Research activities Molecular Physiology
Department Prof. Dr. Dorothea Bartels
Dorothea Bartels's research group is concerned with the molecular basis of drought tolerance in plants. To this end, we work primarily with so-called resurrection plant that can adapt to extreme drought, Craterostigma plantagineum. This plant, which belongs to the family of Rachenblütler (Scrophulariaceae) is originally from South Africa and has the remarkable ability to survive extreme drought, as shown in our pictures. The picture right below shows a plant from the drying out, the bottom center picture shows plants after they have received over a period of several days of no water. The plants can survive in this dry stage a long time. The left bottom picture shows plants that were wiederbewässert, after 24 hours.
Craterostigma is therefore particularly suitable as a model system, as well as callus is drought tolerant after treatment with the plant hormone abscisic acid (ABA). The ABA treatment induced drought tolerance, while at the molecular level the genes are expressed which are active in the whole plant during the drying process.
Many genes involved in both processes, drying and re-irrigation, are involved, have been isolated from Craterostigma. Some of the genes are homologous to genes that are found in embryos of maturing seeds. This observation indicates that these genes are involved in the training of drought tolerance. The functional analysis of these genes and proteins are important objects of study of the working group. The work of the group is particularly interested in gene regulation and signal transduction during the drying process.
Another area of research, changes in sugar metabolism. In the non-stressed plant enters the unusual sugar 2-Oktulose in large quantities in the leaves. During the drying Oktulose is converted into sucrose, and vice versa in the re-watering. It is believed that the sugar has a protective function.
Craterostigma plantagineum except we use the drought-tolerant grass Oropetium thomaeum in India, and maturing embryos of barley for the study of drought tolerance.
The research projects can be divided into three parts.
1. Studies on the function of drought stress related genes.
During the drying de novo gene products are synthesized to map the different metabolic pathways. Their role and function is investigated in vitro and in vivo experiments (transgenic plants).
2. Identification of regulatory genes and their role in signal transduction.
Therefore different experimental approaches:
- Promoter studies for the identification of cis and trans regulatory factors.
- Phospholipid-mediated signal transduction.
- Identification of proteins that interact with regulatory DNA motifs or regulatory proteins in the yeast one-and two-hybrid system.
- Analysis of transgenic Arabidopsis populations and isolation of mutants in the signal transduction by means of "DNA activation tagging".
- Identification and characterization of potential regulatory genes in callus as a model system:
Craterostigma callus is per se not drought tolerant. By prior treatment with ABA, a drought tolerance and the expression of drought stress-related genes are induced in the callus, however. The treatment of callus tissue with an analog of the natural S-(+)-ABA does lead to the expression of drought stress-associated transcripts, but not to a drought tolerance, ie the callus tissue is no longer vital to dehydration (Chandler et al., 1997. Physiol. Plant. 99, 465-469). This suggests that there may be other ABA-induced factor (s) out there that are essential for the expression of drought tolerance in Craterostigma callus.
3. Studies on molecular and biochemical mechanisms that lead to drastic changes in sugar metabolism:
C. plantagineum is characterized by the fact that 90% consists of the total sugar in the full turgescent Journal of the unusual sugar-C8 (Oktulose). During the drying out of the C8 sugar is converted into sucrose, which accounts for about 40% of the dry weight of a ausgetrockeneten sheet. When re-irrigation is the process reversible.