Varu gaitonde genetics of host plant disease resistance
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This document provides an overview of genetics of host plant disease resistance. It defines key terms and discusses early contributions from scientists like Biffin and Flor. It describes the types of genetic resistance, including qualitative and quantitative, and the mechanisms of host-pathogen interaction involving perception, signaling, and response. Examples of resistance genes and their application in plant breeding through marker-assisted selection and other biotechnological approaches are also summarized.
Varu gaitonde genetics of host plant disease resistance
- 2. SEMINAR ON Genetics of Host Plant Disease Resistance 2
- 3. Contents 1. 2. 3. 4. 5. 6. 7. 8. Terminologies Disease and Importance of Host plant Resistance. Scientists contribution. Types of Genetics Resistance. Host Pathogen interaction. R genes application in plant breeding. Resistance Breeding Conclusion. 3
- 4. Terminologies • Elicitor: The signaling molecules. • Effector: Typical proteins that are delivered outside the microbe. • Pathotype: population of a parasite species in which all individuals have a pathogenicity or parasitic ability in common. • Biotype: progeny developed by variant having similar heredity. • PRR-Transmembrane Protein Recognition Receptors. • PAMP/DAMP:Pathogen Associated Molecular Patterns. • PTI: PAMP-Triggered Immunity • ETI-Effector Triggered Immunity. • NBS-LRR-Nucleotide Binding Luicine rich Repeat regions. • MAPK:Mitogen Activated Protein Kinase 4
- 5. Different Pathogens Causing diseases Agrios, G.N. 1998 5
- 6. Biffin(1901) Demonstrated Genetic basis of Disease resistance. Studies conducted on Wheat rust. Obtained 3:1 Mendelian ratio by crossing Rivet x Red king. “Resistance is Heritable” Resistance and susceptibility are independent of other plant characters. 6
- 7. H H Flor(1952) Genetic factors of both plant and pathogen are required for the successful defence response of plant. Wheeler rule-1: Incompatible Reaction Found in Biotrophs. Avr-R recognises each other and their speificity and interaction gives resistence to host. Wheeler rule-2: Compatible reaction Avr-r produce specific compounds ,which interact each other and produce the susceptible response. 7
- 8. Rules of Flor’s Hypothesis(1952) Virulence gene Resistance Gene Incompatibility Avr1 Compatibility avr1 Avr1 avr1 R R R s R1 R S r1 S S Given by Wheeler(1975) 8
- 10. Results From Flor’s Crosses • 25 resistance alleles distributed across 5 loci were identified • Locus # Alleles K1 L11 M6 N3 P4 • For every resistance allele found in the plant, a corresponding virulence allele was found in the pathogen. • There is a gene‐for‐gene interaction between host and parasite. • L and M loci cloned and sequenced in 1995. • 13 different alleles characterized at L locus gave important insights into functions of R‐genes. 10
- 11. 12
- 12. Each race specific r genes has only a limited life span BOOM YEARS Priestley(1970) BUST YEARS 13
- 13. Types of Genetic Resistance • Qualitative Resistance • Distinct classes of resistance and susceptible plants • Controlled by one or a few genes • Also called “Vertical” resistance • Quantitative Resistance • Continuous variation among genotypes • Many loci • Also called “Horizontal” resistance 14
- 14. Genetics of Resistance Mechanisms of resistance: 1.Disease escape 2.Disease endurance. 3.True resistance Classification Based on: 1.Number of Genes 2.Biotype reaction 3.Population/Line concept 4.Evolutionary concept. 5.Specificity. 15
- 15. Defense mechanism in plants 16
- 16. Plant –Pathogen Interaction Perception Signaling Response 17
- 17. Perception How pathogen and host recognize each other.? The gene-for-gene hypothesis between host and pathogen for triggering race-specific resistance. Elicitor – receptor model I- incompatible ,C- compatible 18
- 18. Perception of elicitor signals/ receptors for elicitor signals in plant cell membrane • Salicylic acid, Jasmonic acid and Ethylene • Protein kinase as receptor sites • LRR-type receptors • Lectins as receptors • Resistance gene product as receptors 19
