An overview of the Agrobacterium-mediated gene transfer process. Moreover, studied different kinds of Agrobacterium species are involved in this mechanism.
Agrobacterium is a rod-shaped, Gram-negative bacteria found mostly in the soil. It is a plant pathogen that is responsible for causing crown gall disease in them. This bacteria is also known as the natural genetic engineer because of it's the ability to integrate its plasmid Gene into the plant genome.
Agrobacterium tumefaciens transfer of their genetic material T-DNA of Ti-plasmid into the plant cell: A: Agrobacterium tumefaciens; B: Agrobacterium genome; C: Ti Plasmid : a: T-DNA , b: Vir genes , c: Replication origin , d: Opines catabolism genes; D: Plant cell
A Ti-Plasmid (tumor-inducing plasmid) is a ds, circular DNA that often, but not always. It's a piece of genetic equipment that transfers genetic material from bacterial cells means Agrobacterium tumefaciens into plant cells used to induce tumors in the plant. The Ti-plasmid is damage when Agrobacterium is grown above 28 °C. Such cured bacteria don't induce crown gall disease in the plant due to they are avirulent. The Ti-Plasmid are classified into two types on the basis of opine genes are present in T-DNA.
The Plasmid has 196 genes that code for 195 proteins. There is no one structural RNA. The plasmid is 206.479 nucleotides long. the GC content is 56% and 81% of the genetic material is coding genes.
The modification of this plasmid is a very important source in the production of transgenic plants.
The T-DNA must be cut out of the circular plasmid. A VirD1/D2 complex nicks the DNA at the left and right border sequences. The VirD2 protein is covalently attached to the 5' end. VirD2 contains a motif that leads to the nucleoprotein complex being targeted to the type IV secretion system (T4SS).
In the cytoplasm of the recipient cell, the T-DNA complex becomes coated with VirE2 proteins, which are exported through the T4SS independently from the T-DNA complex. Nuclear localization signals, or NLS, located on the VirE2 and VirD2 are recognized by the importin alpha protein, which then associates with importin beta and the nuclear pore complex to transfer the T-DNA into the nucleus. So that the T-DNA can integrate into the host genome.
We inoculate Agrobacterium containing our genes of interest, onto wounded plant tissue explants. The Agrobacterium then transfers the gene of interest into the DNA of the plant tissue.
Introduction
Ti plasmid
Agrobacterium tumefaciens
Ti plasmid structure
Overview of infection process
Ti plasmid derived vector systems
Cointegrate vectors
Binary vectors
Agrobacterium mediated transformation of explants
Conclusions
References
An overview of the Agrobacterium-mediated gene transfer process. Moreover, studied different kinds of Agrobacterium species are involved in this mechanism.
Agrobacterium is a rod-shaped, Gram-negative bacteria found mostly in the soil. It is a plant pathogen that is responsible for causing crown gall disease in them. This bacteria is also known as the natural genetic engineer because of it's the ability to integrate its plasmid Gene into the plant genome.
Agrobacterium tumefaciens transfer of their genetic material T-DNA of Ti-plasmid into the plant cell: A: Agrobacterium tumefaciens; B: Agrobacterium genome; C: Ti Plasmid : a: T-DNA , b: Vir genes , c: Replication origin , d: Opines catabolism genes; D: Plant cell
A Ti-Plasmid (tumor-inducing plasmid) is a ds, circular DNA that often, but not always. It's a piece of genetic equipment that transfers genetic material from bacterial cells means Agrobacterium tumefaciens into plant cells used to induce tumors in the plant. The Ti-plasmid is damage when Agrobacterium is grown above 28 °C. Such cured bacteria don't induce crown gall disease in the plant due to they are avirulent. The Ti-Plasmid are classified into two types on the basis of opine genes are present in T-DNA.
The Plasmid has 196 genes that code for 195 proteins. There is no one structural RNA. The plasmid is 206.479 nucleotides long. the GC content is 56% and 81% of the genetic material is coding genes.
The modification of this plasmid is a very important source in the production of transgenic plants.
The T-DNA must be cut out of the circular plasmid. A VirD1/D2 complex nicks the DNA at the left and right border sequences. The VirD2 protein is covalently attached to the 5' end. VirD2 contains a motif that leads to the nucleoprotein complex being targeted to the type IV secretion system (T4SS).
