Tospovirus-thrips interactions

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1 welcome

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2 Tospovirus-thrips interactions Anitha.C.N. PAK 5091

History: 

3 Spotted wilt - Australia (1915). Samuel et al. (1930) – Tomato spotted wilt virus (TSWV). Francki &Colleagues- similarity between TSWV and viruses in the family Bunyaviridae History

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4 Thrips O : Thysanoptera S.O : Terebrantia F : Thripidae Viruses F : Bunyaviridae G : Tospovirus Taxonomic position

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5 Bunyaviridae Orthobunyavirus Hantavirus Nairovirus Phlebovirus Tospo virus - Plant Pathogenic Thrips transmitted member Plant families susceptible : 110 identified families Plant species susceptible : 857 named species Animal infecting

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6 Tospovirus Thrips vector CaCV = Capsicum Chlorosis Virus Ceratothripoides claratris CSNV = Chrysanthemum Stem Necrosis Virus Frankliniella occidentalis, F. schultzei GRSV = Groundnut Ring Spot Virus F. occidentalis, F. schultzei, F. intonsa, F. gemina INSV = Impatiens Necrotic Spot Virus F. occidentalis, F. schultzei, F. intonsa IYSV = Iris Yellow Spot Virus T. tabaci MYSV = Melon Yellow Spot Virus T. palmi PBNV = Peanut Bud Necrosis Virus Scirtothrips dorsalis PCFV = Peanut Chloratic Fan Virus S. dorsalis PYSV = Peanut Yellow Spot Virus S. dorsalis PSMV = Physalis Severe Mottle Virus Unknown TCSV = Tomato Chloratic Spot Virus F. occidentalis, F. schultzei TSWV = Tomato Spotted Wilt tospovirus F. occidentalis, F. schultzei, F. intonsa, F. gemina, F. bispinosa, T. tabaci, T. setosus, TYFRV = Tomato Yellow Fruit Ring Virus T. tabaci, Microcephalothrips abdomanalis TYRV = Tomato Yellow Ring Virus Thrips noted but not identified WBNV = Watermelon Bud Necrosis Virus T. palmi WSMoV =Watermelon Silver Mottle Virus T. palmi ZLCV = Zucchini Lethal Chlorosis Virus F. zucchini

Characters of virus and vector: 

7 Characters of virus and vector Tospoviruses replicate in their thrips vector. Insect not only spread the virus but also serve as virus host. Thrips can’t transmit tospoviruses unless they acquire the virus during their immature stages. When larvae feed on infected plants, ingested virus crosses the midgut barrier and enters salivary glands. Transmission then occurs when the virus moves into the plant with the saliva during feeding.

(Cont’d): 

8 (Cont’d) A midgut barrier in adults prevents ingested virus from moving to the salivary gland. Insect remain infective for life but there is no evidence of transovarial passage. Seed transmission of tospoviruses is not known to occur. Tospoviruses also spread through vegetatively propagated material.

Tospo virus Characteristics: 

9 Tospo virus Characteristics Spherical virus Particles, 110 nm in diameter. Tripartite RNA genome Surrounded by a lipid membrane contains two Viral-encoded glycoproteins (G N and G C ). Genetically diverse, rapidly emerging and infects disparate hosts.

Virus-Vector relationship: 

10 Virus-Vector relationship Virus can be acquired by the larval stage. Transmission is due almost exclusively to adult thrips. Larvae can acquire within 15 min. but incubation period of 3 to 10 days (depending on vector species). After infective, can transmit the virus in 15-20 min. of feeding time & can transmit for a maximum period of 22-30 days or till death. Overlapping stages in the life cycle can account for continuous virus spread in nature.

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11 Fig: Electron micrograph of purified TSWV particle (left) and TSWV RNPs (right)

Genomic RNA segments: 

12 Genomic RNA segments Small (S) RNA - codes in ambisense arrangement for a non- structural (NS) Protein and Nucleoprotein Medium (M) RNA - viral movement protein (NSm) , - common precursor to the glycoproteins Large (L) RNA - RNA-dependent- RNA –Polymerase

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13 Fig : Diagram of TSWV Virion

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14 Fig : Genomic organization and expression strategy of Tomato Spotted wilt virus

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15 The thermal inactivation point : 40-43.75 to 45 o C Longevity in vitro : 0.2-0.6 to 1 days Dilution end point : 2-3 The infectivity is decreased by treatment with ether, lost when deproteinized with proteases, phenol or detergent Physicochemical and Physical properties

Transmission: 

16 Transmission Transmitted - Vector Mechanical inoculation Grafting Not transmitted - By contact between hosts Seeds Pollen Virus transmission – semi-persistent or Persistent propagative manner

Some of the symptoms caused by tospo virus and thrips interaction: 

17 Some of the symptoms caused by tospo virus and thrips interaction Deformity on nectarine from thrips feeding Deformity on peanut leaves from thrips feeding Scarring and corky tissue on nectarines resulting from thrips feeding Dimpling resulting from thrips egg-laying Halo spots on grape from thrips egg-laying tomato infected by tomato spotted wilt virus.

