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Membrane-targeted HrpNEa can modulate apple defense gene expression
Molecular Plant-Microbe Interactions : MPMI
|October 26, 2013
Summary
Fire blight protein HrpNEa (harpin) can trigger plant defenses. When targeted to apple cell membranes, HrpNEa modulated defense genes and slightly reduced infection frequency, suggesting a role in host immunity.
Area of Science:
- Plant Pathology
- Molecular Plant-Microbe Interactions
- Plant Biotechnology
Background:
- Fire blight, caused by Erwinia amylovora, is a significant bacterial disease affecting apple (tribe Maleae).
- The bacterial protein HrpNEa (harpin) is secreted by E. amylovora and can induce hypersensitive response in nonhost plants.
- HrpNEa possesses amyloidogenic properties, forming oligomers that disrupt membrane homeostasis.
Purpose of the Study:
- To investigate the physiological effects of HrpNEa within the host plant (apple).
- To produce transgenic apple plants expressing HrpNEa with or without a secretion signal peptide (SP) for membrane localization.
- To assess the role of membrane-localized HrpNEa in apple defense responses against E. amylovora.
Main Methods:
- Generation of transgenic apple plants expressing HrpNEa with and without a secretion signal peptide (SP).
- Biochemical fractionation to determine HrpNEa localization within plant cells.
- In silico analysis to predict transmembrane domains of HrpNEa.
- Gene expression analysis of 28 apple defense-related genes.
- Inoculation assays with E. amylovora to evaluate disease development and infection frequency.
Main Results:
- HrpNEa expressed with an SP localized to the membrane fraction, consistent with its amyloidogenic nature and predicted transmembrane domains.
- Expression analysis revealed modulation of defense-related genes in transgenic lines with membrane-targeted HrpNEa.
- Apple trees with high constitutive expression of SP-HrpNEa showed a slight reduction in infection frequency but no decrease in disease severity.
Conclusions:
- Membrane localization of HrpNEa in apple plants influences host defense gene expression.
- HrpNEa acts as an elicitor of host defenses when targeted to the host plant cell membrane.
- Targeting bacterial effector proteins to plant membranes offers a potential strategy for modulating plant immunity.
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