Biology subjects

Dubrow, Z. E.

Publications and source records attributed to Dubrow, Z. E..

3 recordsLinked to original sources

bioRxiv2026

Mobile genetic elements accompany the emergence of clonal crop lineages from weed-associated populations of Xanthomonas campestris

Xanthomonas campestris is a destructive pathogen of cruciferous vegetables and ornamentals and is frequently isolated from related weed species growing near agricultural land. However, the evolutionary relationships, genomic features, and biosecurity significance of weed-associated strains remain poorly understood. Here, we integrate phylogenomic and pangenomic analyses of X. campestris, including nine newly sequenced strains isolated from invasive garlic mustard (Alliaria petiolata), to compare strains from cultivated and non-cultivated hosts across multiple pathovars. Weed-isolated strains predominantly clustered within basal, genetically diverse lineages associated with broad host ranges, whereas crop-isolated strains were concentrated in host-associated clonal lineages. The emergence of specialized crop-associated lineages coincided with multiple inferred acquisitions of large mobile elements, including integrative conjugative and mobilizable elements and plasmids carrying genes previously associated with pathogenicity and host range. Although these elements were enriched in clonal crop-associated lineages, they also occurred in diverse weed-associated strains, indicating that genetic material associated with crop infection is distributed among divergent lineages and persists in wild and weedy systems. These findings identify invasive weeds as ancillary hosts that may harbor pathogen diversity and provide opportunities for genetic exchange, underscoring the importance of surveillance beyond agricultural fields to monitor pathogen diversification and emerging threats. Our pangenomic analysis also identified crop-associated pathogen factors and putative host resistance targets for future investigation, providing a foundation for developing critically needed black rot-resistant cultivars.

microbiology↗

bioRxiv2025

A Xanthomonas effector protein contributes quantitatively to virulence by inducing at least two minor Susceptibility genes

The transcription activator-like effector Tal12a is widely conserved among Xanthomonas campestris pv. campestris strains that cause black rot in Brassica crops. However, its role in disease remains unclear. To investigate how Tal12a contributes to pathogenesis, we combined transcriptomic profiling of cauliflower leaves infected with Tal12a-expressing strains, prediction of TALE-binding elements, and heterologous expression assays in Nicotiana benthamiana. The aim of this approach was to identify candidate susceptibility genes. Artificial TALEs were further employed to validate the contribution of these candidate targets to disease development. Tal12a enhanced both virulence and bacterial growth in cauliflower. Transcriptome analysis revealed 380 genes that were induced upon infection, nine of which were prioritised as candidates. Seven of these were confirmed as direct Tal12a targets, while the induction of the sugar transporter genes BoSWEET13 and BoSWEET14c likely occurred indirectly. Functional assays demonstrated that these two SWEET genes and the BoIAA7c gene, which encodes auxin-dependent transcriptional regulator, contribute to disease development. These findings identify the first susceptibility genes in cauliflower and reveal that Tal12a promotes disease through a complex transcriptional reprogramming, involving direct and indirect target induction, with several genes functioning as minor susceptibility factors.

plant biology↗

bioRxiv2020

A TAL effector-like protein of symbiotic Mycetohabitans increases stress tolerance and alters the transcriptome of the fungal host Rhizopus microsporus

Symbioses of bacteria with fungi have only recently been described and are poorly understood. In the symbiosis of Mycetohabitans (formerly Burkholderia) rhizoxinica with the fungus Rhizopus microsporus, bacterial type III (T3) secretion is known to be essential. Proteins resembling T3-secreted transcription activator-like (TAL) effectors of plant pathogenic bacteria are encoded in the three sequenced Mycetohabitans spp. genomes. TAL effectors nuclear localize in plants, where they bind and activate genes important in disease. The Burkholderia TAL-like (Btl) proteins bind DNA but lack the N- and C-terminal regions in which TAL effectors harbor their T3 and nuclear localization signals, and activation domain. We characterized a Btl protein, Btl19-13, and found that, despite the structural differences, it can be T3-secreted and can nuclear localize. A btl19-13 gene knockout did not prevent the bacterium from infecting the fungus, but the fungus became less tolerant to cell membrane stress. Btl19-13 did not alter transcription in a plant-based reporter assay, but 15 R. microsporus genes were differentially expressed in comparisons both of the fungus infected with the wildtype bacterium vs the mutant and with the mutant vs. a complemented strain. Southern blotting revealed btl genes in 14 diverse Mycetohabitans isolates. However, banding patterns and available sequences suggest variation, and the btl19-13 phenotype could not be rescued by a btl gene from a different strain. Our findings support the conclusion that Btl proteins are effectors that act on host DNA and play important but varied or possibly host-genotype-specific roles in the M. rhizoxinica-R. microsporus symbiosis.

microbiology↗