In the cytoplasm of the recipient cell, the T-DNA complex becomes coated with VirE2 proteins, which are exported through the T4SS independently from the T-DNA complex. Nuclear localization signals, or NLS, located on the VirE2 and VirD2 are recognized by the importin alpha protein, which then associates with importin beta and the nuclear pore complex to transfer the T-DNA into the nucleus. So that the T-DNA can integrate into the host genome.
We inoculate Agrobacterium containing our genes of interest, onto wounded plant tissue explants. The Agrobacterium then transfers the gene of interest into the DNA of the plant tissue.
Introduction
Ti plasmid
Agrobacterium tumefaciens
Ti plasmid structure
Overview of infection process
Ti plasmid derived vector systems
Cointegrate vectors
Binary vectors
Agrobacterium mediated transformation of explants
Conclusions
References
Genetic manipulation of plant and animal cells have to be confirmed for further application. One such confirmatory method is the use of stains/dyes which produces fluorescence when the recombination is successful.
Presented by- MD JAKIR HOSSAIN
Doctoral Research Scholar
Department of Agricultural Genetic Engineering ,
Faculty of Agricultural Sciences and Technologies,
Nigde Omer Halisdemir University, Turkey
E. Mail- mjakirbotru@gmail.com
Somaclonal Variation in Plant tissue culture - Variation in somaclones (somatic cells of plants)
Somaclonal variation # Basis of somaclonal variation # General feature of Somaclonal variations # Types and causes of somaclonal variation # Isolation procedure of somaclones via without in-vitro method and with in-vitro method with their limitations and advantages # Detection of isolated somaclonal variation # Application (with examples respectively related to crop improvement) # Advantages and disadvantages of somaclonal variations.
https://www.youtube.com/watch?v=IZwrkgADM3I
Also watch, Gametoclonal variation slides to understand, how to changes occur in gametoclones of plants.
https://www.slideshare.net/SharmasClasses/gametoclonal-variation
What are an expression vector? Detailed description of plant gene structure. Plant expression vector systems are generally consists of Ri and Ti plasmids.
The other vectors which are generally used are DNA and RNA viruses.
Genetic manipulation of plant and animal cells have to be confirmed for further application. One such confirmatory method is the use of stains/dyes which produces fluorescence when the recombination is successful.
Presented by- MD JAKIR HOSSAIN
Doctoral Research Scholar
Department of Agricultural Genetic Engineering ,
Faculty of Agricultural Sciences and Technologies,
Nigde Omer Halisdemir University, Turkey
E. Mail- mjakirbotru@gmail.com
Somaclonal Variation in Plant tissue culture - Variation in somaclones (somatic cells of plants)
Somaclonal variation # Basis of somaclonal variation # General feature of Somaclonal variations # Types and causes of somaclonal variation # Isolation procedure of somaclones via without in-vitro method and with in-vitro method with their limitations and advantages # Detection of isolated somaclonal variation # Application (with examples respectively related to crop improvement) # Advantages and disadvantages of somaclonal variations.
https://www.youtube.com/watch?v=IZwrkgADM3I
Also watch, Gametoclonal variation slides to understand, how to changes occur in gametoclones of plants.
https://www.slideshare.net/SharmasClasses/gametoclonal-variation
What are an expression vector? Detailed description of plant gene structure. Plant expression vector systems are generally consists of Ri and Ti plasmids.
The other vectors which are generally used are DNA and RNA viruses.
Introduction to plant biotechnology part 2Somnath Mondal
In part 1 we went through restriction enzymes and plasmid vector construct. Here in part 2, we will go through the bio-data of Agrobacterium tumefaciens and what properties make it natural plant genetic engineer!
Various virus vector related to Plant and Animal for gene cloning and transfo...PrabhatSingh628463
Various virus vector related to Plant and Animal for gene cloning and transformation and Expression vector and it’s mode of expression in plant and animal cells
Agrobacterium mediated gene transfer in plants.ICHHA PURAK
This power point presentation consist of 41 slides. Attempts have been made to illustrate how Agrobacterium behaves us natural genetic engineer. How it can infect a plant through wound and a part of DNA present on Ti plasmid is Tranferred and causes disease as crown gall in the infected plant. In second part of the presentation attempts have been made to describe how Agrobacterium can be utilized for iinsertion of desired gene into the plant,what manipulation are to be made with Agrobacterium.How infection and transfer of desired gene can be made possible.What is the role of plant tissue culture etc.
