Maleen Hartenstein (Friedrich Alexander University Erlangen-Nürnberg)
Confocal microscope image of a cross-section through an haustorium of Cuscuta reflexa, 8 days after the infection of Arabidopsis thaliana. C. reflexa connects to the vascular tissue of its host. Cell walls were stained with pseudo-Schiff propidium iodide. Scale bar: 150 µm. Image: Maleen Hartenstein
Maleen Hartenstein's Master thesis was awarded with the Prize for the Best Plant Science Master Thesis, which was carried out at Friedrich Alexander University Erlangen-Nürnberg in the year 2021
Title: Examination of interspecific plasmodesmata and anatomical characterization of infection sites between Cuscuta reflexa and its host plants
The parasitic plant Cuscuta reflexa manipulates its host and induces the formation of interspecific plasmodesmata to gain unrestricted access to the assimilates of its host plant.
Plasmodesmata are essential for cell-cell communication and the exchange of macromolecules between neighboring cells and tissues in higher plants. The parasitic plant Cuscuta reflexa (engl. dodder) forms symplastic connections to its host plants via plasmodesmata. C. reflexa is a shoot parasite without roots and leaves and completely dependent on nutrients of its hosts. To gain access to host plant assimilates, C. reflexa penetrates the host tissue with haustoria. Searching hyphae grow out of the haustoria and establish a direct connection to the vascular tissue oft the host plant via plasmodesmata. Therefore, C. reflexa is being used as a model to study newly formed interspecific plasmodesmata.
In this work, the anatomy of the contact sites between the searching hyphae of C. reflexa and the host phloem was investigated. For this purpose, pseudo-Schiff propidium iodide (PS-PI)-staining was established as a method for the visualization of interspecific contact sites. PS-PI staining was used to visualize the characteristic hand structure of searching hyphae of C. reflexa that specifically connected to host phloem cells. For further studies of the infection sites, different marker lines were infected with C. reflexa. It was demonstrated that C. reflexa induces the formation of new phloem tissue in the host. Infection of another marker line revealed that C. reflexa induces the formation of new plasmodesmata in the phloem and cortical tissue of the host. Furthermore, it was shown that C. reflexa connects symplastically to the cher1 mutant, although cher1 is impaired in the formation of complex plasmodesmata. Last, it was demonstrated that upon the infection with C. reflexa, the expression of several plasmodesmata-associated genes of A. thaliana is induced.
However, the signal that triggers the formation of plasmodesmata between host and parasite is still unknown and thus subject to future investigation.
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Maleen Hartenstein conducted this work at the Division of Molecular Plant Physiology under the supervision of PD Dr. Ruth Stadler in the group of Prof. Dr. Markus Albert.