Abstract
Drought stress from soil or air limits plant growth and development, leading to a reduction in crop productivity. Several E3 ligases positively or negatively regulate the drought stress response. In the present study, we show that the pepper (Capsicum annuum) Drought Induced RING type E3 ligase 1, CaDIR1, regulates the drought stress response via abscisic acid (ABA)-mediated signaling. CaDIR1 contains a C3HC4-type RING finger domain in the N-terminal region; this domain functions during protein degradation via attachment of ubiquitins to the substrate target proteins. The expression levels of the CaDIR1 gene were suppressed and induced by ABA and drought treatments, respectively. We conducted loss-of-function and gain-of function genetic studies to examine the in vivo function of CaDIR1 in response to ABA and drought stress. CaDIR1-silenced pepper plants displayed a drought-tolerant phenotype characterized by a low level of transpirational water loss via increased stomatal closure and elevated leaf temperatures. CaDIR1-overexpressing (OX) Arabidopsis plants exhibited an ABA-hypersensitive phenotype during the germination stage, but an ABA-hyposensitive phenotype—characterized by decreased stomatal closure and reduced leaf temperatures—at the adult stage. Moreover, adult CaDIR1-OX plants exhibited a drought-sensitive phenotype characterized by high levels of transpirational water loss. Our results indicate that CaDIR1 functions as a negative regulator of the drought stress response via ABA-mediated signaling. Our findings provide a valuable insight into the plant defense mechanism that operates during drought stress.
Highlights
Plants are sessile organisms; they encounter various environmental stress conditions— including biotic and abiotic stresses
The C3HC4 type Really Interesting New Gene (RING) finger motif, which is essential for E3 ligase in the ubiquitin–26S proteasome system, is located in the N-terminal region of CaDIR1
Our results indicate that the reduced capacity for water retention of CaDIR1-OX plants is derived from abscisic acid (ABA) hyposensitivity, and this contributes to a drought-sensitive phenotype
Summary
Plants are sessile organisms; they encounter various environmental stress conditions— including biotic and abiotic stresses. These stresses lead to inhibition of plant growth and development. Plant perceive a signal through sensors; this process triggers the expression of defense-related genes and the biosynthesis of the plant hormone abscisic acid (ABA) ABA plays a crucial role in adaptation to biotic and abiotic stresses—including drought stress—via regulation of various defense-related genes involved in plant survival through modifications of root hydraulic conductivity, osmotic adjustment, and changes in stomatal aperture (Sirichandra et al, 2009; Lim et al, 2015a). The plant defense response via ABA signaling is a complex phenomenon; the precise functional modifications induced by abiotic stress remain unclear
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