Agrobacterium mediated gene transfer - LIKE NEVER BEFORE!!Shovan Das
Methods of gene transfer, about agrobacterium, about Ti-plasmid, about Ri-plasmid, preparation of vectors - co-integrated and binary, gene transfer process.
Agrobacterium mediated gene transfer, Ti-plasmid, cloning vectors based on Ti-plasmid, advantages disadvantages regarding cloning vectors based on Ti-plasmid are major areas covered in this Presentation.
This bacterium has a large plasmid that induces tumor, and for this reason, it was named tumor-inducing (Ti) plasmid.
This is process of altering the genetic makeup of an organism using Recombinant DNA Technology.
The increased availability of biomedical data, particularly in the public domain, offers the opportunity to better understand human health and to develop effective therapeutics for a wide range of unmet medical needs. However, data scientists remain stymied by the fact that data remain hard to find and to productively reuse because data and their metadata i) are wholly inaccessible, ii) are in non-standard or incompatible representations, iii) do not conform to community standards, and iv) have unclear or highly restricted terms and conditions that preclude legitimate reuse. These limitations require a rethink on data can be made machine and AI-ready - the key motivation behind the FAIR Guiding Principles. Concurrently, while recent efforts have explored the use of deep learning to fuse disparate data into predictive models for a wide range of biomedical applications, these models often fail even when the correct answer is already known, and fail to explain individual predictions in terms that data scientists can appreciate. These limitations suggest that new methods to produce practical artificial intelligence are still needed.
In this talk, I will discuss our work in (1) building an integrative knowledge infrastructure to prepare FAIR and "AI-ready" data and services along with (2) neurosymbolic AI methods to improve the quality of predictions and to generate plausible explanations. Attention is given to standards, platforms, and methods to wrangle knowledge into simple, but effective semantic and latent representations, and to make these available into standards-compliant and discoverable interfaces that can be used in model building, validation, and explanation. Our work, and those of others in the field, creates a baseline for building trustworthy and easy to deploy AI models in biomedicine.
Bio
Dr. Michel Dumontier is the Distinguished Professor of Data Science at Maastricht University, founder and executive director of the Institute of Data Science, and co-founder of the FAIR (Findable, Accessible, Interoperable and Reusable) data principles. His research explores socio-technological approaches for responsible discovery science, which includes collaborative multi-modal knowledge graphs, privacy-preserving distributed data mining, and AI methods for drug discovery and personalized medicine. His work is supported through the Dutch National Research Agenda, the Netherlands Organisation for Scientific Research, Horizon Europe, the European Open Science Cloud, the US National Institutes of Health, and a Marie-Curie Innovative Training Network. He is the editor-in-chief for the journal Data Science and is internationally recognized for his contributions in bioinformatics, biomedical informatics, and semantic technologies including ontologies and linked data.
Slide 1: Title Slide
Extrachromosomal Inheritance
Slide 2: Introduction to Extrachromosomal Inheritance
Definition: Extrachromosomal inheritance refers to the transmission of genetic material that is not found within the nucleus.
Key Components: Involves genes located in mitochondria, chloroplasts, and plasmids.
Slide 3: Mitochondrial Inheritance
Mitochondria: Organelles responsible for energy production.
Mitochondrial DNA (mtDNA): Circular DNA molecule found in mitochondria.
Inheritance Pattern: Maternally inherited, meaning it is passed from mothers to all their offspring.
Diseases: Examples include Leber’s hereditary optic neuropathy (LHON) and mitochondrial myopathy.
Slide 4: Chloroplast Inheritance
Chloroplasts: Organelles responsible for photosynthesis in plants.
Chloroplast DNA (cpDNA): Circular DNA molecule found in chloroplasts.
Inheritance Pattern: Often maternally inherited in most plants, but can vary in some species.
Examples: Variegation in plants, where leaf color patterns are determined by chloroplast DNA.
Slide 5: Plasmid Inheritance
Plasmids: Small, circular DNA molecules found in bacteria and some eukaryotes.
Features: Can carry antibiotic resistance genes and can be transferred between cells through processes like conjugation.
Significance: Important in biotechnology for gene cloning and genetic engineering.
Slide 6: Mechanisms of Extrachromosomal Inheritance
Non-Mendelian Patterns: Do not follow Mendel’s laws of inheritance.
Cytoplasmic Segregation: During cell division, organelles like mitochondria and chloroplasts are randomly distributed to daughter cells.