- 19. Secondary messengers(signaling) • Molecules that relay signals from receptors on the cell surface to target molecules. Earl Wilbur Sutherland, discovered secondary messengers, won the 1971 Nobel Prize in Physiology or Medicine. Functions: • They greatly amplify the strength of the signal. • Component of signal transduction cascades. • Secondary messengers. • Calcium ion • Anion channels in signal transduction • Phosphorylation and Phospholipids signaling system • Mitogen-activated protein kinase signaling cascade 20
- 20. Role of Mitogen-activated protein kinase cascade ACS- 1-aminocyclopropane-1-carboxylic acid synthase, (Hamel et al., 2012) 22
- 22. Differential response of plant to pathogens 24 (Yan Zhang et al., 2013)
- 23. Mechanisms of plant defense • Hypersensitive response • Production of reactive oxygen species • Production of antimicrobial metabolites • Defense signal transduction • Synthesis of enzymes (e.g. - chitinases, glucanases) (Nurnberger et al.,2006) 25
- 24. Role of ROS (Thirupathi et al., 2011) 26
- 25. Signaling systems • Alkalization and cytoplasmic acidification • Reactive oxygen species • Nitric oxide in signal transduction • Salicylic acid signaling system • Jasmonate signaling pathway • Ethylene dependent signaling pathway • Fatty acids as systemic signal molecules 27
- 26. Resistant Genes(R Genes) Application in Plant Breeding. 28
- 27. Domain Function Gene LRR Protein-protein interaction. Its major determinants of recognition specificity Pi-ta, Cf 4,9,5 NBS To bind ATP r GTP. Race specificity functions of R gene L6 TIR Race specificity functions of R gene L6 CC Involved in recognition of avr gene product RPW 8 Schematic representation of domains found in plant LRR R proteins. Domains are not drawn to scale. TIR Toll/interleukin-1 receptor, CC coiled coil, NB nucleotide binding, ARC1/2 APAF1, R protein and CED4, LRR leucine rich repeat, SD solanaceous domain, BED BEAF/DREAF zinc finger domain, TM transmembrane, Kin kinase, WRKY WRKY transcription factor 29 (Wladimir et al., 2008)
- 28. Sources of Resistance • Primary Gene Pool • Other breeding programs • Landraces • Germplasm collections (GRIN) • Wild Relatives • Tomato: Lycopersicon genus • Wheat: Agropyron genus • Aegilops tauschii, Triticum monococum • Mutant Transformations: powdery mildew in Barley 30
- 29. Identification of R genes Candidate gene identification by readily designed PCR primers. R gene molecular isolation 2 methods: 1.Map based identification. 2.Transposon tagging 33
- 30. Map based isolation of R genes Genetic marker 1 Genetic marker 2 R gene M3 M4 34
- 31. Map based isolation of R genes 5. Transform a susceptible genotype with a single cosmid clone Disease reaction R R S S Types of problems encountered - A ‘LONGER WALK’ than expected - lack of recombination - An unknown ‘HOLE IN THE BAC CLONE’ RPM1 35 - Which gene is it ? PTO
- 32. Wang and Yano 36
- 33. Map Based Cloning of Pi9 Include recent R gene cloning paper in r 37
- 34. Cloned rice resistant genes Include bullet points of Whole presentation Then conclude 38
- 35. Transposon Tagging of R Genes with genetic selection Tomato Cf-9 : Avr9 Tobacco N gene 30 C 22 C TMV nn NN Transposon inactivation of R gene 39
- 36. R gene expression Very low and constitutive Occasionally low level induction following infection but only in the vicinity of the pathogen Rarely expressed only in resistant genotype - Rice Xa27 – Xanthomonas oryzae pv. oryzae Susceptible alleles 10 bp and a 25 bp insertion in the promoter. (Gu et al, (2005) Science 435: 1122-1125) 40
- 37. How do R proteins function ? Three examples Direct pathogen molecule recognition Indirect pathogen molecule recognition 41
- 38. Direct recognition Tomato Pto - AvrPto Pseudomonas syringae Susceptible host AvrPto or AvrPtoB Resistant Pto host cell wall plasma membrane pto Pto AvrPto and AvrPtoB effectors bind to unknown host target Prf Enhanced pathogen virulence Adapted from Jones and Dangl (2006) Nature HR Less pathogen proliferation 42
