Selective Autophagy Receptor CsNBR1 Confers Citrus Huanglongbing Resistance by Degrading ‘ Candidatus Liberibacter Asiaticus’ Virulence Effectors

ABSTRACT

The selective autophagy receptor NEIGHBOUR OF BRCA1 (NBR1) is a key regulator of plant immunity, but its role against bacterial pathogens remains poorly understood. Here, we demonstrated that overexpression of CsNBR1 confers citrus resistance to huanglongbing (HLB) caused by ‘ Candidatus Liberibacter asiaticus’ ( C Las). CsNBR1 can interact with multiple virulence effector proteins of C Las, including SDE5115, SDE1, SDE19 and SDE5, leading to their degradation via the autophagic pathway. In addition, expression of CsNBR1 in Nicotiana benthamiana mitigated the leaf curling and dwarfing phenotypes triggered by SDE1 by reducing the protein content of SDE1. These findings reveal that CsNBR1 positively regulates citrus defence against C Las by degrading its effector proteins via selective autophagy, providing both mechanistic insights and a potential target for resistance breeding.