Plant Pathology: Opines in Crown Galls

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Questions and Answers

What determines the type of opine found in crown galls?

The environmental conditions

The plant species

The size of the tumor

The bacterium (correct)

Nopaline strains contain two T-DNA regions of different sizes.

False

What are the two types of opine mentioned in the content?

Nopaline and Octopine

The bacteria used in the study is called __________.

Agrobacterium tumefaciens Signup and view all the answers

Match the following strains with their respective opine:

Octopine-utilizing strain = Octopine Nopaline-utilizing strain = Nopaline Signup and view all the answers

What is the main function of VirA?

Senses plant phenolic compounds Signup and view all the answers

Viable bacteria are no longer necessary for tumor growth beyond how many days post-inoculation?

Two days Signup and view all the answers

VirB is responsible for processing T-DNA in the plant nucleus.

False Signup and view all the answers

Tumors can form if the tissue is incubated at room temperature for at least one day before heat-killing the bacteria.

False Signup and view all the answers

What was the temperature used to kill the bacteria in the experiments?

47°C Signup and view all the answers

Which Vir gene is involved in cutting the T-DNA at the borders?

VirD2 Signup and view all the answers

VirF is thought to degrade host cell factors during ______.

infection Signup and view all the answers

Match the following Vir genes with their functions:

VirA = Senses plant phenolic compounds VirB = Forms the T-pilus for substrate transfer VirD2 = Cuts T-DNA at the borders VirE2 = Binds to T-DNA Signup and view all the answers

What triggers the induction of vir genes in Agrobacterium?

Presence of sugars and phenolics Signup and view all the answers

The T-DNA transferred to the plant cell is a double-stranded molecule.

False Signup and view all the answers

What are the two main border regions flanking the T-DNA in Agrobacterium?

Left Border (LB) and Right Border (RB) Signup and view all the answers

What is the primary purpose of Agrobacterium tumefaciens in plant cells?

To reprogram plant cells to divide and produce opines Signup and view all the answers

During T-DNA processing, the _____ protein is responsible for auto-phosphorylation.

VirA Signup and view all the answers

Match the following Agrobacterium components with their roles:

VirA = Signal detection and transduction VirG = Regulation of virulence gene expression Ti Plasmid = Carries T-DNA and virulence genes T-DNA = Integrates into the host genome Signup and view all the answers

Agrobacterium tumefaciens can transform fungi, but not non-plant species.

False Signup and view all the answers

What two virulence loci on the Ti plasmid are mentioned as determining the range of plant species that can be transformed?

virC and virF Signup and view all the answers

The dominant selection marker system widely used in fungi is the _____ gene, which confers resistance to hygromycin.

hygromycin phosphotransferase Signup and view all the answers

Match the following terms with their descriptions:

Agrobacterium tumefaciens = Natural plant pathogen that transfers DNA to plant cells Opines = Chemicals produced by transformed plant cells Saccharomyces cerevisiae = A commonly transformed fungal species using ATMT hygromycin phosphotransferase = Gene that provides antibiotic resistance in fungi Signup and view all the answers

Which gene is commonly associated with kanamycin resistance in plant systems?

neomycin phosphotransferase (NPTII) Signup and view all the answers

Plant-active selectable marker genes are typically associated with herbicide resistance only.

False Signup and view all the answers

What is the function of the CaMV-35S promoter in plant transformation?

To control the expression of transgenes Signup and view all the answers

The ____ gene is used as a reporter system in plant transformation, allowing for detection of transformed tissues.

GUS Signup and view all the answers

Match the following elements with their correct descriptions:

NPTII = Gene for kanamycin resistance HPT = Gene for hygromycin resistance GUS = Reporter for gene expression GFP = Fluorescent protein used as a reporter Signup and view all the answers

What is typically used as a carbon source to eliminate E.coli from Agrobacterium cultures?

Sucrose Signup and view all the answers

The transient expression of T-DNA can occur within the first 12 hours after agroinfiltration.

True Signup and view all the answers

What is one primary characteristic of T-DNA Binary vectors?

Contains left and right border repeat sequences Signup and view all the answers

Study Notes

Opines and Crown Galls

Opines are specialized compounds produced in crown galls, a result of Agrobacterium tumefaciens infection.
The type of opine produced is dictated by the specific strain of bacterium, with notable examples being octopine and nopaline.

T-DNA Characteristics

Nopaline strains feature a single T-DNA region, approximately 20kb in size.
Octopine strains contain two T-DNA regions (T1 and TR), sized around 14kb and 17kb, respectively.

Tumor Independence

Tumors can become independent from the bacteria a few days post-inoculation, as bacteria alter host cells by transferring DNA.
A lag exists between infection and tumor growth, as demonstrated by experiments with inoculated periwinkle stems.

Agrobacterium Gene Transfer

Agrobacterium tumefaciens transfers DNA into plant cell genomes, prompting cells to divide and produce opines for bacterial sustenance.
Virulence (vir) loci on the Ti plasmid, such as virC and virF, impact the range of plant species that can develop crown gall tumors.

Agrobacterium-Mediated Transformation in Fungi

In 1995, successful transformation of Saccharomyces cerevisiae using Agrobacterium tumefaciens-mediated transformation (ATMT) was reported.
More than 125 fungal species have been transformed, often using the hygromycin phosphotransferase gene as a selection marker.

Broad Host Range of ATMT

Agrobacterium tumefaciens can transform a wide range of plant species, including monocots and dicots, as well as non-host organisms like fungi and algae.
It facilitates both transient and stable transformation methods in plants.

Virulence Genes (Vir Genes)

VirA: Senses plant phenolic compounds induced by wounding.
VirG: Functions as a cytoplasmic response element for transcription of other vir genes.
VirB: Comprises 11 proteins essential for T-DNA substrate transfer and T-pilus formation.
VirD: Processes T-DNA through five genes, with virD2 acting as an endonuclease/integrase.
VirE: Includes virE1 (chaperone) and virE2 (forms channels in membranes for T-DNA).
VirF: Aids in the breakdown of host cell factors during infection and assists T-DNA release.

T-DNA Integration Process

The T-strand, a single-stranded molecule, is transferred into the plant cell, rather than a double-stranded DNA molecule.
VirA activates VirG, leading to the induction of other vir genes in the presence of phenolic signals.

Marker Genes and Reporter Systems in Plants

Selection markers like neomycin phosphotransferase (NPTII) and hygromycin phosphotransferase (HPT) are utilized for resistance.
Reporter systems include β-D-glucuronidase (GUS), various luciferases (LUC), and green fluorescent protein (GFP).

Characteristics of T-DNA Binary Vectors

Include left and right border repeat sequences to ensure only T-DNA is integrated.
Contain plant-active selectable marker genes, typically for antibiotic or herbicide resistance.
Feature restriction sites for gene-of-interest insertion and origins of replication for maintenance in both E. coli and Agrobacterium.

Transient Transformation

Non-integrated T-DNA can persist in the nucleus, allowing transient gene expression.
Expression of transgenes can occur within 3–5 days post-inoculation, often reaching high levels within 2-4 days in species like lettuce and tobacco.

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Description

Explore the fascinating world of plant pathology with a focus on opines found in crown galls. This quiz dives into the types of opines and their significance in plant biology. Test your knowledge and deepen your understanding of plant diseases.