Functional Analysis of the Pepper RING-Type E3 Ligase CaANKR1 Involved in Drought Stress Tolerance via Modulation of Abscisic Acid Signaling.

Plants have developed a diverse array of mechanisms that facilitate survival under stress conditions, among which the ubiquitin-proteasome system (UPS) is a post-translational system used to modulate abiotic stress responses at the molecular level. Within the UPS, E3 ligase plays a key role in determining substrate specificity and has been implicated in the abscisic acid (ABA) signaling pathway during drought stress. In this study, we isolated CaANKR1, an ankyrin repeat-containing C3HC4-type RING E3 ligase, from pepper and characterized its functions in plants subjected to drought stress. CaANKR1 expression was induced by various abiotic stresses, including dehydration, salinity, and mannitol. CaANKR1 was found to be localized in the nucleus and to possess E3 ligase activity. Additionally, we generated CaANKR1-silenced peppers and CaANKR1-overexpressing (OE) Arabidopsis transgenic plants to analyze the functional roles of CaANKR1 in response to drought stress. CaANKR1-silenced peppers exhibited enhanced drought tolerance, which was associated with reduced transpirational water loss and increased ABA sensitivity. In contrast, CaANKR1-OE Arabidopsis transgenic plants showed reduced drought tolerance and decreased sensitivity to ABA. Collectively, these findings suggest that CaANKR1 functions as a negative regulator in drought stress responses.