News on ABA transport, protein degradation, and ABFs/WRKYs in ABA signaling

► ABC-transporters catalyze efflux of ABA from vascular tissues and uptake by target tissues. ► Regulation of ABI3 and ABI5 stability plays a key role in germination/seedling ABA signaling. ► Different ubiquitin E3 ligases negatively and positively regulate ABA signaling. ► The expression of ABFs/AREBs is regulated by WRKY transcription factors. The recent identification of abscisic acid (ABA) transporters provides an important insight into the delivery of ABA from the vascular system and its uptake by target cells. A putative connection with PYR/PYL receptors is envisaged, linking ABA uptake and intracellular perception by a fast and efficient mechanism. Downstream signaling of the core pathway involves regulation of ABA-responsive element binding factors (ABFs/AREBs) through phosphorylation, ubiquitination, and sumoylation in the case of ABI5. Several E3 ligases appear to regulate ABA signaling either positively or negatively, although relatively few targets are known yet. ABFs/AREBs are themselves subjected to transcriptional regulation, and some transcription factors (TFs) harboring the WRKY domain (WRKYs) appear to regulate their expression through W-box sequences present in the promoters of ABFs/AREBs.