There are five ethylene receptors present in the model plant organism Arabidposi
ID: 197499 • Letter: T
Question
There are five ethylene receptors present in the model plant organism Arabidposis thaliana. Ethylene is a gaseous hormone that controls various aspects of plant growth and physiology including response to some types of stress, fruit ripening, flower fading, and leaf senescence. The image on the right shows the ethylene signaling pathway in plants. In the absence of ethylene, the receptor directly activates an associated protein kinase, which then indirectly promotes the destruction of a transcription regulator. As a result, ethylene responsive genes remain off. In the presence of ethylene, the receptor and kinase are both inactive, and the transcription regulator remains intact and stimulates transcription of the ethylene-responsive genes.
a.Do you think ethylene works across long or short distances? Explain why.
b.What might lead to the different physiological responses (fruit ripening, flower fading, leaf senescence) in response to ethylene?
c.Would you predict that the timing of the response to ethylene occurs on a long- or short-term basis? Explain why.
d.What is the subcellular localization of the ethylene receptor? Based on this information, what would you predict about the structural properties of ethylene (without looking it up)?
e.We talked about several components of cell-surface receptor-mediated signaling: signal molecule, receptor, intracellular signaling molecules, effector protein, response. Label the applicable components on the ethylene signaling pathway.
(A) ABSENCE OF ETHYLENE (B) PRESENCE OF ETHYLENE active ethylene recepto inactive ethylene ethylene receptor CYTOSOL ER membrane active protein kinase inactive protein kinase transcription regulator active transcription regulator DEGRADATION ETHYLENE-RESPONSIVE GENES OFF TRANSCRIPTION OF ETHYLENE- RESPONSIVE GENES Figure 16-42 Essential Cell Biology, 4th ed. (© Garland Science 2014)Explanation / Answer
A. Long distance - It has a series of reaction to activate the Transcription factor.
B. Ethylene activate expression of ACC synthase or ACC-oxidase which induces Ripening process. Ethylene increases with decrease in concentration of cytokinins and leads to senescence.
C.Time of response is fast. Ethylene emission from fruits is displayed fast changes between anoxic and normal atmospheric condition,
D. Endoplasmic reticulum.
E. Signal molecule - Ethylene
Receptor -- Ethylene receptor
Intracellular signalling - Protein kinase
Effector protein - Transcription regulator
Response - Ethylene responsive genes.
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