2. Introduction
• Welcome to the presentation on R-Genes: the defenders of plant
immunity.
• Today, we'll explore the central dogma process in the context of R-Genes
and their role in protecting plants against pathogens.
3. Introduction to R-Genes
• R-Genes, or Resistance Genes, are a crucial component of plant
immunity.
• They encode proteins that recognize and respond to pathogen
invasion, activating defense mechanisms to protect the plant.
• R-Genes play a vital role in both direct defense responses and
systemic acquired resistance.
4. Structure of R-Genes
• R-Genes typically contain conserved domains, such as nucleotide-
binding sites (NBS) and leucine-rich repeats (LRR).
• The NBS domain binds and hydrolyzes nucleotides, facilitating
signal transduction.
• The LRR domain is involved in protein-protein interactions,
allowing for pathogen recognition.
5. Activation of R-Genes
• When a plant is infected by a pathogen, specific molecules, known as
avirulence (Avr) proteins, are released by the pathogen.
• The Avr proteins are recognized by the corresponding R-Genes in the
plant, triggering a defense response.
• This recognition activates signal transduction pathways, leading to the
expression of defense-related genes.
6. Central Dogma and R-Gene Activation
• The central dogma process plays a critical role in R-Gene activation
and the subsequent defense response.
• Transcriptional activation leads to the synthesis of defense-related
mRNA molecules.
• Translation of these mRNAs results in the production of proteins
involved in plant defense mechanisms.
7. Overview of Central Dogma
• The central dogma of molecular biology describes the flow of
genetic information within a biological system.
• It consists of three main processes: DNA replication, transcription,
and translation.
8. • Central Dogma: DNA codes for RNA which guides the synthesis of
proteins.
• DNA: “Master blueprint", contains all genetic info of an organism. Must
be protected; therefore it never leaves the nucleus.
• RNA: “Temporary blueprint", copies small portions of DNA and can
leave nucleus to synthesize proteins at the ribosome.
• Proteins: Primary building block of organisms. A macromolecule made
of linked monomers called amino acids.
9. DNA Replication
• DNA replication is the process by which a cell duplicates its DNA.
• It occurs during the S phase of the cell cycle and ensures that each
daughter cell receives an identical copy of the genetic material.
• This process is crucial for the inheritance of genetic information.
10. Transcription
• Transcription is the process of synthesizing messenger RNA
(mRNA) from a DNA template.
• It occurs in the nucleus and is catalyzed by the enzyme RNA
polymerase.
• Transcription is the first step in gene expression and plays a vital
role in regulating cellular functions.
11. Translation
• Translation is the process of protein synthesis, where the information
encoded in mRNA is used to assemble a specific sequence of amino
acids into a polypeptide chain.
• It occurs in the cytoplasm at the ribosomes.
• Transfer RNA (tRNA) molecules deliver amino acids to the ribosome
based on the codons present on the mRNA.
12. Examples of R-Gene Mediated Defense
Mechanisms
• Hypersensitive response (HR): Rapid cell death at the infection site,
preventing the spread of the pathogen.
• Systemic acquired resistance (SAR): Induction of defense responses
throughout the plant, enhancing resistance to future infections.
• Production of antimicrobial compounds: Synthesis of compounds
toxic to pathogens, such as phytoalexins and pathogenesis-related
proteins.
13. ADVANTAGE OF R-GENE
• When induced in timely manner, the concerted response efficiently halt
pathogen growth with minimal collateral damage to the plant.
• No input is required from the farmer and no adverse environmental effects.
• Efficient reduction of pathogen growth.
• Minimal damage to the host plant.
• zero input of pesticides from the farmers and
• Most importantly the environment friendly nature of such crops.
14. DISADVANTAGE OF R-GENE
• R-genes are quickly defeated by co-evolving pathogens.
• Many R genes recognise only a limited number of pathogen strains.
• R genes do not provide broad spectrum resistance.
• Introgression of R genes into a elite cultivars by convention breeding is
a lengthy process.
15. Conclusion
• R-Genes are essential components of plant immunity, providing
defense against a wide range of pathogens.
• Understanding the central dogma process helps elucidate the molecular
mechanisms underlying R-Gene activation and plant defense responses.
• Continued research in this area is crucial for developing strategies to
enhance crop resistance and ensure global food security.
