Post on 24-Jun-2015
description
Horizontal Gene Transfer in Evolution of Nematode
Parasitism
Priyank H. MhatreRoll No - 5021
Division of Nematology
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
Gene
What is Gene Transfer?
Vertical gene transfer Horizontal gene transfer
Types of 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
Vertical Gene Transfer
Horizontal gene transfer (HGT) - implies the non-sexual exchange of genetic material between species, in some cases even across kingdoms
Horizontal gene transfer
Frederick Griffith (1879-1941) Joshua Lederberg (1925-2008)
History of HGT
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)
Frederick Griffith in 1928 first time seen the transformation in bacteria
Cont…
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
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)
Some facts…
HGT
Recent
Ancient
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
cellonce
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)
Types of HGT
Transduction
HGTConjugation
Transduction
Transformation
How it happens?How it happens?
Magic of Horizontal Gene Transfer
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)
(Rumpho et al., 2008)
How It Grows?
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)
What about nematodes?
CENOZOIC
MESOZOICCretaceousJurassicTriassic
65 --- Flowering plants (PPN)145200
PALEOZOIC
PermianCarboniferousDevonianSilurianOrdovicianCambrian
253--- Insect (EPN)300336440484542 --- Nematodes origin (FLN)
Era Period Millions Year ago
Land Plants
Evolutionary History of Nematodes
Parasitism
Pre-adaptations-1. Dauer larvae2. Toxicity tolerance3. Low oxygen tolerance
Free-living
Phoresy
Necromeny
(Dieterich et al., 2009)
Evolution of Parasitism In Nematodes
This intermediate association considered as a step toward parasitism
Found in a necromenic association with scarab beetle representing an intermediate type of association between phoretic and parasites
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)
Pristionchus pacificus
Enzymes Activity
Cellulase, Xylanases
Degradation of cellulose and hemicelluloses
Polygalacturonases,Pectate lyases,Candidate arabinanases
Degradation of pectins
Expansin Soften the plant cell wall
(Danchin et al., 2010)
Nematode proteins with their activity
Plant cell wall modifiers with their closest relatives
(Danchin et al., 2010)
(Danchin et al., 2010)
Phylogenetic Analysis of Polygalacturonases, Pectate lyases, Candidate arabinases
Phylogenetic Analysis of Cellulase, Xylanases., and Expansin.
(Danchin et al., 2010)
Cellulases are enzymes that hydrolyse the β-1,4 linkages of cellulose
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
These genes are acquired via HGT from bacteria, fungus, or other microbes
Cellulase in nematodes
GHF5
These genes show homology with genes of the bacteria like Erwinia chrysanthemi, Clostridium acetobutylicum and B. subtilis
These genes facilitate the intracellular migration of nematodes through plant roots by partial cell wall degradation
1st report of genes with endogenous cellulase production by animals in absence of cellulolytic microorganisms was in G. rostochinensis and in H. glycines
( Smant et al., 1998 )
Genes - GR-eng-1 and 2, HG-eng-1 and 2 - oesophageal gland Protein- GR-ENG-1 & 2, HG-ENG-1 & 2 – stylet secretion
Cyst Nematodes
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)
RKN (M. incognita)
Results-
(Ledger et al.,2006)
Uninfected tomato roots
Unhatched coiled juveniles
Freshly hatched J2s Females
Males
Lemmi9 primers
RT-PCR
In situ hybridization
This picture shows that MI-eng-2 gene is present in sub-ventral oesophageal glands of M. incognita
Cont…
(Ledger et al.,2006)
(Ledger et al.,2006)
Evolution of Cellulase Genes
Linker domain
CBD
Catalytic domain
GHF16
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)
Bursaphelenchus
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
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)
β-1,3-glucanase in pine wilt nematode
Enzymes with their Glycosil Hydrolase Families-
Bacterial , 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)
Cont…
RESULTS -
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 Bx-lam16A cDNA
(Kikuchi et al., 2005)
Southern-blot analysis
in situ hybridization
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
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)
GHF45
Life Cycle of B. xylophilus
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 Bx-eng-1 cDNA.
(Kikuchi et al., 2004)
GHF 45
Southern- blot Analysis of Bx-eng-1
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
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
in situ hybridization
(Kikuchi et al., 2004)
Endosymbiotic and squid bacteria
mingle
Rhabditid enters in it & quiescence
occurs
Squid with Lux operon came at
seashore
Bacteria start feeding on dead
squid
Nematode feed on bacteria in carcass
(Necromeny)
Lux gene acquired by endosymbiotic
bacteria
Evolution of Heterorhabditis-Photorhabdus symbiosis with a marine Lux operon
(Poinar, 1993)
Wolbachia 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
Researchers identified 49 Wolbachia-like DNA sequences in A. viteae and 114 DNA sequences in O. flexuosa
(McNulty et al., 2010)
Filarial worm with endosymbionts DNA
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
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