Podcast
Questions and Answers
What role does GA play in plant growth?
What role does GA play in plant growth?
- It restricts seed germination.
- It eliminates the need for cyclins.
- It promotes elongation by stabilizing microtubules. (correct)
- It inhibits cell expansion.
In pea plants, how can a mutant na shoot be rescued?
In pea plants, how can a mutant na shoot be rescued?
- By applying gibberellins directly.
- By grafting onto a Na root. (correct)
- By growing in isolation.
- By treating with auxins.
During the germination of monocot seeds, where does GA move after the embryo?
During the germination of monocot seeds, where does GA move after the embryo?
- To the stigma.
- To the root.
- To the aleurone. (correct)
- To the cotyledon.
What does GA induce to promote cell division?
What does GA induce to promote cell division?
Which of the following is true about GA transport?
Which of the following is true about GA transport?
Which process is directly activated by GA during seed germination?
Which process is directly activated by GA during seed germination?
What effect does GA have on cortical microtubules?
What effect does GA have on cortical microtubules?
How does GA contribute to cell expansion?
How does GA contribute to cell expansion?
What is the primary function of GA receptors as described in the content?
What is the primary function of GA receptors as described in the content?
What characteristic is unique to the gid1 rice mutant?
What characteristic is unique to the gid1 rice mutant?
What effect does overexpression of GID1 have on plants?
What effect does overexpression of GID1 have on plants?
How many GID1 genes does Arabidopsis contain?
How many GID1 genes does Arabidopsis contain?
What is the phenotype of gid1a gid1b gid1c triple mutants in terms of growth and response to GA?
What is the phenotype of gid1a gid1b gid1c triple mutants in terms of growth and response to GA?
What type of family do GA receptors belong to?
What type of family do GA receptors belong to?
What was the original publication that identified GID1 and its role?
What was the original publication that identified GID1 and its role?
What is a common feature of single GID1 receptor mutants in Arabidopsis?
What is a common feature of single GID1 receptor mutants in Arabidopsis?
What is the primary role of F-box proteins SLEEPY (SLY) and GID2 in plant growth?
What is the primary role of F-box proteins SLEEPY (SLY) and GID2 in plant growth?
What effect do sleepy and gid2 mutants have on DELLA protein levels in response to gibberellins (GA)?
What effect do sleepy and gid2 mutants have on DELLA protein levels in response to gibberellins (GA)?
How would you describe the phenotype of the gid2 mutant?
How would you describe the phenotype of the gid2 mutant?
What is the function of the slr1 gene in rice plants?
What is the function of the slr1 gene in rice plants?
What happens to plant growth when both SLEEPY and GID2 are inactive in a plant?
What happens to plant growth when both SLEEPY and GID2 are inactive in a plant?
What does the phenotype of a slr1gid2 double mutant most likely exhibit?
What does the phenotype of a slr1gid2 double mutant most likely exhibit?
The accumulation of which protein is primarily affected in sleepy1-10 and gid2-1 mutants under GA treatment?
The accumulation of which protein is primarily affected in sleepy1-10 and gid2-1 mutants under GA treatment?
Which of the following statements is true regarding the function of SLEEPY in Arabidopsis?
Which of the following statements is true regarding the function of SLEEPY in Arabidopsis?
How many DELLA proteins does Arabidopsis have?
How many DELLA proteins does Arabidopsis have?
Which DELLA protein is unique to rice?
Which DELLA protein is unique to rice?
What type of function do RGA, RGL2, and RGL3 have in Arabidopsis?
What type of function do RGA, RGL2, and RGL3 have in Arabidopsis?
Which process affects the post-translational regulation of DELLA proteins?
Which process affects the post-translational regulation of DELLA proteins?
Which of the following is the DELLA protein in barley?
Which of the following is the DELLA protein in barley?
Which mutation leads to constitutive GA responses in Arabidopsis?
Which mutation leads to constitutive GA responses in Arabidopsis?
What do RGA and GAI have in common regarding their transcription?
What do RGA and GAI have in common regarding their transcription?
Which DELLA protein is responsible for increased height in wheat?
Which DELLA protein is responsible for increased height in wheat?
