The role of pectin medifications during host invasion and infection by the parasitic plant Phtheirospermum japonicum

Sammanfattning: Parasitic plants are organisms that feed on other plants, often distantly related to them evolutionarily. This feeding strategy causes them to be a major threat to agriculture, negatively affecting the yields of many staple crops like sorghum and rice. To infect their hosts, parasitic plants need to develop an invasive structure known as haustorium, which allows vasculature connection between the two plants and the exchange of nutrients and signalling molecules. A key step for successful parasitism is the invasion of the host tissues by the haustorium. This process relies on the modification of the host’s cell-adhesion, mainly through the action of cell-wall modifying enzymes such as pectin methylesterases (PMEs), peroxidases and pectate lyases. However, despite the importance of this process, the role of these enzymes has not been closely investigated in parasitic plants. In particular, no studies have been performed on the parasitic plant Phtheirospermum japonicum, which is a model for root facultative parasites. The aim of this thesis was to study the role of PMEs in the development of P. japonicum haustoria during parasitism of its host Arabidopsis thaliana. The approach used includes the analysis of newly generated transcriptomics data, as well as pectin-specific staining and the analysis of parasitism efficiency on host cell-adhesion mutants. The results obtained suggest the involvement of PMEs in different stages of haustorium formation, from the early host invasion to later vasculature connection development, setting the basis for more in-depth studies on the subject.