This document discusses pathogenesis-related (PR) proteins found in plants. It begins with definitions, noting that PR proteins are produced when plants are infected by pathogens and act to decrease susceptibility. It then describes 17 types of PR proteins classified into families based on their properties, with examples like chitinase and glucanase. Mechanisms of action are discussed, such as degrading fungal cell walls. The document concludes by outlining applications for transferring PR protein genes to transgenic plants to engineer resistance against pathogens like fungi and bacteria.

1. “PR PROTEIN”
By
KAUSHAL KUMAR SAHU
Assistant Professor (Ad Hoc)
Department of Biotechnology
Govt. Digvijay Autonomous P. G. College
Raj-Nandgaon ( C. G. )

2. SYNOPSIS
•Introduction
•Definitions
•Types of PR proteins
•Some important PR proteins
•Mechanism
•Functions
•Application
•Conclusion
•Reference

3. INTRODUCTION
Pathogenesis-related (PR) proteins are proteins produced in plants
in the event of a pathogen attack.
They are widely distributed in plants in trace amounts but are
produced in much greater concentration.
Varying types of PR proteins have been isolated from each of
several crop plants.
They are either extremely acidic or basic so they are highly
soluble and reactive.

4. Protein induced in several plant species when they
are infected by viruses, viroids, fungi or bacteria.
They form a protective barrier against pathogens by
collecting at infection sites and act to decrease
susceptibility of plants. They may have anti-fungal or
anti-bacterial activity
DEFINATION

5. Families
Type
member
Properties
PR-1
PR-2
PR-3
PR-4
PR-5
PR-6
PR-7
PR-8
Tobacco PR-1a
Tobacco PR-2
Tobacco P, Q
Tobacco ‘R’
Tobacco S
Tomato Inhibitor I
Tomato P69
Cucumber chitinase
Antifungal
β-1,3-glucanase
Chitinase type I,II, IV,V,VI,VII
Chitinase type I,II
Thaumatin
Proteinase- inhibitor
Endoproteinase
Chitinase type III
TYPES OF PR PROTEIN

6. Types
member Properties
Familie
s PR-9
PR-10
PR-11
PR-12
PR-13
PR-14
PR-15
PR-16
PR-17
Tobacco ‘lignin forming peroxidase’
Parsley ‘PR1’ Ribonuclease
Tobacco ‘class V’ chitinase
Radish Rs- AFP3
Arabidopsis THI2.1
Barley LTP4
Barley OxOa (germin)
Barley OxOLP
Tobacco PRp27
Peroxidase
Defensin
Thionin
Lipid- transfer protein
Oxalate oxidase
Oxalate oxidase-like
Unknown
Chitinase type I

8. SOME IMPORTANT PR PROTEINS
CHITINASE
Constituent of fungal cell walls which can hydrolysed by the enzyme chitinase.
A bacterial chitinase gene obtained from a soil bacterium was introduced and expressed.
Transformed tobacco plants were found to be resistant to infection of the pathogen Rhizoctonia
solani.
GLUCANASE
Its an another enzyme that degrades the cell wall of many fungi.
The most widely used glucanase is β-1, 4-glucanase.
It has been isolated from barley, introduced, and expressed in transgenic tobacco plants.
By this approach, fungal resistant tobacco, tomato and carrot have been produced
THIONINS
It provide protection against bacteria.
Showed resistance to Pseudomonas syringae

9. LYSOZYME
Degrades chitin and peptidoglycan of cell wal in this way fungal infection
can be reduced.
Transgenic potato plants with lysozyme gene providing reistance to
Eswini carotovora
DEFENSINS
They are antimicrobial peptides found in all plants.
They attack the microbial plasma membrane, however this is not adequate to
provide resistance to pathogen.
So artificial defensins have been produced to provide resistance.

10. MECHANISM

11. APPLICATION
To produce Transgenic Plants
Plan
ts
Gene
transfered
Resistance against
pathogens
Tobacco
Tobacco
Tobacco
Rice
Carrot
Tomato
Brassica napus
Chitinase from bacterium Alternaria longipes
Bean chitinase
Chitinase & 1,3-β glucanase
Chitinase
Chitinase & 1,3-β glucanase
Chitinase & 1,3-β glucanase
Chitinase
Rhizoctonia solani, Phytopthora
parasitica
Cercospora nicotinae
Rhizoctonia solani
Alternaria dauci. A. radicina
Fusarium oxysporoum
Rhizoctonia solani

12. An important common function of most PRs is their
antifungal effects.
Some PRs also exhibit antibacterial, insecticidal or
antiviral action.
Function as signals that spread “news” of the infection
to nearby cells.
Chitinase, Peroxidase, ribonuclease and lysozyme
activities.
FUNCTIONS

13. PR proteins play important role in
disease resistance.
The increasing knowledge about the PR
proteins gives better idea regarding the
development and defense system of
plants.
CONCLUSION

14. Plant pathology:-Fourth edition,1997, By:GEORGE.N.AGRIOS
Plant Tissue Culture: By U.Satyanarayan
en.wikipedia.org/wiki/Pathogenesis-related_protein
Agrios GN. Plant Pathology, 4th ed. San Diego, p: 93-114; 1997
V. Borad, S. Sriram, Pathogenesis-Related Proteins for the
Plant Protection Asian J. Exp. Sci.,22( 3), 2008; 189-196
REFERENCES