Signal transduction pathways in plants
Neuhaus, G., Merkle, T., Rodriguez, M., Köhler, C., Rubiera, R.
Institut für Biologie, Zellbiologie, Universität Freiburg, D-79104 Freiburg, Germany
At least three signal transduction pathways, dependent upon cGMP and/or calcium, are utilized by phytochrome to control the expression of genes required for chloroplast development and anthocyanin biosynthesis in plant cells. Using a soybean photomixotrophic cell culture and microinjection into the cells of a phytochrome-deficient tomato mutant, we have examined the effects of manipulating signal flow through these signaling pathways. We provide evidence that the observed induction and desensitization of chs gene expression in response to light is a result of changes in cGMP levels and, in addition, demonstrate that inter-pathway regulatory mechanisms operate to control the relative outputs from each of the pathways. High activity of the calcium pathway can negatively regulate the cGMP-dependent pathway, and vice versa. The calcium/cGMP-dependent pathway can also be negatively regulated by high activity of the cGMP pathway, because it has a lower threshold requirement for cGMP. In all cases, the molecules that mediate these cross-talk phenomena appear to be downstream components of the signal transduction pathways, rather than calcium and cGMP themselves. Because the same factor appears to both positively regulate one pathway and to negatively regulate another, and vice versa, we propose to call these opposing regulatory mechanisms "reciprocal control." Its importance during plant development is discussed.
| LOCATION |
DATE |
TIME |
| Lecture Hall I |
Monday, April 6 |
03:20 pm |