Stimulation of the blue light phototropic receptor NPH1 causes a transient increase in cytosolic Ca2+.
Blue light regulates plant growth and development, and three photoreceptors, CRY1, CRY2, and NPH1, have been identified. The transduction pathways of these receptors are poorly understood. Transgenic plants containing aequorin have been used to dissect the involvement of these three receptors in the regulation of intracellular Ca2+. Pulses of blue light induce cytosolic Ca2+ transients lasting about 80 s in Arabidopsis and tobacco seedlings. Use of organelle-targeted aequorins shows that Ca2+ increases are limited to the cytoplasm. Blue light treatment of cry1, cry2, and nph1 mutants showed that NPH1, which regulates phototropism, is largely responsible for the Ca2+ transient. The spectral response of the Ca2+ transient is similar to that of phototropism, supporting NPH1 involvement. Furthermore, known interactions between red and blue light and between successive blue light pulses on phototropic sensitivity are mirrored in the blue light control of cytosolic Ca2+ in these seedlings. Our observations raise the possibility that physiological responses regulated by NPH1, such as phototropism, may be transduced through cytosolic Ca2+.
Baum
G
G
Institute of Cell and Molecular Biology, University of Edinburgh, United Kingdom.
Long
J C
JC
Jenkins
G I
GI
Trewavas
A J
AJ
D000331:Aequorin; D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D029681:Arabidopsis Proteins; D002118:Calcium / Q000378:metabolism*; D056931:Cryptochromes; D003593:Cytoplasm / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism*; D029721:Drosophila Proteins; D005136:Eye Proteins; D005420:Flavoproteins / Q000235:genetics / Q000528:radiation effects; D008027:Light; D008163:Luminescent Measurements; D009154:Mutation; D010750:Phosphoproteins / Q000235:genetics / Q000528:radiation effects*; D017956:Photoreceptor Cells, Invertebrate; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism / Q000528:radiation effects; D018524:Phototropism / Q000528:radiation effects; D010947:Plants, Toxic; D017346:Protein Serine-Threonine Kinases; D043562:Receptors, G-Protein-Coupled; D015398:Signal Transduction / Q000502:physiology / Q000528:radiation effects; D014026:Nicotiana / Q000166:cytology / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects
D029681:Arabidopsis Proteins; C538962:CRY1 protein, Arabidopsis; D056931:Cryptochromes; D029721:Drosophila Proteins; D005136:Eye Proteins; D005420:Flavoproteins; D010750:Phosphoproteins; D045322:Photosynthetic Reaction Center Complex Proteins; D043562:Receptors, G-Protein-Coupled; C119828:cry protein, Drosophila; D000331:Aequorin; C103646:NPH1 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases; D002118:Calcium