Wheat MAPK cascade mediates SGT1 nuclear entry targeted by a stripe rust effector

Area of Science:

• Plant Molecular Biology
• Plant Pathology
• Biochemistry

Background:

• Mitogen-activated protein kinase (MAPK) cascades are crucial for plant immunity.
• Understanding plant immune signaling is vital for crop protection.

Purpose of the Study:

• To identify and characterize a specific MAPK cascade involved in wheat resistance to Puccinia striiformis f. sp. tritici (Pst).
• To elucidate the mechanism by which Pst effectors interfere with wheat immunity.

Main Methods:

• Yeast-two hybrid assays to identify protein interactions.
• In vitro kinase assays to confirm phosphorylation events.
• Confocal microscopy to track protein localization in plant cells.

Main Results:

• A wheat MAPK cascade (TaMKK2-TaMAPK6-TaSGT1) was identified, enhancing nuclear entry of TaSGT1 and conferring resistance to Pst.
• The Pst effector HASP215 targets TaMKK2, disrupting the TaMKK2-TaMAPK6 interaction and inhibiting TaMAPK6 activation.
• This disruption leads to reduced TaSGT1 phosphorylation, decreased nuclear translocation, and suppressed plant immunity.

Conclusions:

• The TaMKK2-TaMAPK6-TaSGT1 cascade positively regulates wheat immunity against stripe rust by modulating TaSGT1.
• The Pst effector HASP215 suppresses wheat immunity by targeting this MAPK cascade, revealing a novel pathogenicity mechanism.