The Exocyst Subunits EqSec5 and EqSec6 Promote Powdery Mildew Fungus Growth and Pathogenicity

Area of Science:

• Molecular and Cellular Biology
• Plant Pathology
• Mycology

Background:

• The exocyst complex regulates vesicle transport and exocytosis in eukaryotic cells.
• It plays a role in hyphal growth and pathogenicity in filamentous fungi.
• The exocyst's function in obligate biotrophic powdery mildew fungi remains largely uncharacterized.

Purpose of the Study:

• To investigate the role of the exocyst complex in the powdery mildew fungus *Erysiphe quercicola*.
• To identify and characterize exocyst subunits involved in fungal growth and pathogenicity.

Main Methods:

• Identification and localization of exocyst subunits (EqSec5, EqSec6) using GFP fusion proteins.
• Gene silencing of *EqSec5* and *EqSec6* to assess phenotypic effects.
• Yeast two-hybrid and gene overexpression assays to study protein interactions.

Main Results:

• EqSec5 and EqSec6 localized to the hyphal tip region in *E. quercicola* and *Magnaporthe oryzae*.
• Gene silencing of *EqSec5* or *EqSec6* resulted in significant growth and infection defects.
• Silencing inhibited effector protein secretion, disrupted salicylic acid biosynthesis, and triggered host defense responses.

Conclusions:

• The exocyst complex is essential for effector secretion, hyphal growth, and host infection in *E. quercicola*.
• EqSec5 and EqSec6 interact and complement each other's function during pathogenesis.
• This study elucidates the exocyst's critical role in powdery mildew fungal development and pathogenicity.