Biology subjects

Hittorf, M.

Publications and source records attributed to Hittorf, M..

3 recordsLinked to original sources

bioRxiv2025

Under the cover of darkness: how clubroot disease affects Arabidopsis thaliana physiology during the night

Plasmodiophora brassicae (Phytomyxea, Rhizaria) is the etiological agent of clubroot disease, one of the most important diseases of Brassicaceae crops. Alteration of metabolism and hormone homeostasis leads to the formation of tumour-like galls in the roots of affected plants. Host plant energy metabolism, defence and developmental processes are under strong temporal control and the very same processes are affected by clubroot. For the first time, this study uses time-resolved transcriptome analyses to explore how P. brassicae affects Arabidopsis thaliana in the night during intermediate (14 days after inoculation; DAI) and late (21 DAI) infection. Day-night differences in gene expression were more pronounced in younger rather than older plants in our differential gene expression (DGE) analysis. Consequently, intermediate phases of infection showed more day-night differences than later ones. Clustering of differentially expressed genes (DEGs) in functional categories highlighted how some of the typical processes known to be disrupted by clubroot infection are more significantly affected in the night and also uncovered some disrupted exclusively in the night. RNA modification stood out as the most unambiguously upregulated process in infected Arabidopsis roots in the night. Analysis of the interaction between clubroot infection and diel oscillations in gene expression detected modifications in the rhythmicity of central circadian clock components during the infection. We discuss our findings in the context of manipulation of plant defence and metabolism, identifying targets for experimental validation and highlighting potential new lines of investigation of our time-resolved datasets to better understand the interaction between P. brassicae and its host. Significance statementPlasmodiophora brassicae impacts physiological processes under strong temporal control in Brassicaceae hosts: e.g., metabolism, hormone homeostasis and defence. Here, for the first time, we performed a time-resolved transcriptomic exploration of clubroot disease at intermediate and mature stages of infection. We identify a previously unrecognised role for nocturnal manipulation of organellar RNA editing and disruption of rhythmicity in circadian clock components. We provide a dataset enabling further exploration of the impact of clubroot on plant circadian processes.

plant biology↗

bioRxiv2023

Local endoreduplication of the host is a conserved process during Phytomyxea-host interaction

Endoreduplication is a modified cell cycle in which cells duplicate their DNA without subsequent mitosis. This process is common in plants and can also be found in other organisms like algae and animals. Biotrophic plant pathogens have been shown to induce endoreduplication in their host to gain space and/or nutrients. Phytomyxea (divided into the Plasmodiophorida, the Phagomyxida, and the Marinomyxa clade) are obligate biotrophic parasites of plants, diatoms, brown algae, and oomycetes. Here, we tested if phytomyxids induce local endoreduplication in two distant hosts (plants and brown algae). By combining fluorescent in situ hybridisation (FISH) coupled with nuclear area measurements and flow cytometry, we confirmed that endoreduplication is induced by Plasmodiophora brassicae (Plasmodiophorida) in infected plants and demonstrate this process in combination with Maullinia ectocarpii and Maullinia braseltonii (Phagomyxida) in brown algae. We identified molecular signatures of endoreduplication in RNA-seq datasets of P. brassicae-infected Brassica oleraceae and M. ectocarpii-infected Ectocarpus siliculosus. Cell cycle switch proteins (CCS52A1 and B in plants and CCS52 in algae) as well as the protein kinase WEE1 (in plants) were identified as genes potentially important for the phytomyxean-induced switch from the mitotic cell cycle to the endocycle. Their expression pattern changed in infected plants and brown algae accordingly. In this study we expand the knowledge on Phytomyxea-host interactions by showing that induced endoreduplication in the host is a conserved feature in phytomyxid infections. The induction of this cellular mechanism by phytomyxid parasites in phylogenetically distant hosts further points at a fundamental importance of endoreduplication in these biotrophic interactions.

microbiology↗

bioRxiv2022

Phagocytosis underpins the biotrophic lifestyle of intracellular parasites in the class Phytomyxea (Rhizaria)

Phagocytosis is a complex multi-gene trait of eukaryotes and allegedly one of the very defining features of this group. Although well documented for free-living unicellular eukaryotes and in specific cellular types of animals, data on phagocytosis in intracellular biotrophic parasites are scant. Indeed, the definition of intracellular biotrophy as complete reliance of a parasite on a living host, with which it constantly negotiates for the exchange of nutrients, is at odd with the consumption of particulate matter suggested by phagocytosis. Phytomyxea are intracellular biotrophic parasites infecting a broad group of hosts, ranging from plants to stramenopiles. They belong to the clade Rhizaria, where phagotrophy (i.e., phagocytosis as main mode to acquire nutrients) is the main mode of nutrition. The exact mode of nutrition of the biotrophic phytomyxea, including the agriculturally impactful phytomyxid Plasmodiophora brassicae, is still unresolved; despite investigations and the availability of molecular data. For other Phytomyxea, observations are patchy and molecular data altogether lacking. Here, using available genomic and transcriptomic data for Phytomyxea and the de novo sequenced transcriptome of the brown algae parasite Maullinia ectocarpii, we investigate the likelihood that the genetic machinery underpinning phagotrophy is conserved within the clade. We further document intracellular phagocytosis in P. brassicae and M. ectocarpii by transmission electron microscopy and fluorescent in situ hybridization. Our investigations confirm that molecular signatures underpinning phagocytosis exist in Phytomyxea and hint at a smaller subset of genes used for intracellular phagocytosis, which is similar between the two parasites. Microscopic evidence confirms the existence of intracellular phagocytosis, which seems to coexist with the manipulation of host physiology typical of biotrophic interactions. In both phytomyxid parasites investigated intracellular phagocytosis has adapted to the intracellular environment and seemingly targets specific organelles. Our findings shed light on the feeding behaviour of Phytomyxea, providing new molecular data for the class; and suggest a paramount and previously unrecognised role for phagocytosis in biotrophic interactions between host and parasite.

microbiology↗