Thrips Resistance In Tomato Plants

Metabolomics has rapidly developed into a valuable technology playing an indispensable role in bridging the gaps in knowledge between phenotypes and genotypes. Together with ecological approaches it links genetics to fitness and function. Despite the general belief that a succesfull applied genomics project requires a combination of molecular, genetic, metabolomic and ecological approaches our programme is one of the first to integrate this range of expertise. We intend to study a phenolic compound, chlorogenic acid (CGA), which acts as an antioxidant in plants and is expected to protect against degenerative, age related diseases. Our programme will study the importance of CGA for plant resistance against herbivorous insects. Specifically we want: - to develop tomato lines resistant to western flower thrips (Frankliniella occidentalis) by increasing natural CGA levels, using a second generation molecular approach. - to explore the natural variation in CGA levels in tomatoes - to increase our understanding of the role of CGA in thrips resistance - to identify the genetics behind CGA production levels - to understand the relationships between CGA and the primary and secondary metabolism - to establish a long-lasting research network for post-genomic research

We will assay the effects of chlorogenic acid (CGA) on thrip resistance in tomato using plants with elevated chlorogenic acid (CGA) levels produced by overexpression techniques that resulted in a doubling of CGA levels. We will develop new lines of tomato with even higher CGA levels by using combinations of transcriptional regulators and the key biosynthetic enzyme HQT. To explore the genetic basis of CGA accumulation we will use a high-throughput gas chromatography/ mass spectrometry protocol to characterize metabolite levels in leaves of tomatoes. Experiments will also address the interaction between primary metabolism and CGA using a mixture of steady-state and dynamic isotope profiling. Secondly, an introgression line population of tomato consisting of 76 lines / in which marker-defined genomic regions of the cultivated variety Solanum lycopersicum were replaced with homologous intervals of the wild species S. pennellii will be screened for CGA content. The ILs represent a unique system for identifying genomic regions associated with changes in metabolism. Given the variation already known, it seems reasonable to expect that this screen will reveal QTL for CGA. Further experiments will include a more detailed analysis to elucidate the genetic basis for enhanced CGA accumulation. Additionally, once these lines have been screened they will be used in physiological studies aimed at studying the interface between CGA content and primary metabolism and secondary metabolism using various spectrometric methods such as UV, NMR and mass spectrometry. We will use bioassays (leaf strip bioassays, choice-tests, non-choice tests) to determine the relation between CGA levels and thrips resistance and its stability; resistance to different thrips biotypes, resistance at different development stages, and under different environmental conditions.