Stress signalling during nematode-plant interaction

Plant-nematode parasitism on cultivated crop species became a big issue in modern agriculture, since billions of EUR are lost world wide due to nematode activity. The main obstacle in fighting against these parasites is the long- term endurance of the cysts in the soil and their resistance to highly toxic chemicals. Thus, the number of available techniques against nematode parasitism is limited and development of new strategies is urgently required. Presently, much hope is laid into molecular biological approaches in order to elucidate essential mechanisms for nematode parasitism. This information is needed for plant breeders in order to produce more tolerant or resistant plant cultivars. Infection of the beet cyst nematode Heterodera schachtii and host plant responses can be successfully studied with model plant Arabidopsis thaliana. Here, we propose to investigate Arabidopsis plant lines with modified stress signalling components protein phosphatases and kinases, of their responses to parasitic nematodes. Such plants with modified signalling components were shown to demonstrate enhanced resistance to herbivorous insects due to modulation in plant stress hormone production and stress signalling cascades. We assume that screening these modified plants for nematode-related phenotypes will generate more understanding in plant-nematode interaction and produce valuable information to be applied directly to crops for breeding towards enhanced nematode control.

Plant-nematode parasitism on cultivated crop species became a big issue in modern agriculture, since these pests cause billions of EUR losses world-wide. The main obstacle in fighting against cyst nematodes is the long-term endurance of the cysts in the soil and their resistance to highly toxic chemicals. Thus, the number of available pest management approaches is limited and development of new strategies is urgently required. Presently, much hope is laid into molecular biological approaches in order to elucidate mechanisms underlying the susceptible host-nematode interaction. Plant breeders use such knowledge in order to produce more tolerant or resistant plant cultivars. A successful cyst nematode infection starts with the detection and correct recognition of the host plant by the migrating nematode juveniles in the soil. The juveniles move towards plant roots, penetrate them and migrate between the plant cells towards the root centre where they induce the formation of specific feeding cell structures. All these infection steps are supposed trigger plant stress responses, however these processes are poorly studied to date. Thus, the main objective of the project was to study plant signalling cascades that induce stress response during the onset of nematode infection. For the current study the interaction between the plant Arabidopsis thaliana and the cyst nematode Heterodera schachtii was selected, that proved as valuable research model in recent decades. First, the role of protein phosphatases and kinases as essential stress signalling components for nematode infection and development was investigated in genetically modified Arabidopsis lines. Previous studies showed that a lack of specific phosphatases intensifies plant defence responses. The results of the current work showed that this lack induces plant attraction and nematode infection however nematode development was reduced. Thus, these plants attract the parasites, but offer harsh conditions for their development. In depth analyses revealed that phosphatases are activated primarily during nematode migration and early infection. Next, the role of down-streams signalling compounds was studied in order to elucidate which signalling pathways get further activated by nematode attack. Plant hormones such as jasmonic acid, ethylene or salicylic acid are main compounds in pathogen-induced plant communication. Hormone application, hormone level determination and analyses of marker gene expression showed that some hormones act attractive and beneficial for nematode infection and development while others do have repellent properties. Finally, a plant symbiont was applied in order to test its effects on the plants hormone metabolisms and thus its effect on nematode infection.