Heteroplasmy: Presence of more than one type of organellar genome within a cell, leading to variation in expression.
Slide 7: Examples of Extrachromosomal Inheritance
Four O’clock Plant (Mirabilis jalapa): Shows variegated leaves due to different cpDNA in leaf cells.
Petite Mutants in Yeast: Result from mutations in mitochondrial DNA affecting respiration.
Slide 8: Importance of Extrachromosomal Inheritance
Evolution: Provides insight into the evolution of eukaryotic cells.
Medicine: Understanding mitochondrial inheritance helps in diagnosing and treating mitochondrial diseases.
Agriculture: Chloroplast inheritance can be used in plant breeding and genetic modification.
Slide 9: Recent Research and Advances
Gene Editing: Techniques like CRISPR-Cas9 are being used to edit mitochondrial and chloroplast DNA.
Therapies: Development of mitochondrial replacement therapy (MRT) for preventing mitochondrial diseases.
Slide 10: Conclusion
Summary: Extrachromosomal inheritance involves the transmission of genetic material outside the nucleus and plays a crucial role in genetics, medicine, and biotechnology.
Future Directions: Continued research and technological advancements hold promise for new treatments and applications.
Slide 11: Questions and Discussion
Invite Audience: Open the floor for any questions or further discussion on the topic.
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
Richard's entangled aventures in wonderlandRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
Intravital microscopy (IVM) is a powerful tool utilized to study cellular behavior over time and space in vivo. Much of our understanding of cell biology has been accomplished using various in vitro and ex vivo methods; however, these studies do not necessarily reflect the natural dynamics of biological processes. Unlike traditional cell culture or fixed tissue imaging, IVM allows for the ultra-fast high-resolution imaging of cellular processes over time and space and were studied in its natural environment. Real-time visualization of biological processes in the context of an intact organism helps maintain physiological relevance and provide insights into the progression of disease, response to treatments or developmental processes.
In this webinar we give an overview of advanced applications of the IVM system in preclinical research. IVIM technology is a provider of all-in-one intravital microscopy systems and solutions optimized for in vivo imaging of live animal models at sub-micron resolution. The system’s unique features and user-friendly software enables researchers to probe fast dynamic biological processes such as immune cell tracking, cell-cell interaction as well as vascularization and tumor metastasis with exceptional detail. This webinar will also give an overview of IVM being utilized in drug development, offering a view into the intricate interaction between drugs/nanoparticles and tissues in vivo and allows for the evaluation of therapeutic intervention in a variety of tissues and organs. This interdisciplinary collaboration continues to drive the advancements of novel therapeutic strategies.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
2. • Agrobacterium is a rod shaped plant pathogenic soil
bacteria having two strains.
• A. tumifaciens cause crown gall (tumor) and
A. rhizogenes cause hairy root disease in dicot plants by
infecting through wounds on roots or stem at the soil
surface.
Agrobacterium
3. • The bacterium contains Ti (Tumor inducing ) and Ri (Root
inducing) plasmids. Both these plasmids can transfer
part of their DNA (T-DNA) into plant cell chromosome by
which Plant cells become transformed by expression of
T-DNA gene which induce disease.
Ti plasmid
4. COMPONENTS OF Ti PLASMID
• T- (Transferable) DNA region
• Vir (Virulence ) region
• Host Specificity Region
• Ori (origin of Replication) region
The Ti plasmids are classified into different ( about 14)
types depending upon the specific opine being synthesized.
( octapine/nopaline/Agropine ).
5.
6. • It is ~200 kb mega plasmid.
• T-DNA ( 15-40 kb) region contains genes for synthesis of
Auxins, Cytokinin and Opines.
• Auxins and cytokinin genes are expressed in plant tissue
inducing disease.
• Opines (unusual amino acids ) produced by infected cells
are used as nutrients by Agrobacterium.
• T-DNA region is bordered on both sides by 25bp repeat
which helps in its transfer to plant genome.
7. • Virulence Region contains about 8 operons having about
24- 25 genes
• These genes help in transfer of T-DNA.
• Host specificity region has gene for conjugative transfer
and opine catabolism.
• Ti plasmid also has origin of replication.
8. ORGANISATION OF T-DNA
• T-DNA is ~ 23kb ( 15-40kb) segment bordered on both
sides by 25bp direct repeat sequences.
• T-DNA contains genes for tumor induction (IAAM, IAAH &
IPT) by forming auxins, cytokinins and Opines.