- 39. Indirect recognition Arabidopsis RPM1- AvrRpm1 Pseudomonas syringae AvrRpm1 or AvrB Susceptible host No RPM1 NDR1 RIN4 P P P AvrRpm1 effector bind to host target RIN4 and other targets Enhanced pathogen virulence Adapted for Jones and Dangl (2006) Nature NDR1 Resistant RPM1 host RIN4 P P P RPM1 HR Less pathogen proliferation 43
- 40. R Protiens Guard The Virulence Target Avr Susceptible response to favour pathogen growth and development Virulence Target B. INCOMPATIBLE INTERACTION Resistance by guarding Avr Virulence Target R3 AvrB/ AvrRpm1 RIN4 RPM1 Avr2 Rcr3 Cf-2 Resistance response 44
- 41. Approaches for Host Plant Resistant Breeding Breeding for Specific Resistance Individual Major Genes. Breeding for Quantitative traits. Multilines. Marker assisted back crossing. Pyramiding. 45
- 42. Biotechnological approach Marker assisted plants breeding Different markers and application in disease resistance Achievements Tissue culture methods Somaclonal variation Somatic hybridization Genetic engineering (Transgenics) Meristem – Tip culture (for virus free planting material) General breeding approaches-Introduction, Selection, Hybridization Backcross ,Induced mutagenesis 46
- 43. Some examples of molecular markers associated with resistance traits in crop plants (MAS) Host species Resistance gene Marker Reference Pi-2(t), Pi-4 (t) Pi-10 (t) RFLP RAPD Yu et al, 1991 Naqvi et al, 1995 Orseolia oryzae Xa2I Xa3, Xa4, Gm2, Gm4t RAPD RFLP RAPD Zhang et al, 1994 Yoshimura et al, 1995 Mohan et al. 1994 Puccinia recondite Lr9, Lr24 Schachermayr et al. 1994, 1995 Erysiphe graminis Pm1, Pm2, Pm3 RFLP an RAPD RFLP Hartl et al, 1995 Hessian fly H21 RAPD Seo et al., 1997 Maize Leaf blight Rhm RFLP Zaitlin et al. 1993 Barley Stm rust Rpg 1 RFLP Kilian et al 1994 Barley yellow mosaic ym4 RFLP Graner an Bauer, 1993 - RFLP Graner and Tkauz, 1996 - RFLP Ferreira et al, 1995 er RFLP Dirlewanger et al, 1994 - RFLP Young et al, 1992 I2 RFLP Sarfatti et al. 1991 Cladosporium fulvum Cf2/Cf5 RFLP Dickinson et al, 1993 Cyst nematode (Globodera Rostochiensis) HI RFLP Pineda et al, 1993 Rice Pathogen Pyricularia oryzae Xanthomonas oryzae Wheat Rhyncosporium Brassica napus Pea Mungbean Tomato Potato Leptosphaeria maculans Erysiphe polygoni Bruchid Callosobruchus Fusarium oxysporum
- 44. Resistant genes incorporated against specific pathogens through MAB 48
- 48. 52
- 49. 53
Editor's Notes
- #12: FIG. 1. L6 gene DNA probes detect RFLP markers linked to the L and M loci. (A) Map of the L6 region and location of DNA probes. Thelocation of the transcribed region and the two 480-bp direct repeats are indicated with arrows. H, HindIII; Bg, Bgl II; RI, EcoRI; B, BamHI; S,Sph I; X, Xba I. (B) RFLP pattern detected in the parents, Forge (F) and Hoshangabad (H), and some of the 52 test-cross progeny using XbaI-digested DNA and probe LU-2. The presence of the L6 and M resistance genes was determined by inoculation with the appropriate rust strains.The absence of these genes is indicated by a blank square. The positions of the DNA fragments that provide the four RFLP alleles LU2-2A/B (Mlinked) and LU-2-1A/B (L linked) are indicated. In each case, the A allele is derived from Forge and the B allele is from Hoshangabad.by probe
- #19: After evaluation of numerous physiological, biochemical and genetic experiments,
- #20: Genetically defined relationships be-tween salicylic acid (SA)-dependent andethylene–jasmonic acid (ET–JA)-depend-ent defense responses in Arabidopsis.The SA-dependent response is deployedagainst a biotrophic pathogen that ob-tains nutrients from living cells, whereasthe ET–JA response is activated bynecrotrophic pathogens that kill plant tis-sue. Resistance to necrotrophs (but notthe biotroph) is compromised in anArabidopsis mutant (coi1) that does notrespond to JA. Expression of a transgene(NahG) that degrades SA compromisesresistance to the biotroph but not thenecrotrophs. These pathways appear tobe mutually inhibitory.
