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What does the phloem sap predominantly contain?
What does the phloem sap predominantly contain?
What effect do the ipt1;3;5;7 mutants have on stem growth?
What effect do the ipt1;3;5;7 mutants have on stem growth?
What is synthesized at high levels in the roots by CYP735A?
What is synthesized at high levels in the roots by CYP735A?
How can the phenotype of ipt1;3;5;7 mutants be rescued?
How can the phenotype of ipt1;3;5;7 mutants be rescued?
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What role do cytokinins (CKs) have in plants?
What role do cytokinins (CKs) have in plants?
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What is the primary function of HPTs in plants?
What is the primary function of HPTs in plants?
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What does the loss-of-function of one or two AHPs indicate about their role in cytokinin signaling?
What does the loss-of-function of one or two AHPs indicate about their role in cytokinin signaling?
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Which of the following characteristics is associated with the triple mutant of AHPs?
Which of the following characteristics is associated with the triple mutant of AHPs?
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Based on the provided content, how do HPTs and AHPs function in cytokinin signaling?
Based on the provided content, how do HPTs and AHPs function in cytokinin signaling?
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Which protein is primarily mentioned as functioning in the transduction of cytokinin signaling?
Which protein is primarily mentioned as functioning in the transduction of cytokinin signaling?
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What role does the input domain play in bacterial systems?
What role does the input domain play in bacterial systems?
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What mechanism mediates cytokinin signaling in plants?
What mechanism mediates cytokinin signaling in plants?
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In the context of cytokinin signaling, what does HPT stand for?
In the context of cytokinin signaling, what does HPT stand for?
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How many histidine phosphotransfer proteins (HPTs) are mentioned in the context of the Arabidopsis cytokinin response pathway?
How many histidine phosphotransfer proteins (HPTs) are mentioned in the context of the Arabidopsis cytokinin response pathway?
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What type of signal relay is facilitated by the aspartate (D) in the response regulator?
What type of signal relay is facilitated by the aspartate (D) in the response regulator?
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Which components are included in the Arabidopsis cytokinin response pathway?
Which components are included in the Arabidopsis cytokinin response pathway?
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What is the role of hybrid histidine kinases in bacterial signaling?
What is the role of hybrid histidine kinases in bacterial signaling?
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Which of the following response regulators in Arabidopsis are also known as ARRs?
Which of the following response regulators in Arabidopsis are also known as ARRs?
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What is the primary function of AHK4 in Arabidopsis?
What is the primary function of AHK4 in Arabidopsis?
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What is the phenotype observed in cre1 mutants of Arabidopsis?
What is the phenotype observed in cre1 mutants of Arabidopsis?
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How can cytokinin receptor function be assessed experimentally?
How can cytokinin receptor function be assessed experimentally?
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What characterizes the activity of Arabidopsis CK receptors?
What characterizes the activity of Arabidopsis CK receptors?
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What is the primary consequence of the triple mutant phenotype in Arabidopsis?
What is the primary consequence of the triple mutant phenotype in Arabidopsis?
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Which of the following cytokinin receptors is associated with the wooden-leg (wol) mutant?
Which of the following cytokinin receptors is associated with the wooden-leg (wol) mutant?
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What effect does cytokinin have on root growth in Arabidopsis?
What effect does cytokinin have on root growth in Arabidopsis?
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In the context of CK response, what does the ARR6 promoter indicate?
In the context of CK response, what does the ARR6 promoter indicate?
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What disease is primarily caused by Agrobacterium tumefaciens?
What disease is primarily caused by Agrobacterium tumefaciens?
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Which plant hormones are produced as a result of T-DNA transfer from Agrobacterium tumefaciens?
Which plant hormones are produced as a result of T-DNA transfer from Agrobacterium tumefaciens?
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What is the primary role of the tmr gene in Agrobacterium tumefaciens?
What is the primary role of the tmr gene in Agrobacterium tumefaciens?
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What type of plasmids does Agrobacterium tumefaciens carry that contribute to tumor formation?
What type of plasmids does Agrobacterium tumefaciens carry that contribute to tumor formation?
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Which enzyme encoded by the tmr gene is crucial for cytokinin synthesis?
Which enzyme encoded by the tmr gene is crucial for cytokinin synthesis?
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Which statement accurately describes the differences between bacterial IPT genes and plant IPT genes?
Which statement accurately describes the differences between bacterial IPT genes and plant IPT genes?
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What is T-DNA in the context of Agrobacterium tumefaciens?
What is T-DNA in the context of Agrobacterium tumefaciens?
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Which of the following growths is typically associated with the presence of Agrobacterium tumefaciens?
Which of the following growths is typically associated with the presence of Agrobacterium tumefaciens?
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What is the primary consequence of the interaction between Agrobacterium tumefaciens and plant cells?
What is the primary consequence of the interaction between Agrobacterium tumefaciens and plant cells?
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Study Notes
Agrobacterium tumefaciens and Crown Gall Disease
- Agrobacterium tumefaciens causes crown gall disease in plants, characterized by tumor-like growths.
- This bacterium induces the plant to produce auxin and cytokinin, plant hormones that stimulate cell division and growth.
T-DNA Transfer and Tumor Formation
- Agrobacterium tumefaciens carries Ti plasmids, which contain a segment of DNA called T-DNA.
- This T-DNA is transferred into the plant nucleus, integrating into the plant genome.
- The T-DNA includes genes for the biosynthesis of auxin and cytokinin, contributing to tumor formation.
Cytokinin Biosynthesis and the tmr Gene
- The tmr gene, present in T-DNA, encodes isopentenyl transferase, a key enzyme in cytokinin synthesis.
- This enzyme converts AMP into isopentenyladenine (iP), a precursor for various cytokinins.
Cytokinin Translocation and Vascular Cambium Activity
- Cytokinin transport occurs via phloem and xylem, with different cytokinins being transported in each.
- The xylem sap primarily carries trans-zeatin (tZ) and tZ riboside, produced in the roots by CYP735A.
- Cytokinins play a crucial role in vascular cambium activity, contributing to secondary growth.
- Grafting experiments with wild-type and ipt1;3;5;7 mutant plants reveal the long-distance translocation of CKs and their importance for cambial activity.
Cytokinin Signaling Mechanism
- Cytokinin signaling is mediated by a two-component-like system, involving phosphorylation of proteins.
- Receptors (AHKs), histidine phosphotransfer proteins (HPTs/AHPs), and response regulators (ARRs) are key players.
- AHKs perceive cytokinin and autophosphorylate, transferring the phosphate group to HPTs, then to ARRs.
- ARRs are response regulators that activate downstream genes and influence various developmental processes.
Arabidopsis Cytokinin Signaling Pathway
- Arabidopsis possesses three CK receptors: AHK2, AHK3, and AHK4 (identified as the wol and cre1 mutants).
- These receptors act partially redundantly, with the triple mutant exhibiting a complete loss of CK response.
HPTs/AHPs and Response Regulation
- HPTs/AHPs shuttle between the cytoplasm and nucleus, relaying the phosphate signal.
- These proteins are essential for CK signaling but show a degree of redundancy, as loss of one or two AHPs has little effect, while a triple mutant exhibits a short root phenotype characteristic of CK signaling defects.
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Description
Explore the role of Agrobacterium tumefaciens in inducing crown gall disease in plants. This quiz covers the mechanisms of T-DNA transfer, tumor formation, and the significance of cytokinins in plant pathology. Test your understanding of how plant hormones are influenced by this bacterium.
