An effector from the Huanglongbing-associated pathogen targets citrus proteases

Area of Science:

• Plant Pathology
• Molecular Biology
• Agricultural Science

Background:

• Huanglongbing (HLB) is a devastating citrus disease caused by 'Candidatus Liberibacter asiaticus' (CLas).
• There is currently no known resistance to HLB in citrus cultivars.
• Understanding HLB pathogenesis is critical for developing effective disease management strategies.

Purpose of the Study:

• To investigate the role of Sec-delivered effector 1 (SDE1) in CLas virulence.
• To elucidate the molecular mechanisms by which CLas affects citrus plants.
• To identify potential targets for HLB control.

Main Methods:

• Utilized SDE1 as a molecular probe to study CLas virulence.
• Investigated the interaction between SDE1 and citrus papain-like cysteine proteases (PLCPs).
• Analyzed PLCP activity in CLas-infected citrus and SDE1-expressing transgenic citrus.

Main Results:

• SDE1 directly interacts with and inhibits the activity of citrus PLCPs.
• PLCPs are defense-inducible and increase in abundance during CLas infection.
• SDE1 expression in citrus leads to reduced PLCP activity, indicating SDE1's role in suppressing plant defenses.

Conclusions:

• SDE1 is a key virulence factor of CLas that inhibits citrus immune-related proteases (PLCPs).
• Inhibition of PLCPs by SDE1 likely contributes to HLB pathogenesis by suppressing plant defense responses.
• Targeting the SDE1-PLCP interaction could be a novel strategy for HLB management.