A ‘Candidatus Liberibacter asiaticus’ effector SDE2470 facilitates citrus transcription factor CsVOZ2 degradation via BRUTUS E3 ligases

Citrus Huanglongbing (HLB), a devastating disease caused by the Gram-negative bacterium 'Candidatus Liberibacter asiaticus' (CLas), poses serious threats to global citrus production and lacks effective control strategies. Previously, SDE2470 (CLIBASIA_02470) was identified as a Sec-dependent effector that contributes to CLas pathogenesis, although its underlying molecular mechanisms were not fully elucidated. In this study, SDE2470 was found to target a citrus vascular one-zinc-finger transcription factor CsVOZ2. CsVOZ2 overexpression (CsVOZ2-OE) in transgenic citrus plants significantly suppressed CLas colonization, whereas its RNA interference (RNAi) in citrus hairy roots enhanced susceptibility to CLas. Additionally, CsVOZ2-OE significantly increased reactive oxygen species (ROS) and abscisic acid (ABA) contents accumulation and activated related genes expression. Further investigation revealed that the E3 ligase CsBTS1 directly interacts with CsVOZ2 and promotes its degradation via the 26S proteasome pathway. CsBTS1E3-OE in citrus hairy roots markedly enhanced CLas proliferation. Importantly, SDE2470 directly interacts with CsBTS1E3 and strengthen CsBTS1E3-CsVOZ2 interaction. Meanwhile, SDE2470 strengthened the E3 ligase activity of CsBTS1, promoting CsVOZ2 degradation. Taken together, these findings support a model in which SDE2470 hijacks CsBTS1 to destabilize CsVOZ2, thereby disrupting ROS- and ABA-dependent immunity and promoting CLas infection in citrus.