Introduction
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During evolution plants have developed a variety of specific defence mechanisms to protect themselves against pathogens and herbivores, as well as abiotic stress. The secondary metabolism of plants, in particular the formation of phenylpropanoids and lignification, is of great importance for this defence strategy of sessile organisms. In addition, this metabolic pathway supports growth and competition with other plants. In our project the secondary pathway is analyzed in connection with competition and host/parasite interactions in herbaceous plants and long lived tree species. Reprogramming of constitutive and inducible parts of phenylpropan, lignin and cellulose formation is studied at the transcriptional and metabolite level. Recently, new regulation switches in the shikimate pathway, which is in front of the phenylpropanoid pathway, were described. Therefore, we also concentrate on genes and enzymes of this pathway (Figure 1) which connects the primary and secondary metabolism.
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Results
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Figure 1: Shikimate and phenylpropanoid pathway in plants
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Upon short-term exposure of ozone DAHPS and EPSPS rapidly respond to this abiotic stress, suggesting the involvement of the aromatic metabolism in plant defence. RT-PCR analysis using leaf material from phytotron experiments (project A7), however, revealed no influence of ozone and elevated CO2 on mRNA levels of the shikimate and phenylpropanoid pathway under long-term exposure.
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Pathogens and endophytes
Figure 2 B: Identification of A. errabunda in leaves of infested and control plants
Apiognomonia errabunda is a major fungal pathogen of European beech with an extended endophytic growth phase. This as well as other fungal pathogens and endophytes of beech leaves were identified by classical plating techniques and by quantitative real time PCR using SCAR sequences for primer design (together with A7, A9). Quantitation of the fungi allows the study of predisposition effects for abiotic stress factors in young trees in chamber experiments as well as in the field.
In addition to the cooperations within the SFB, international cooperations, e.g. the TOMSTRESS project (Engineering tomato against environmental stress) and EU-FAIR (Stilbene metabolism in Scots pine), deal with similar problems of growth and parasite defence (http://www.helmholtz-muenchen.de/biop/.
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Figure 2 A: Beech leaves infected with Apiognomonia errabunda
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