Variation in structure and activity among elicitins from Phytophthora sojae

Area of Science:

• Plant Pathology
• Molecular Biology
• Genetics

Background:

• Elicitins are proteins known to induce plant defense responses.
• Phytophthora sojae is a significant pathogen of soybean, and understanding its secreted proteins is crucial for disease management.

Purpose of the Study:

• To identify and characterize elicitin-like protein domains in Phytophthora sojae.
• To investigate the molecular structure, expression patterns, and elicitor activity of these proteins.

Main Methods:

• Similarity searches of Phytophthora sojae expressed sequence tags (ESTs) to identify elicitin-like genes.
• Bioinformatic analysis of predicted protein structures, including signal sequences, core elicitin domains, and C-terminal regions.
• Analysis of transcript expression patterns in different developmental stages (mycelia, zoospores, infection).
• Testing of selected elicitin domains for hypersensitive response (HR) induction in Nicotiana spp.

Main Results:

• Identified at least nine elicitin genes in P. sojae, including known and novel sequences.
• Characterized structural features, noting conserved domains and unique C-terminal regions, including a membrane-spanning domain in SOJX and SOJY.
• Found differential expression: SOJA-2, SOJB, SOJ2, SOJ3, and SOJ6 expressed in mycelia and during infection, while SOJX and SOJY were specific to zoospores.
• Demonstrated that most tested elicitin domains induced the hypersensitive response (HR), except for SOJX and SOJY.

Conclusions:

• The Phytophthora sojae elicitin gene family is large and structurally diverse.
• Differential expression patterns suggest specialized roles for different elicitins during the pathogen lifecycle.
• Varied HR-inducing activity indicates distinct functions in plant-pathogen interactions.