- #25: RLK-receptor like protien kinase.pdf1.2 gene-a pathogen related gene act as a defensin in arabidopsis.wound related kinase 1.PRR_pattern recognition receptorsTtss-type 3 secretion system
- #27: Superoxidedismutase,catalase,ascorbicparoxidase.
- #33: Fig. 2 Physical map of chromosome 7D in wheat showing markersthat are flanking Lr34/Yr18 and contained within the deletion bin7DS-4 which consists of approximately 39% of the short arm ofchromosome 7D (on the left). The genetic map of the Lr34/Yr18region shows microsatellite markers that flank the resistance genes.Numbers on the left hand side denote genetic distance incentiMorgans. Resistance to powdery mildew (Pm) cosegregatedwith leaf rust and stripe rust resistance. A–D denote confidenceintervals for QTLs for rust resistance previously assigned to thisregion: A QTL for leaf rust and stripe rust identified by Suenagaet al. (2003), B QTL for leaf rust QLr.str-7DS described bySchnurbusch et al. (2004), C QTL for leaf rust QLrP.sfr-7DSidentified by Schnurbusch et al. (2004), D QTL for stripe rustQYr.sgi-7D identified by Ramburan et al. (2004)
- #34: Identification in pib gene isolation.
- #37: Aa sequence is-nbslrr.Duplicated kinase 1a 2a 3a motifs,8cysten residues are clustered in the middle of lrr.
- #38: Contigs –gel readings. Pi9 was introgressed from wild rice Oryzaminuta to cultivated rice line 75-1-127. Tightly linked markers (pBV14, pB8 and pBA14) wereidentified using RAPD and bulk segregant analysis. pB8 was used to screen both BAC and cDNA libraries. A contig was constructed usingpositive BAC clones. Candidate genes, identified from the sequenced contig, were used for transformation. Transgenic lines were evaluatedfor resistance to rice blast.
- #40: Cladosporumfulvum-blue mold
- #43: Pto-psuedomons syringe pv.tomato
- #44: Prr-transmembrain pattern recognition receptorsRlps –arabidopsis receptor like proteinsRIN4-A 211 AMINO ACID ACYLATEd,and plasma membrane associate protien,is type 3 effector gaurded by nbs-lrr.AvrRpm1 or avrb are the 2 unrelated protiens
- #51: Fig. 3. Strategy for engineering broad-spectrum resistance by induction of Avr/Rtransgene combinations. A pathogen Avr gene is expressed in plant cells as atransgene, under the control of a plant promoter that is induced by a range ofpathogens. A corresponding R gene (either endogenous or a transgene) is alsoexpressed. Upon pathogen attack, the pathogen-responsive promoter is activated,the Avr gene is expressed, and the Avr protein interacts with the R protein toinduce the HR and other defense responses. Note that this system can be activatedby any pathogen (or spurious stimulus) that is capable of activating the promoterof the Avr gene.
- #52: Fig. 4. Regulation of defense gene expression by NPR1. NPR1 has an importantrole in ‘local’ resistance triggered by some R genes, as well as two types of sys-temic resistance: Systemic acquired resistance (SAR), which is induced by nectro-tizing pathogens on foliar tissue and which acts through salicylic acid (SA); andinduced systemic resistance (ISR), which is induced by soil-dwelling bacteria andacts through jasmonic acid (JA) and ethylene (ET) [5]. These cascades trigger anas-yet unknown posttranslational modification of NPR1 (depicted by a red star).NPR1 then translocates from the cytoplasm to the nucleus [53]. Once inside thenucleus, NPR1 interacts with TGA transcription factors, and perhaps other pro-teins, to regulate transcription of defense-associated genes [54,55].