Horizantal gene transfer in evolution of nematodes


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This is a presentation on Horizontal gene transfer(HGT) in evolution of nematodes which gives us idea about importance of HGT in evolution of nematode parasitism. Here I have covered the historical events about HGT as well.

This is my First seminar in Div of Nematology.

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  • Horizantal gene transfer in evolution of nematodes

    1. 1. Horizontal Gene Transfer in Evolution of Nematode Parasitism Priyank H. Mhatre Roll No - 5021 Division of Nematology
    2. 2. Gene A gene is a unit of heredity in a living organism It is a segment of DNA that code for a specific protein Genes hold the information to build and maintain an organism's cells
    3. 3. What is Gene Transfer?
    4. 4. Types of Gene Transfer Vertical gene transfer Horizontal gene transfer
    5. 5. Vertical Gene Transfer Vertical Gene Transfer : transmission of genes from an organism to it’s offspring - Sexual reproduction in higher animals and plants is the way of VGT
    6. 6. Horizontal gene transfer Horizontal gene transfer (HGT) - implies the non-sexual exchange of genetic material between species, in some cases even across kingdoms
    7. 7. History of HGT Frederick Griffith (1879-1941) Joshua Lederberg (1925-2008)
    8. 8. Cont…  Frederick Griffith in 1928 first time seen the transformation in bacteria  J Lederberg in 1946 – 47 first time seen conjugation and in 1956 transduction in bacteria  M Syvanen (1985 ) proposed this mechanism as cross-species gene transfer in evolution  Hilario & Gogarten (1993 ) use the term horizontal gene transfer between organisms as an alternative explanation for those conflictive phylogenetic events (Luis Boto., 2009)
    9. 9. Some facts… HGT is the non-genealogical transmission of genetic material from one organism to another It is a source of new genetic material to the recipient It is a mechanism that permits the acquisition of evolutionary novelties It is common mechanism of gene transfer in bacteria and archaea (Luis boto., 2009)
    10. 10. Types of HGT Ancient HGT Recent
    11. 11. Types of HGT Ancient :- genes transferred between organisms separated a long time ago -The ancient HGT is difficult to detect through codon usage bias and differential base composition Foreign genes in cell once they are part of the same genome support same mutational bias with resident and ameliorated after many generations Recent :- genes transferred between organisms separated recently - Easy to detect based on Criteria of codon usage bias and differential base composition. (Luis Boto., 2009)
    12. 12. How it happens? Transformation HGT Transduction Conjugation Transduction
    13. 13. Magic of Horizontal Gene Transfer
    14. 14. The photosynthetic sea slug Elysia chlorotica appears like a dark green leaf as a result of retaining chloroplasts from its algal prey, Vaucheria litorea, in cells lining of its digestive tract. The sea slug has acquired photosynthesis-supporting genes by horizontal gene transfer and can use the chloroplasts to carry out photosynthesis for several months (Rumpho et al., 2008)
    15. 15. How It Grows? (Rumpho et al., 2008)
    16. 16. Cont… It is also called as “solar-powered” sea slug Nuclear gene of oxygenic photosynthesis, psbO, have been acquired by the animal via HGT Photosynthesis is by the plastids which provides E. chlorotica with energy for its entire lifespan of ∼ 10 months The plastids are not transmitted vertically (i.e. are absent in eggs) and do not undergo division in the sea slug. (Rumpho et al., 2008)
    17. 17. What about nematodes?
    18. 18. Evolutionary History of Nematodes Era Period Millions Year ago CENOZOIC MESOZOIC Cretaceous Jurassic Triassic 65 --- Flowering plants (PPN) 145 200 PALEOZOIC Permian Carboniferous Devonian Silurian Ordovician Cambrian 253--- Insect (EPN) 300 336 440 484 Land Plants 542 --- Nematodes origin (FLN)
    19. 19. Evolution of Parasitism In Nematodes Free-living Phoresy Necromeny Pre-adaptations1. Dauer larvae 2. Toxicity tolerance 3. Low oxygen tolerance Parasitism (Dieterich et al., 2009)
    20. 20. Pristionchus pacificus Found in a necromenic association with scarab beetle representing an intermediate type of association between phoretic and parasites This intermediate association considered as a step toward parasitism In this nematode the number of detoxification enzymes are Increase, in comparison to phoretic nematodes It has also acquired cellulase genes Ppa-cel-1, 2, & 3 via HGT from bacteria and archaea This is the first report of cellulase found in non plant parasitic nematodes (Mayer et al., 2011)
    21. 21. Nematode proteins with their activity Enzymes Cellulase, Xylanases Activity Degradation of cellulose and hemicelluloses Polygalacturonases, Pectate lyases, Degradation of pectins Candidate arabinanases Expansin Soften the plant cell wall (Danchin et al., 2010)
    22. 22. Plant cell wall modifiers with their closest relatives (Danchin et al., 2010)
    23. 23. Phylogenetic Analysis of Polygalacturonases, Pectate lyases, Candidate arabinases (Danchin et al., 2010)
    24. 24. Phylogenetic Analysis of Cellulase, Xylanases., and Expansin. (Danchin et al., 2010)
    25. 25. Cellulase in nematodes Cellulases are enzymes that hydrolyse the β-1,4 linkages of cellulose These genes are acquired via HGT from bacteria, fungus, or other microbes Cellulases are from three structurally and phylogenetically unrelated families found in nematodes :1. GHF5- genes common in PPN 2. GHF16- genes are known from B. xylophilus , B. mucronatus 3. GHF45- genes are known from B. xylophilus
