Student projects
Unravelling plant defence signals
Plants are organisms that cannot move so they have evolved several mechanisms to face environmental stress. When a leaf is wounded or is infected by pathogenic bacteria many signals are triggered into the whole plant and the combination of these informations are fundamental for life and death struggle. In our lab we are interested in shedding light in this complex field, plant signal transduction, to reach a basal knowledge on which applied research is established ( develop resistance to stress ). In particular we pointed our attention on E-2-hexenal, a volatile compound, emitted under mechanical or biotic stress, that we have found is related with GABA, another molecule that is induced during several kinds of stress. Our aim is to discover the connection between these two signals and also with the others plant signals that trigger defences, such as jasmonic acid and salicylic acid.
Pseudomonas syringae and Arabidopsis thaliana are the two components of our biological system. We have several lines of Arabidopsis, for example one which overproduce GABA, another one that has a lower synthesis of E-2-hexenal, and different strains of Pseudomonas that we would like to use to trigger a response in these plants. To analyse the plant-pathogen system we use a wide range of experimental approaches like molecular biology techniques (DNA/RNA isolation, cDNA synthesis, PCR, quantitative PCR, plant transformation), biochemistry techniques (quantification of plant hormones an signalling molecules with LC/MS and GC/MS), biological assays (Pseudomonas infection of plants and score symptoms on leaves) and microbiology techniques (collect leaves infiltrated with bacteria and check their growth after it).Controlling insect pest by improving the plants defence
On commercial tomato three arthropod pests constitute enormous problems for agriculture; aphids, whiteflies and spider mites. In our lab we have been working on tomato-whitefly and tomato-spider mite interactions for many years. The long-term aim of this research is to develop resistance to infestation.
Whitefly (Bemisia tabaci ) is the vector of viruses in tomato and control of virus infection will be based on prevention of infection. It appears that the host plant is an important factor in selection for resistance; some tomato cultivars appear to exhibit resistance to whitefly infestation and repel whitefly through the production of specific compounds (terpenoids). Previously we established which compounds can decrease whitefly visitation. Forthis internship we will try to elucidate part of the pathway of terpenoid production and its regulation at the level of terpene biosynthesis which finally will result in application in breeding programmes. We have cloned several key enzymes in the terpenoid biosynthesis pathway and have created transgenic tomato lines. These lines will be characterised at gene-expression level (Q-PCR) and production of volatile terpenes (Gas Chromatography-Mass Spectrometry). The effect of altered terpene biosynthesis on whitefly (or spider mite) visitation can then be assessed in bioassays. New terpene synthases will be cloned in expression vectors for in-vivo production of terpenes (by expression in E. coli ), in order to find out which products they actually make. This can also be done by transient expression in a tobacco plant via Agrobacterium infiltration. We check whether the gene is expressed and if so, which volatiles are produced. Experimental techniques include molecular, biochemical and ecological assays (cloning, E. coli expression, GG-MS, DNA/RNA isolation, cDNA synthesis, PCR and quantitative PCR, bioassays)