Cyclic GMP and calcium mediate phytochrome phototransduction.
We have previously used single-cell assays in a phytochrome-deficient tomato mutant to demonstrate that phytochrome signaling involves heterotrimeric G proteins, calcium, and calmodulin. While G protein activation could stimulate full chloroplast development and anthocyanin pigment biosynthesis, calcium and calmodulin could not induce anthocyanins and were only able to stimulate the development of immature chloroplasts lacking cytochrome b6f and photosystem I core components. We now report that cyclic GMP is able to trigger the production of anthocyanins, and that a combination of cyclic GMP with calcium can induce the development of fully mature chloroplasts containing all the photosynthetic machinery. Furthermore, using reporter genes for these different pathways (cab-gus, chs-gus, and fnr-gus) we demonstrate that cGMP and calcium act primarily by modulating gene expression.
Bowler
C
C
Laboratory of Plant Molecular Biology, Rockefeller University, New York, New York 10021-6399.
Neuhaus
G
G
Yamagata
H
H
Chua
N H
NH
D000872:Anthocyanins / Q000378:metabolism; D002118:Calcium / Q000502:physiology*; D002734:Chlorophyll / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism*; D006152:Cyclic GMP / Q000502:physiology*; D003573:Cytochrome b Group / Q000378:metabolism; D045346:Cytochrome b6f Complex; D005786:Gene Expression Regulation; D017343:Genes, Plant; D010834:Phytochrome / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D012273:Ribulose-Bisphosphate Carboxylase / Q000378:metabolism; D015398:Signal Transduction; D013025:Glycine max
D000872:Anthocyanins; D003573:Cytochrome b Group; D012333:RNA, Messenger; D010834:Phytochrome; D002734:Chlorophyll; D045346:Cytochrome b6f Complex; D012273:Ribulose-Bisphosphate Carboxylase; D006152:Cyclic GMP; D002118:Calcium