The effect of ABRE BINDING FACTOR 4-mediated FYVE1 on salt stress tolerance in Arabidopsis

FYVE1 encodes a protein that is localized to the peripheral membrane of late endosomal compartments, and is involved in the regulation of mulitivesicular/prevacuolar compartment protein sorting. It was found that FYVE1 attenuates ABA signaling through degrading ABA receptors PYR1 and PYL4 by ESCRT pathway, and also interacts with transcription factors ABF4 and ABI5 to transcriptionally inhibit ABA signaling pathway by reducing their binding to the cis-regulatory sequences of their downstream genes. However, the mechanisms underlying the transcriptional regulation of FYVE1 and its biological function in salt stress are largely unknown. Here, we show that fyvel knockdown-mutants show enhanced tolerance to salt stress, while overexpression of FYVE1 results in increased sensitivity to salt stress. Further analysis shows that FYVE1 negatively regulates salt stress tolerance, which is associated with ABA signaling pathway. ABRE BINDING FACTOR 4 (ABF4) directly binds to promoter of FYVE1 to activate its transcription. Moreover, FYVE1 interacts with and promotes degradation of all ABA PYR/PYL receptors. Thus, our results suggest that FYVE1 negatively modulates salt stress tolerance in Arabidopsis via a negative feedback loop.