Which modification is NOT associated with DELLA protein regulation?
Which modification is NOT associated with DELLA protein regulation?
What is a common function of DELLA proteins in plants?
What is a common function of DELLA proteins in plants?
What is the role of DELLA proteins in the gibberellin signaling pathway?
What is the role of DELLA proteins in the gibberellin signaling pathway?
What happens in plants with a loss of DELLA repressors when exposed to gibberellin?
What happens in plants with a loss of DELLA repressors when exposed to gibberellin?
What is a characteristic of the gai mutation in Arabidopsis?
What is a characteristic of the gai mutation in Arabidopsis?
What function does the 26S proteasome serve in relation to ubiquitinated proteins?
What function does the 26S proteasome serve in relation to ubiquitinated proteins?
What is the consequence of enhanced DELLA repressor activity in the presence of gibberellin?
What is the consequence of enhanced DELLA repressor activity in the presence of gibberellin?
Study Notes
GA Biosynthesis and Regulation
- Gibberellins (GAs) are regulated by various hormones and environmental factors.
- GAs can move over long distances and are graft-transmissible, influencing nearby plants.
- In peas, a dwarf mutant can be rescued through grafting onto a wild-type rootstock.
- In maize, GA or a precursor transfers from wild-type plants to dwarf mutants, promoting their growth.
GA Transport and Action in Seed Germination
- During seed germination in monocots, GAs move from the embryo to the aleurone layer to activate amylase, converting starch to sugars.
- GA promotes plant growth primarily through cell expansion and division.
Mechanism of GA-Induced Growth
- GAs induce cell division via cyclins, important regulatory proteins of the cell cycle.
- Cell elongation is facilitated by GA's effects on cell wall loosening and stabilization of cortical microtubules.
DELLA Proteins and Their Functions
- Different plants exhibit varying numbers of DELLA proteins; Arabidopsis has five.
- In Arabidopsis, DELLA proteins (GAI, RGA, RGL1, RGL2, RGL3) play distinct roles in regulating seed germination, stem elongation, and floral development.
- DELLA protein regulation occurs transcriptionally and post-translationally, with GA signaling leading to their degradation.
GA Receptors and Their Role
- GA receptors, part of the serine hydrolase family, do not have enzymatic activity.
- GID1, first identified in rice, acts as a GA receptor; its mutants are gibberellin-insensitive.
- Overexpression of GID1 enhances plant sensitivity to GAs, increasing growth responses.
Functional Redundancy of GID1 in Arabidopsis
- Arabidopsis possesses three GID1 genes; these show redundancy, with single mutants revealing minimal phenotypic changes.
- Triple mutants of GID1 display severe dwarfism and lack GA responses.
SLEEPY/GID2 and DELLA Interaction
- F-box proteins SLEEPY (SLY) in Arabidopsis and GID2 in rice bind to DELLA proteins for proteolytic degradation.
- Mutants lacking SLEEPY or GID2 demonstrate reduced growth due to the stabilization of DELLA proteins, inhibiting GA-induced elongation.
Dominant and Recessive Mutations in GID and DELLA Proteins
- Mutations in slr1 result in elongated and slender plants due to enhanced GA responses.
- Mutations in gid2 lead to dwarfism as they fail to degrade DELLA proteins, resulting in restricted growth.
- The double mutant of slr1 and gid2 combines traits from both, amplifying the GA response due to loss of DELLA repression.
Proteolytic Pathway Involving Ubiquitin
- Ubiquitin ligase complexes target proteins for degradation, essential for regulating protein levels in response to GA.
- The 26S proteasome is responsible for breaking down the ubiquitinated proteins, recycling ubiquitin for future use.
Summary of GA's Role
- GAs interact with a complex regulatory network involving DELLA proteins and GID1 receptors to promote growth.
- Understanding the balance of these factors is critical for manipulating plant growth and development in agricultural practices.
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Description
Explore the complex regulatory control of gibberellins (GAs) in plant biosynthesis and metabolism. This quiz examines the movement of GAs, their graft-transmissibility, and the physiological effects of grafting on mutant plants like peas and maize seedlings.