Symptoms: 

18 Symptoms Necrotic/ chloratic ring patterns on leaves, stem . Wilting and purpling of leaves and stem can occur. Young leaves frequently turn bronze, develop numerous small dark brown lesions (Tomato) . The entire plant may be stunted with drooping leaves suggestive of a vascular wilt. Black berry necrotic lesions -Onion Tomato

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19 Tomato Spotted wilt Virus

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20 Slightly raised areas, faint concentric rings. Obvious rings - red & white / red & yellow Bud necrosis - PBNV Yellow spot- PNYS Tospovirus

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21 Tomato Spotted Wilt Virus in pepper Citrus thrips scarring on mature orange Halo spots on mature grapes around thrips oviposition punctures, visible as small scars. Crop damaged by western flower thrips.

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22 Fig : Conditions driving rapid co- evolution between Thrips vector and Tospoviruses CO-EVOLUTION OF THRIPS AND TOSPO VIRUS

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23 Fig: Thrips life cycle and Tospo virus transmission cycle

TOSPOVIRUS – THRIPS INTERACTION: 

24 TOSPOVIRUS – THRIPS INTERACTION

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25 Fig: Thrips internal organs and their putative role in virus passage to the salivary glands Hg, Hindgut; Mg, midgut; E, esophagus; EF, efferent salivary duct; L, lumen; Psg, Primary salivary glands S, cross section of muscle; Tsg, tubular salivary glands; VP, Viroplasm: DM, dense mass Virus dissemination and replication in vector thrips

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26 Fig: Accumulation of TSWV in developing larvae , prepupa, and adults of transmitting F.occidentalis and non-transmitting T.tabaci population as analysed by using ELISA using antibodies to its N protein. ( Nagata et al., 2002)

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27 (Wijkamp et al., 1993) Multiplication of TSWV in its vector F. occidentalis Fig: Production of N protein and NS protein in TSWV infected and healthy larvae of F. occidentalis

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28 Fig : western blot analysis of extract from larvae and adults sampled at at 2h AAP using antiserum against the TSWV N protein and NSm protein (Wijkamp et al., 1993)

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29 Fig: Relationship between L1/L2 ratio of thrips larvae at acquisition and subsequent transmission efficiency of the resulting adults. (Fannet et al., 1996) Thrips stage dependent acquisition of tospoviruses

Is TSWV a pathogen to Thrips?: 

30 Is TSWV a pathogen to Thrips?

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31 Fig: Mean number of Thrips recovered in three replicates on TSWV infected or non infected Thrips resistant pepper plants A. Choice B. Non choice tests Infected-Shaded bars non infected- white bars Preference of Thrips for TSWV infected versus non infected Pepper plants ( Maris et al., 2004)

Table: Mean duration of the developmental stages of Franklienella occidentalis reared on TSWV infected and non infected pepper &Datura stramonium plants : 

32 Table: Mean duration of the developmental stages of Franklienella occidentalis reared on TSWV infected and non infected pepper & Datura stramonium plants Plant Health status Length of a developmental stage (days) Egg Larval Pre pupal Pupal No. of days from egg to adult Capsicum annum (TS) Infected 3.0 4.7 1.0 2.2 10.9 Non infected 3.4 5.2 1.0 2.5 12.1 C. annum Mazurka RZ Infected 3.3 4.4 0.9 2.0 10.6 Non infected 3.6 5.9 1.2 2.2 12.9 Datura stramonium Infected 3.1 4.6 1.1 2.3 11.1 Non infected 3.4 6.1 1.1 2.1 12.7 (Maris et al ., 2004)

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33 Fig: a) Relationship between survival and age b) cumulative reproductive potential for INSV exposed and unexposed Frankliniella occidentalis (Deangelis et al., 1993)

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34 Includes complex series of events– fusion of viral and host membrane, virus binding to molecules on host cell Virion entry commonly occurs by one of two mechanisms P H independent entry- direct fusion viral membrane with host plasma membrane P H dependent entry – formation of cellular compartment (endosome) or fusion with an acidic compartment (Lysosome). Virus entry mechanisms

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35 Endocytic Pathways Clathrin-mediated pathway Caveolae pathway Macropinocytosis pathway Non-clathrin mediated pathway Non-caveolae mediated pathway

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36 Fig : Major routes of endocytosis used by viruses (Sara B. et al., 2002)

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37 GPs play important role in virus infection of thrips and thrips acquisition Important virulence of Bunyaviruses Involved in virus attachment and entry into the host cells GN : Contains an arginine-glycine-aspartic acid near the N-terminus which is characteristic of cell adhesion molecules Involved in virus binding and entry Gc :Serve as fusion protein mediating entry into the insect cells TSWV glycoproteins

