Biology subjects

Steentjes, M.

Publications and source records attributed to Steentjes, M..

3 recordsLinked to original sources

bioRxiv2026

Development of a CRISPR/Cas9-mediated transformation procedure for the wheat pathogen Zymoseptoria tritici

Zymoseptoria tritici is the causal agent of Septoria tritici blotch (STB), one of the most destructive diseases of wheat worldwide. Although the Z. tritici genome encodes hundreds of predicted effector proteins, functional characterization through the use of genome-editing techniques has been limited due to low homologous recombination efficiency and extensive effector redundancy. In this study, we established and evaluated a CRISPR/Cas9-based genome editing procedure for targeted effector gene disruption in Z. tritici using in vitro-assembled Cas9-sgRNA ribonucleoprotein (RNP) complexes combined with short (60 bp) homologous donor DNA flanks. Using this approach, we successfully generated knockout mutants for a selected candidate effector gene, the Hce2 domain-containing effector Mycgr3107904. Virulence assays on the susceptible wheat cultivar Taichung 29 revealed that two independent{Delta} Mycgr3107904 mutants exhibited a pronounced delay in symptom development compared to the wild-type strain IPO323, with disease onset and progression delayed by approximately 4-5 days. While mutant strains ultimately followed a similar disease trajectory, wild-type-infected leaves displayed extensive necrosis and pycnidia formation at earlier time points, indicating a significant reduction in virulence upon loss of Mycgr3107904. Together, our results demonstrate the feasibility of CRISPR/Cas9-mediated effector gene knockout in Z. tritici and provide functional evidence that Mycgr3107904 contributes to timely disease progression. This work advances genome editing tools for Z. tritici and facilitates systematic dissection of effector functions underlying fungal virulence.

genetics↗

bioRxiv2023

A chromosome-level genome assembly of Zasmidium syzygii isolated from banana leaves

Accurate taxonomic classification of samples from infected host material is essential for disease diagnostics and genome analyses. Despite the importance, diagnosis of fungal pathogens causing banana leaf diseases remains challenging. Foliar diseases of bananas are mainly caused by three Pseudocercospora species, of which the most predominant causal agent is P. fijiensis. Here, we sequenced and assembled four fungal isolates obtained from necrotic banana leaves in Bohol (Philippines) and obtained a high-quality genome assembly for one of these isolates. The samples were initially identified as P. fijiensis using PCR diagnostics, however, the assembly size was consistently 30 Mb smaller than expected. Based on the ITS sequences, we identified the samples as Zasmidium syzygii (98.7% identity). The high-quality Zasmidium syzygii assembly is 42.5 Mb in size, comprising 16 contigs, of which 11 are complete. The genome contains 98.6% of the expected single-copy BUSCO genes and contains 14,789 genes and 10.3% repeats. The three short-read assemblies are less continuous but have similar genome sizes (40.4 - 42.4 Mb) and contain between 96.5% and 98.4% BUSCO genes. All four isolates have identical ITS sequences and are distinct from Zasmidium isolates that were previously sampled from banana leaves. We thus report the first continuous genome assembly of a member of the Zasmidium genus, forming an essential resource for further analysis to enhance our understanding of the diversity of pathogenic fungal isolates as well as fungal diversity.

microbiology↗

bioRxiv2018

Exocyst subunit Sec6 is positioned by microtubule overlaps in the moss phragmoplast prior to the arrival of cell plate membrane

During plant cytokinesis a radially expanding membrane-enclosed cell plate is formed from fusing vesicles that compartmentalizes the cell in two. How fusion is spatially restricted to the site of cell plate formation is unknown. Aggregation of cell-plate membrane starts near regions of microtubule overlap within the bipolar phragmoplast apparatus of the moss Physcomitrella patens. Since vesicle fusion generally requires coordination of vesicle tethering and subsequent fusion activity we analysed the subcellular localization of several subunits of the exocyst, a tethering complex active during plant cytokinesis. We found that Sec6, but neither Sec3 or Sec5 subunits localized to microtubule overlap regions in advance of cell plate construction started in moss. Moreover, Sec6 exhibited a conserved physical interaction with an orthologue of the Sec1/Munc18 protein KEULE, an important regulator for cell-plate membrane vesicle fusion in Arabidopsis. Recruitment of PpKEULE and vesicles to the early cell plate was delayed upon Sec6 gene silencing. Our findings thus suggest that vesicle-vesicle fusion is in part enabled by a pool of exocyst subunits at microtubule overlaps that is recruited independent of the delivery of vesicles.\n\nSummary statementWe performed a time-resolved localization screen of multiple subunits of the exocyst complex throughout moss cytokinesis and show that each subunit has a unique spatiotemporal recruitment pattern.

cell biology↗