Two structurally different oomycete lipophilic microbe-associated molecular patterns induce distinctive plant immune...

Area of Science:

• Plant Pathology
• Molecular Plant-Microbe Interactions
• Biochemistry

Background:

• Plants possess sophisticated defense mechanisms against pathogens, relying on the recognition of non-self molecules.
• Microbe-associated molecular patterns (MAMPs) are key elicitors of plant immunity, but oomycete MAMPs are less understood than bacterial or fungal ones.
• Phytophthora infestans, the late blight pathogen, poses a significant threat to potato crops.

Purpose of the Study:

• To identify novel MAMPs from the oomycete Phytophthora infestans.
• To characterize the plant defense responses induced by these identified MAMPs in potato (Solanum tuberosum).
• To elucidate the specific molecular structures responsible for defense induction and explore cross-talk between MAMP signaling pathways.

Main Methods:

• Utilized reactive oxygen species (ROS) and phytoalexin production in potato as bioassays to detect elicitor activity.
• Isolated and characterized ceramides and diacylglycerols from P. infestans.
• Determined the essential molecular patterns within these elicitors using chemical analysis and tested their effects on Arabidopsis thaliana gene expression.

Main Results:

• Identified two distinct classes of P. infestans elicitors: ceramides (Pi-Cers) inducing ROS production and diacylglycerols (Pi-DAGs) containing eicosapentaenoic acid (EPA) that induce phytoalexins.
• Pinpointed 9-methyl-4,8-sphingadienine (9Me-Spd) in ceramides and 5,8,11,14-tetraene-type fatty acid (5,8,11,14-TEFA) in diacylglycerols as the key microbe-associated molecular patterns.
• Demonstrated that Arabidopsis treated with Pi-Cer D and EPA showed partially overlapping yet distinct gene expression patterns, with some genes uniquely upregulated by combined treatment.

Conclusions:

• Discovered novel oomycete MAMPs, 9Me-Spd and EPA-containing TEFA, recognized by plants and essential for triggering defense.
• These findings expand the known repertoire of MAMPs and highlight their structural diversity in oomycetes.
• Plants integrate signals from simultaneously perceived MAMPs to fine-tune their defense strategies against pathogens like P. infestans.