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38 Fig: In vivo thrips feeding experiment showing that soluble G N (G N -S) inhibits acquisition of TSWV. (Anna et al ., 2004)

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39 Fig: In vivo thrips feeding experiment showing that soluble G N (G N -S) inhibits acquisition of TSWV. A ) TSWV alone ( B ) TSWV and G N -S. (Anna et al ., 2005)

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40 Fig: Genetic determinants of TSWV lie on the viral M RNA in the ORF encoding GN and Gc Viral genetic determinants for thrips transmission of TSWV

Thrips transmissibility of reassortants : 

41 Thrips transmissibility of reassortants Fig: Genotype analysis of two parental isolates and six reassortants (Sang-hoon sin et al ., 2005)

Table: Thrips transmissibility of reassortants : 

42 Table: Thrips transmissibility of reassortants Reassortants Transmission Genotypes L D M D S D 0/10;0/10;0/10 NA L R M R S R 6/9;3/10;2/10 L R M R S R L R M R S D 4/10;2/10;2/10 L R M R S D L R M D S D 0/10;0/10;0/10 NA L R M D S R 0/10;0/10;0/10 NA L D M D S R 0/10;0/10;0/10 NA L D M R S R 4/10;3/10;3/10 L D M R S R L D M R S D 4/10;2/10;2/10 L D M R S D (Sin et al., 2004)

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43 Fig: Gel overlay assay of dissected midguts from Frankliniella occidentalis and extracts of whole Schizaphus graminum , with gel-isolated tomato spotted wilt virus (TSWV) glycoproteins (GPs) as the overlay. ( Bandla et al., 1997) Role of TSWV GPs as viral attachment proteins

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44 Fig: Labeling of first instar western flower thrips midgut membranes with anti-idiotype antibodies to tomato spotted wilt virus membrane glycoproteins (GP1 and GP2). A. Control, dissection reacted with normal serum. B. midgut cells do not fluoresce. Arrows indicate the location of the midgut. C. Dissection reacted with the anti-idiotype to GP1. D. Plasma membranes (plasmalemma) bounding the midgut epithelial cells fluoresce specifically. E. Dissection reacted with the anti-idiotype to GP2. F. Basal membranes of the midgut fluoresce specifically. B=body H = hindgut; S1 &S2 = two lobes of the primary salivary gland (Bandla et al., 1997)

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45 Weed species Percent infected weed species Percent transmission Jagtial Palem Rajendranagar Ageratum conyzoides 8.11 21.82 13.33 12.5 Achyranthus aspera 5.13 2.73 6.42 10.0 Alysicarpus rugosua 11.67 17.91 18.00 27.0 Commelina bengalensis 6.25 10.29 6.38 22.8 Vigna trilobata 27.78 26.92 17.31 32.3 Gopal, (1998) Table : Proportion of PBNV infected weeds and the efficiency of Thrips palmi in virus acquisition from weed hosts

Management: 

46 Management Cloth mesh row covers that exclude insects. Reflective mulches are used to repel insect pests and improve plant growth. Monitoring insects by beating or shaking a rose terminal. Using a yellow sticky trap in a greenhouse crop.

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47 Traps for western flower thrips. Adult fungus gnat (left), thrips (center), and whitefly (right) in a yellow sticky trap.

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48 Adult Thripobius parasite on greenhouse thrips. Adult predatory mite, Euseius tularensis, eating a citrus thrips nymph Biological control Amblyseius cucumeris Amblyseius degenerans

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49 Orius insidiosus beauveria Minute pirate bug

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50 Thrips are commonly eradicated using endosulfan, chlorpyrifos, bendiocarb, and synthetic pyrethrinoids (Parrella 1995a). Classes of insecticides registered for use on WFT include organophosphates, carbamates, pyrethrinoids, insect growth regulators, chlorinated hydrocarbons, chloronicotinyls, spinosyns, macrocyclic lactone, microbials, and horticultural oils (Robb 1998). Chemical control

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51 The effects of two insecticides on the population dynamics of thrips and the minute pirate bug. ( Danitol , SpinTor ) Managing thrips and tomato Spotted Wilt in pepper (Joe et al ., 1998) Danitol spinTor Untreated

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52 The effects of uv -reflective mulch on the population dynamics of thrips and the minute pirate bug. (Joe et al ., 1998) Uv reflective mulch Black mulch

Control - Problems: 

53 Control - Problems Eggs are inserted into leaf/petal tissue which protects from insecticides. I stage larvae usually protected in flower buds and terminal foliage. Both the larval stages feed in the protected areas. At the end of II stage, larvae stops feeding and moves down into soil of crop litter to pupate. Thus avoids insecticides. Insecticide resistance – quick. Feeding causes collapse of plant cells (leading to non reaching to toxicity), leading to deformed plant growth, silvery and flecking. Cultural and Varietal selections are the other options.

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54 conclusion

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55 Thank you