILLER TOXINS)
PROTEASE INHIBITORS
OTHER PROTEINS

8. ANTIFUNGAL PROTEIN

9. PR PROTEINS
Plants exposed to pathogens such as fungi&
viruses produce low molecular weight
antimicrobial compounds called phytoalexins
These plant proteins called pathogenesis related
(PR) proteins , are divided into 5 groups, PR-1,-2,-
3,-4,-5, based on serological& amino acid sequence
analysis
The 5 classical groups of PR proteins has 2
subclasses:

10. Cont….
A basic subclass found in plant cell vacuole
An acidic subclass found in the extracellular space
PR-1 proteins
 PR-1 proteins accumulates to high levels after
pathogen infection& are antifungal both in
plants& in vitro
 PR-1proteins have been found in wheat, rice ,
maize, tobacco

11. PR-1proteins cont….
PR-1 proteins have antifungal activity at the micro
molar level against no: of plant pathogenic fungi
including Uromyces fabae, Phytophthora
infestans,Erysiphe graminis
PR-1proteins mechanismis unknown
PR-2 PROTEINS
PR-2 have(1,3)beta glucanase activity in vitro & are
grouped into 3 classes on the basis of aminoacid
sequence analysis

12. PR-2 PROTEINS
This proteins found in plants like tobacco, peas,
grains & fruits
The proteins are active at wide range of fungi
including human& plant pathogen(Rhizoctonia
solani, C. albicans, A. fumigatus)
The antifungal activity of PR-2proteins are
demonstrated by no: of invitro enzymes

13. BETA GLUCANASES

14. PR-3 PROTEINS(chitinase)
A no: of enzymatic assays describes PR-3proteins
to have in vitro chitinase activity
Chitinases are isolated from fungi, plants
(tobacco, cucumber, beans)& bacteria have potent
antifungal activity against human& plant
pathogens including T. reesi, Alternia solani,
A.radicina,F.oxysporum)

15. PR-4(chitin binding ) proteins
PR-4proteins have
molecular mass of 13-
14.5 KDa
PR-4proteins are
isolated from potato,
tobacco, barley ,
pumpkins& many
other plant

16. PR-4 PROTEINS CONT….
Chitin binding proteins& have antifungal activity
but are not PR proteins have been isolated from
bacteria, plants, insects
Fungi inhibited by these proteins include plant&
human pathogens eg: Paecilomyces variotii,
F.oxysporum, Aspergillus.sp,A. brassicola
PR-5 ( TL) PROTEINS
PR-5 proteins share significant homology to
thaumatin & are known as TLproteins

17. Cont…
TL proteins have been isolated from A. thaliana,
pumpkin, wheat ,rice
The highly stabilized structure of PR-5 are
resistant to protease degradation
Mechanism is not known
These proteins they are fungicidal against a wide
no: of plant& human pathogens, zeamatin protein
has shown efficacy in murine vaginal model of C.
albicans

18. DEFENSINS
Defensins are low molecular mass cysteine rich
proteins found in mammals, fungi ,insects &
plants
The insecect & mammalian defensins are quiet
small & form voltage depedent ion channels in
plasma membrane
The treatement of hyphae with the defensins from
radish & dhalia cause k+ efflux & Ca+ uptake
through binding to specific cell membrane
receptors

19. COND….
Defensins have the ability to inhibit human& fungal
pathogens including B.cinerea, F.oxysporoum,F.solani
& C.albicans at micromolar levels
CYCLOPHILIN LIKE PROTEIN
Cyclophilins are conserved group of proteins – that are
intracellular receptors for cyclosporin & is found in
bacteria, plant, animal,fungi
A protein isolated from mung bean is called mungin.
Antifungal mechanism is not known

20. RIPs
RIPs are RNA N- glucosidase that depurinates
Rrna,result inarrest of protein synthesis due to
ribosome damage
Plant RIPs inhibit mammalian,bacterial, plant,
fungal protein synthesis
RIPs have been isolated from Pisum sativum,
Viscum album, & from fungi – A.giganteus
RIPs have intrinsic antifungal activity – have ability
to inactivate fungal ribosomes invitro.

21. KILLER PROTEINS (KILLER
TOXINS)
A no: of yeast secrete proteins that are lethal to
sensitive fungal cells.These proteins are killer
toxins are encoded by either by double stranded
DNA,linear double stranded plasmid DNA

22. CONT…
Fungal cells secrete a killer toxin are resistant to
their own toxin but are sensitive to other toxin
Kulveromyces lactis& several Pichia species secrete
a no: of killer toxin
Killer proteins can disrupt cell wall synthesis ,DNA
synthesis,& k+ channel activity – any of these
effect leads to inhibition of fungal cell growth

23. PROTEIN INHIBITORS
Protein inhibitors of serine & cysteine protease
have emerged as antifungal proteins that have
potent activity against plant & animal pathogens.
GRAPH SHOWING THE POTENT ACTIVITY

24. CONT….
Cysteine protease inhibitors are isolated from a no:
of plants & from a group of cystatins, the
phytocystatins
Phytocystatins are active against plant pathogens
such as F. solani,T.reesi

25. CURRENT INVENTIONS
Antifungal activity work is carried out world wide
Viridin a novel protein isolated from culture
protein T. viridae –molecular mass 65 kDa is active
against fungi at 6 micrometer
Snakin -1 is such a novel protein isolated from
potato

26. CONCLUSION
Antifungal proteins & polypeptides have been
isolated from diverse group of organisms
The range of fungi inhibited by antifungal proteins
are extremely broad, & studies about antifungal
proteins are carried out widely