Signal Transduction in plants: the role of phytochrome in the de-etiolation (greening) response
CYTOPLASM
Reception
Plasma
membrane
Cell
wall
Phytochrome
activated
by light
Light
Transduction
Second messenger
produced
cGMP
Specific
protein
kinase 1
activated
NUCLEUS
1
2
Specific
protein
kinase 2
activated
Ca2+ channel
opened
Ca2+
Slide 9
Signal Transduction in plants: the role of phytochrome in the de-etiolation (greening) response
CYTOPLASM
Reception
Plasma
membrane
Cell
wall
Phytochrome
activated
by light
Light
Transduction
Second messenger
produced
cGMP
Specific
protein
kinase 1
activated
NUCLEUS
1
2
Specific
protein
kinase 2
activated
Ca2+ channel
opened
Ca2+
Response
3
Transcription
factor 1
Transcription
factor 2
NUCLEUS
Transcription
Translation
De-etiolation
(greening)
response
proteins
P
P
Slide 10
Response - A signal transduction pathway leads to regulation of one or more cellular activities.
In most cases, these responses to stimulation involve increased activity of enzymes.
This can occur by transcriptional regulation or post-translational modification.
Slide 11
Transcriptional Regulation
Specific transcription factors bind directly to specific regions of DNA and control transcription of genes.
Positive transcription factors are proteins that increase the transcription of specific genes, while negative transcription factors are proteins that decrease the transcription of specific genes.
Slide 12
Post-Translational Modification of Proteins
Post-translational modification involves modification of existing proteins in the signal response.
Modification often involves the phosphorylation of specific amino acids.
Slide 13
De-Etiolation (“Greening”) Proteins
Many enzymes that function in certain signal responses are directly involved in photosynthesis.
Other enzymes are involved in supplying chemical precursors for chlorophyll production.
Slide 14
Hormones are chemical signals that coordinate different parts of an organism.
Any response resulting in curvature of organs toward or away from a stimulus is called a tropism = a growth response.