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A 1-phytase type III effector interferes with plant hormone signaling
Doreen Blüher1, Debabrata Laha2,3, Sabine Thieme1
1Institute for Biology, Department of Genetics, Martin-Luther University Halle-Wittenberg, Weinbergweg 10, 06120, Halle (Saale), Germany.
Xanthomonas bacteria use a type III effector (T3E) called XopH, which has phytase activity, to break down phytate (InsP6) in plants. This breakdown is crucial for pathogen virulence and plant defense responses.
Area of Science:
- Plant Pathology
- Molecular Biology
- Biochemistry
Background:
- Gram-negative bacteria use type III effectors (T3Es) to manipulate plant signaling.
- Plant immune receptors recognize T3Es to halt pathogen invasion.
- The function and recognition of most T3Es are not well understood.
Purpose of the Study:
- To elucidate the molecular function of the Xanthomonas T3E XopH.
- To understand the recognition mechanism of XopH in resistant plants.
- To investigate the role of XopH's enzymatic activity in plant-pathogen interactions.
Main Methods:
- Biochemical assays to determine phytase activity.
- NMR-based methods to identify inositol polyphosphate enantiomers.
- Plant infection assays in Nicotiana benthamiana and pepper.
Main Results:
- XopH exhibits phytase activity, specifically dephosphorylating phytate (myo-inositol-hexakisphosphate, InsP6) at the C1 position.
- XopH converts InsP6 to InsP5 during Xanthomonas infections in plants.
- The 1-phytase activity of XopH is essential for plant immunity mediated by the Bs7 resistance gene.
Conclusions:
- XopH functions as a 1-phytase, targeting the plant's phosphate storage compound InsP6.
- XopH's phytase activity is a key virulence factor for Xanthomonas.
- XopH activity contributes to the induction of plant defense signaling pathways, including jasmonate and ethylene responses.
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