E3 ubiquitin ligases and abscisic acid signaling

Abstract

The ubiquitin proteasome system is involved in the regulation of nearly every aspect of plant growth and development. Protein ubiquitination involves the covalent attachment of ubiquitin to target proteins through a cascade catalyzed by three enzymes known as E1, E2 and E3. E3s, which are of particular interest as they confer substrate specificity during ubiquitination through their diverse substrate recognition domains. Recently, a number of E3s have been identified that actively participate in abscisic acid hormone biology, including regulation of biosynthesis, de-repression or activation of abscisic acid response and degradation of signaling components. In this review, we summarize recent exciting studies of the different type of E3s that target specific mediators of abscisic acid signaling or affect the plants response to the hormone.

Figure 1

Summary of E3 ligases in the ABA Signaling. U-box type E3s: SAUL1 inhibits ABA biosynthesis; PUB9 is a negative regulator of ABA signaling and function at/or upstream of the ABI3 transcription factor. RING-type E3s: SDIR1 is a positive regulator of ABA signaling that acts upstream of ABI5-like bZIP transcription factors; AIP2 promotes ABI3 degradation; KEG is a negative regulator that modulates ABI5 protein abundance. CRLs: DWA1 and DWA2 are also required for maintaining appropriate levels of ABI5.