• All the genes in T-DNA region contain eukaryotic
regulatory sequences, so are expressed only in plant
cells.
9. ORGANISATION OF Vir REGION
• Vir region contains 8 operons (VirA,B,C,D,E,F ,G &H) which
together have 25 genes.
• Vir region mediates transfer of T-DNA into plant genome. It is
itself not transferred.
• VirA and Vir G are constitutive operons encoding Vir A and VirG
Proteins.
• Other Vir operons encode various proteins involved in T-DNA
transfer.
10. Gene/Operon Function
T-DNA
iaaM (auxL tins I)*
Auxin biosynthesis; encodes enzyme tryptophan-2-mono-oxygenase, which
converts tryptophan into indole-3-acctamide (IAM).
iaaH (aux2, tms2)
Auxin biosynthesis; encodes enzyme indole-3-acetamide hydrolase, which
converts IAM into IAA (indole-3-acetic acid).
ipt (tmr, Cyt )
Cytokinin biosynthesis; encodes enzyme isopentenyl transferase, which catalyzes
the formation of isopentenyl adenine.
Nos
Nopaline biosynthesis; encodes the enzyme nopaline synthase, which produces
nopaline from arginine and pyruvic acid.
24 bp left and right border
sequences
Site of endonuclease action duringT-DNA transfer; the onlysequences of T-DNA
essential for its transfer.
vir Region
vir A(1)
Encodes a receptor for acetosyringone that functions as an autokinase; also
phosphorylates VirG protein; constitutive expression.
virB (11)
Membrane proteins; possibly form a channel for T-DNA transport (conjugal tube
formation); VirB 11 has ATPase activity.
virC (2)
Helicase; binds to the overdrive region just outside the right border; involved in
unwinding of T-DNA.
virD(4)
VirDl has topoisomerase activity; it binds to the right border of T-DNA; VirD2 is
an endonuclease; it nicks the right border.
virE (2) Single-strand binding proteins (SSBP); bind to T-DNA during its transfer.
virF(l)
virG (l)
DNA binding protein; probably forms dimer after phosphorylation by VirA, and
induces the expression of all vir operons; constitutive expression.
virH (2) Not well known.
11. MECHANISM OF TRANSFER OF T-DNA
• Transfer of T-DNA is a step wise process.
• Vir region of Ti plasmid becomes activated by the phenolic
signal molecules Acetosyringone and α-
hydroxyacetosyringone released by wounded tissue of dicot
plants which constitute wound response.
12. • Acetosyringone and α-hydroxyacetosyringone bind with Vir
A protein (located in the inner membrane) and activates it.
It start functioning as autokinase to phosphorylate itself
by ATP. Phosphorylated Vir A protein then phosphorylates
Vir G protein which then dimerises.
• Phosphorylated Vir G protein has DNA binding function. It
induces expression of rest of Vir operons.
• Vir D1 protein has topoisomerase and endonuclease
activity. It binds to right border sequence of T-DNA and
facilitate the action of Vir D2 protein which is also
endonuclease and nicks at the right border and remains
bound to 5’end.
13.
14. • The 3’end produced at the site of nick serves as a primer for DNA
synthesis in 5’----3’ direction as a result of which one strand of T-
DNA is displaced from the DNA duplex.
• The T-DNA strand is again nicked at the left border to generate a
single strand copy of T-DNA.
• To this single strand copy Vir E 2 protein (single strand DNA
binding proteins ) bind for its protection against exonucleases.
• Vir B operon consisting of 11 genes encode membrane bound Vir
B proteins. These along with Vir D4 proteins participate in
conjugal tube formation between bacterial and plant cells for
transfer of T-DNA.
• Vir D2 which remains bound to 5’end of T DNA has a signal
sequence which drives it into the nucleus of plant cell.
15.
16. INTEGRATION OF T-DNA INTO PLANT GENOME
• T-DNA enters plant cell as a single stranded structure which is
immediately converted into double stranded form.
• Vir E2 also has nuclear localization sequence and is
responsible for transfer of T DNA into plant cell nucleus.
• Double stranded T-DNA integrate at random sites in the host
plant genome.
• For integration 23-79 base pair deletion takes place at the
integration or target site.
• After integration of T-DNA into plant genome ,the genes for
auxins, cytokinins and opines express themselves which result
in uncontrolled growth in the form of tumor.