    26. 26. GHF5
    27. 27. Cyst Nematodes 1st report of genes with endogenous cellulase production by animals in absence of cellulolytic microorganisms was in G. rostochinensis and in H. glycines Genes - GR-eng-1 and 2, HG-eng-1 and 2 - oesophageal gland Protein- GR-ENG-1 & 2, HG-ENG-1 & 2 – stylet secretion These genes facilitate the intracellular migration of nematodes through plant roots by partial cell wall degradation These genes show homology with genes of the bacteria like Erwinia chrysanthemi, Clostridium acetobutylicum and B. subtilis ( Smant et al., 1998 )
    28. 28. RKN (M. incognita) Researchers characterized a new β-1,4-endoglucanase gene from the root-knot nematode They identified the gene - MI-eng-2, which is localized in the secretory oesophageal glands cell of all developmental stages of the nematode and the protein secreted is– MI-ENG-2 This protein is involved in plant cell wall degradation during parasitism GHF5 genes result from horizontal gene transfer of a bacterial gene with a cellulose-binding domain (CBD) (Ledger et al.,2006)
    29. 29. ResultsRT-PCR Uninfected tomato roots Lemmi9 primers Unhatched coiled juveniles Freshly hatched J2s Females Males (Ledger et al.,2006)
    30. 30. Cont… In situ hybridization This picture shows that MI-eng-2 gene is present in sub-ventral oesophageal glands of M. incognita (Ledger et al.,2006)
    31. 31. Evolution of Cellulase Genes Linker domain Catalytic domain CBD (Ledger et al.,2006)
    32. 32. GHF16
    33. 33. Bursaphelenchus Large group of nematodes Worldwide distributed Most species are solely fungal feeders and all species rely on fungi as a food source at some stage of their life cycle B. xylophilus - Unique feeding habit i.e. feed on live trees & fungus (both) (Kikuchi et al., 2005)
    34. 34. β-1,3-glucanase in pine wilt nematode β-1,3-Glucanases catalyse the hydrolysis of β-1,3-D-glucosidic linkages in β-1,3-D-glucan This polymer (β-1,3-glucan ) is a major structural component of fungal cell walls thus the protein is allowing the nematodes to feed on fungus This shows that β-1,3-glucanases play an important role in the life cycle of this nematode (Kikuchi et al., 2005)
    35. 35. Cont… Enzymes with their Glycosil Hydrolase FamiliesBacterial , Nematodes - GHF 16 Plant and fungus- GHF 17 Sequences shows that Pinewood nematode B. xylophilus has acquired endo-β-1,3-glucanase (GHF16) by HGT from bacteria like Xanthomonas axonopodis , Pseudomonas spp. etc (Kikuchi et al., 2005)
    36. 36. RESULTS Southern-blot analysis in situ hybridization Southern-blot analysis of Bx-lam16A Genomic DNA from B. xylophilus (N) and B. cinerea (F) were digested with EcoRI (lanes 1 and 3) or HindIII (lanes 2 and 4). The blot was hybridized with a probe generated from Bxlam16A cDNA Localization by in situ hybridization of Bx-lam16A transcripts in the oesophageal gland cells of B. xylophilus adult female with antisense (A) and sense (B) Bx-lam16A digoxigenin - labelled cDNA probes (Kikuchi et al., 2005)
    37. 37. Phylogenetic tree of selected GHF16 Phylogenetic tree of selected GHF16 β-1,3-glucanases and β-1,3-glucanase-like proteins generated using maximum-likelihood analysis (Kikuchi et al., 2005)
    38. 38. GHF45
    39. 39. Life Cycle of B. xylophilus
    40. 40. GHF 45 B. xylophilus is part of clade of PPN (RKN & CN) and not directly related to FFN As this nematode feed on fungus, some genes are horizontally transmitted to the ancestor by fungus Researchers identified a cellulase gene: Bx-eng-1 from this nematode which is from GHF 45 and is similar to the fungus Southern- blot Analysis of Bx-eng-1 digested with EcoR1 or HindIII and the blot was hybridized with a probe generated from Bxeng-1 cDNA. Southern- blot Analysis of Bx-eng-1 (Kikuchi et al., 2004)
    41. 41. in situ hybridization Localization of Bx-eng-1 transcripts in the oesophageal gland cells of B. xylophilus adult female by in situ hybridization. Nematode sections were hybridized with antisense (A) or sense (B) Bx-eng-1 digoxigenin- labelled cDNA probes (Kikuchi et al., 2004)
    42. 42. Evolution of Heterorhabditis-Photorhabdus symbiosis with a marine Lux operon Squid with Lux operon came at seashore Rhabditid enters in it & quiescence occurs Bacteria start feeding on dead squid Nematode feed on bacteria in carcass (Necromeny) Endosymbiotic and squid bacteria mingle Lux gene acquired by endosymbiotic bacteria (Poinar, 1993)
    43. 43. Filarial worm with endosymbionts DNA Wolbachia is a symbiont in the most filarial worm Infected filarial nematodes depend on Wolbachia for proper development and survival Two Filarial species Acanthocheilonema viteae and Onchocerca flexuosa were found without Wolbachia but with DNA of Wolbachia Wolbachia DNA Researchers identified 49 Wolbachia-like DNA sequences in A. viteae and 114 DNA sequences in O. flexuosa (McNulty et al., 2010)
    44. 44. HGT is an important evolutionary novelty present in nature Nematode acquired several parasitic genes by horizontal gene transfer from bacteria, fungus & other microbes to become a potential parasite of plant, animals and other invertebrates Because of HGT Pine wilt nematode got a unique capacity to feed on both live plants and fungi
    45. 45. Heterorhabditid formed a symbiotic association with Photorhabdus and evolved as EPN Some filarial worms are able to survive without Wolbachia as they have acquired DNA of Wolbachia via HGT which plays an important role in their development & survival