Identification of INOSITOL PHOSPHORYLCERAMIDE SYNTHASE 2 (IPCS2) as a new rate-limiting component in Arabidopsis...

Area of Science:

• Plant pathology
• Molecular biology
• Biochemistry

Background:

• Inositol phosphorylceramide synthase 2 (IPCS2) synthesizes complex sphingolipids at the trans-Golgi network (TGN).
• Sphingolipids play roles in various cellular processes, including membrane trafficking and signaling.

Purpose of the Study:

• To investigate the role of IPCS2 in plant defense against non-adapted powdery mildew fungi.
• To elucidate the mechanism by which IPCS2 contributes to penetration resistance.

Main Methods:

• Forward genetic screen in Arabidopsis to identify mutants with enhanced fungal entry.
• Yeast complementation assay and sphingolipidomic analysis to characterize the mutant.
• Confocal laser scanning microscopy (CLSM) to observe defense protein localization.

Main Results:

• A novel ipcs2 mutant (ipcs2_W205*) showed increased susceptibility to Blumeria graminis f. sp. hordei (Bgh).
• The mutant lacks IPCS2 activity and produces reduced levels of glycosyl inositol phosphorylceramides (GIPCs).
• IPCS2 is required for the focal accumulation of the defense protein PENETRATION 3 (PEN3) at pathogen contact sites.

Conclusions:

• IPCS2-derived GIPCs are essential for controlling the entry of non-adapted fungal pathogens.
• IPCS2 facilitates the TGN-mediated sorting and secretion of PEN3 to sites of fungal invasion.
• Complex sphingolipids regulate polar secretion of defense cargo, terminating fungal ingress.