Molecular basis of Arabidopsis ABCC2 in plant detoxification

Abstract

Dear Editor , The detoxi fi cation of phytotoxic compounds is a prerequisite for plant survival. ATP-binding cassette family C (ABCC) transporters play a pivotal role in the export of toxic compounds into vacuoles, a critical step in detoxi fi cation 1 . Arabidopsis thaliana ABCC2 ( At ABCC2) is responsible for the ef fl ux of glutathione conjugates of pesticides, such as atrazine and metolachlor, into the vacuoles 2 – 5 . Additionally, At ABCC2 can export arsenic-phytochelatin conjugates into vacuoles, resulting in increased arsenic tolerance 6,7 . Despite its critical role in plant detoxi fi cation, the biochemical and structural mechanisms underlying the function of At ABCC2 remain incompletely understood. To address this gap, we present cryo-electron microscopy (cryo-EM) structures of At ABCC2 in four states: apo, substrate bound, closed, and dimeric. Structural analysis revealed a unique architecture, distinguished by the atypical localization of its transmembrane domain 0 (TMD0) domain. Moreover, biochemical studies revealed that the TMD0 domain is critical for coordinating transport channel closure. The molecular basis of atrazine export by At ABCC2 was also determined. Additionally, the plant-speci fi c dimerization of At ABCC2 was demonstrated to be mediated by TMD2 and nucleotide-binding domain 2 (NBD2) rather than by the TMD0 domain. Notably, we found that although dimeric At ABCC2 represented a physiological form, its dimerization resulted in reduced substrate export activity. These fi ndings provide new insights into the detoxi fi cation mechanism of At ABCC2 and highlight the potential for using ABCC transporters to develop herbicide-resistant crops. Full-length At