6.125

CHARACTERISATION OF WOUND RESPONSE IN BRASSICA NAPUS AND ARABIDOPSIS THALIANA


CHARACTERISATION OF WOUND RESPONSE IN BRASSICA NAPUS AND ARABIDOPSIS THALIANA

JON ISAKSSON, ERIK ANDFTASSON, BO PONTOPPIDAN, LARS R-ASKl, and JOHAN MEIJER
Dept. of Plant Biology, Uppsala Genetic Center, SLU, S-750 07 Uppsala, Sweden
1 Dept. of Medical and Physiological Chemistry, Biomedical Center,Uppsala University, S-751 23 Uppsala, Sweden.

Background and Objectives

The defence of plants against herbivore attack involves both preformed and inducible components. The myrosinase-glucosinolate system present in cruciferous plants is an example of one such preformed defence where the enzyme myrosinase acts on glucosinolates to produce a variety of products with different toxicity [ 1 ]. A number of wound inducible defence proteins have also been discovered e.g. proteinase inhibitors. We are studying the structure, function and regulation of myrosinases and connected proteins in Brassicaceae. In oilseed rape Brassica napus, myrosinases constitute a gene family with approximately twenty members while myrosinase binding proteins (MBP) and myrosinase associated proteins (MYAP) constitute smaller gene families. We have recently discovered wound inducible forms of MBP and MYAP in oilseed rape. We now want to dissect the signal transduction pathway leading to transcriptional activation of these genes. For this purpose we have also started to explore the oilseed rape relative Arabidopsis thaliana as a model system for wounding.

Results and Conclusion

Analysis of the kinetics of wound response in primary leaves of oilseed rape showed maximal transcript levels of MYAP and MBP at 6 h after wounding or methyl jasmonate treatment. The MRNA levels were back at normal in 24 h after challenge. Similar studies are now being performed in Arabidopsis after chemical or mechanical stimulation. We are using different Arabidopsis mutants to dissect the signal transduction pathway involved in the wound response. We are at present studying jasmonate insensitive mutants with defect jasmonate biosynthesis to elucidate the effects on wound response after challenge. We are employing cell suspension cultures derived from Arabidopsis for biochemical studies of different steps involved in the signal transduction pathway. Although the myrosinase genes in Arabidopsis are fewer compared to oilseed rape the number of genes encoding for MBPs are more abundant in Arabidopsis. We are now generating antisense oilseed rape and Arabidopsis plants with respect to several of the proteins present in the myrosinase system. The antisense plants will be challenged with insects and pathogens to study the effects of the changed myrosinase system on the defence properties of the plants. This study was supported by the Foundation for Strategic Research and the Swedish Research Council for Forestry and Agricultural.

References

[1] Bones A.M. and Rossiter J.T. (1996) Physiol. Plantarum 97, 194-208