Question1: There are five ethylene receptors present in this plant. Ethylene is

Question

Question1: There are five ethylene receptors present in this plant. Ethylene is a gaseous hormone that controls various aspects of plant growth and physiology including response to some types of stress, fruit ipening. 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) ABSENCE OF ETHYLENE (B) PRESENCE OF ETHYLENE inactive ethylene receptor active ethylene receptor CYTOSOL ER membrane active protein kinase inactive protein kinase 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) a. Do you think ethylene works across long or short distances? Explain why. What might lead to the different physiological responses (fruit ripening, flower fading, leaf senescence) in response to ethylene? b. Would you predict that the timing of the response to ethylene occurs on a long- or short-term basis? Explain why. c.

Explanation / Answer

a. Ethylene works across long distances.
The transcription factors activated by ethylene can cause effects on tissues that are located elsewhere.

b. Different downstream factors activated/repressed by ethylene signaling turn on/off different metabolic pathways.

c. The timing of response to ethylene occurs on a short time basis. The binding of ethylene to the receptor and downstream signaling can occur very swiftly.

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