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Published on: September 30, 2016
Transcriptomic and Ultrastructural Signatures of K+-Induced Aggregation in Phytophthora parasitica Zoospores
Ilaria Bassani1, Corinne Rancurel1, Sophie Pagnotta2
1Université Côte d'Azur, INRAE, CNRS, ISA, 06903 Sophia Antipolis, France.
Abstract:
Most pathogenic oomycetes of the genus Phytophthora spread in water films as flagellated zoospores. Zoospores perceive and produce signals attracting other zoospores, resulting in autoaggregation in vitro or biofilm formation on plant surface. The mechanisms underlying intercellular communication and consequent attraction, adhesion and aggregation are largely unknown. In Phytophthora parasitica, the perception of a K+ gradient induces coordinated motion and aggregation. To define cellular and molecular events associated with oomycete aggregation, we combined transcriptomic and ultrastructural analyses. Results indicate involvement of electroception in K+ sensing. They establish that the transcriptome repertoire required for swimming and aggregation is already fully functional at zoospore release. At the time points analyzed, aggregates are mainly constituted of zoospores. They produce vesicular and fibrillary material discharged at cell-to-cell contacts. Consistently, the signature of transcriptome dynamics during transition to aggregates is an upregulation of genes potentially related to vesicular trafficking. Moreover, transcriptomic and functional analyses show a strong enhancement of carbonic anhydrase activity, indicating that pH homeostasis may contribute to aggregation by acting on both zoospore movement and adhesion. This study poses the molecular and cellular bases of aggregative behavior within oomycetes and expands the current knowledge of ion perception-mediated dissemination of propagules in the rhizosphere.
Insights
Pathogenic oomycetes like Phytophthora parasitica aggregate through ion sensing. This study reveals molecular mechanisms involving electroception, vesicular trafficking, and pH homeostasis in zoospore aggregation.
Area of Science:
- Plant Pathology
- Microbiology
- Cell Biology
Background:
- Pathogenic oomycetes, particularly *Phytophthora* species, utilize motile zoospores for dissemination.
- Zoospore aggregation and biofilm formation are critical for plant infection but underlying mechanisms remain unclear.
- Intercellular communication, attraction, adhesion, and aggregation processes in oomycetes require detailed investigation.
Purpose of the Study:
- To elucidate the cellular and molecular events governing zoospore aggregation in *Phytophthora parasitica*.
- To define the role of ion perception, specifically potassium (K+) gradients, in coordinating zoospore behavior.
- To identify key molecular pathways and cellular structures involved in oomycete aggregation.
Main Methods:
- Combined transcriptomic analysis with ultrastructural studies to investigate zoospore aggregation.
- Investigated the role of electroception in potassium (K+) sensing and zoospore response.
- Analyzed gene expression profiles and enzyme activity (carbonic anhydrase) during aggregation.
Main Results:
- Potassium (K+) gradient perception triggers coordinated motion and aggregation in *P. parasitica* zoospores.
- The genetic machinery for swimming and aggregation is functional at zoospore release.
- Aggregates primarily consist of zoospores releasing vesicular and fibrillary material, with upregulated genes related to vesicular trafficking.
- Enhanced carbonic anhydrase activity suggests pH homeostasis contributes to zoospore movement and adhesion.
Conclusions:
- This study establishes the molecular and cellular basis for aggregative behavior in oomycetes.
- Ion perception, particularly K+ sensing and pH homeostasis, plays a crucial role in zoospore aggregation and dissemination.
- Findings expand knowledge of how oomycetes spread and infect plants in the rhizosphere.
