Tracing Xanthomonas translucens evolution reveals gene loss for broad host range emergence

ABSTRACT: Epidemic preparedness depends on tracking microbial evolution that drives disease emergence. For outbreaks caused by host jump, we often identify the causal agent, but functional validation of pathogen emergence lags behind. Here, we defined the role of effector gene loss in the emergence of a generalist lineage of Xanthomonas translucens, an important bacterial plant pathogen of cereals and grasses. This lineage, X. translucens pv. undulosa, causes disease in multiple genera of cereals and grasses and encodes significantly fewer virulence effector genes than the specialist sister lineage X. translucens pv. translucens, which infects barley only. Genomic analyses suggested events contributing to host expansion, and we experimentally reproduced effector gene loss evolution by deleting the effectors unique to the specialist lineage. Notably, deletion of the previously uncharacterized effector gene xopAL1 promoted host expansion to wheat but reduced fitness in barley, supporting a fitness tradeoff for niche expansion. Furthermore, transcriptomic analysis revealed specific XopAL1-dependent defense response components of wheat. Three candidate defense response genes were identified and validated for their functional role in defense against X. translucens via individual targeted gene induction using artificial transcription activator-like effectors (arTALEs). Conversely, we identified that the barley specialist lineage Xtt gained the effector gene xopAJ, which limits disease development in oat but may contribute to barley adaptation. This research provides an experimentally validated evolutionary framework for predicting pathogen emergence based on gene loss, and host adaptation via gene gain, and identifies key host defense components for durable disease control.

ORGANISM(S): Triticum aestivum

PROVIDER: GSE299780 | GEO | 2026/06/12

REPOSITORIES: GEO