OsPDCB1 mediates plasmodesmal callose defense and is targeted by a conserved planthopper effector

Area of Science:

• Plant-insect interactions
• Molecular plant pathology
• Plant immunity

Background:

• The brown planthopper (BPH) is a major rice pest, feeding on phloem sap.
• Rice plants defend by depositing callose at plasmodesmata to block feeding.
• The molecular mechanisms of callose stabilization and BPH counter-defense are unclear.

Purpose of the Study:

• To identify rice genes involved in callose-based defense against BPH.
• To elucidate the molecular mechanism of BPH overcoming plant defenses.
• To explore genetic variations for enhancing BPH resistance in rice.

Main Methods:

• Gene identification and characterization (OsPDCB1).
• Loss- and gain-of-function analyses in rice.
• Identification and characterization of a BPH salivary effector (NlVRSP1).
• Analysis of effector-host protein interactions.
• Haplotype analysis and introgression into different rice varieties.

Main Results:

• OsPDCB1, a plasmodesmal callose-binding protein, anchors callose and is crucial for BPH resistance.
• The BPH effector NlVRSP1 interacts with OsPDCB1, disrupting callose binding and phloem immunity.
• A resistance-associated allele, OsPDCB1^Hap1, enhances BPH resistance in susceptible rice backgrounds.

Conclusions:

• OsPDCB1 is a key regulator of callose-based defense against BPH.
• NlVRSP1 represents a novel insect effector strategy targeting plasmodesmal immunity.
• OsPDCB1 offers a promising genetic target for developing BPH-resistant rice cultivars.