Roles of pepper bZIP protein CaDILZ1 and its interacting partner RING‐type E3 ligase CaDSR1 in modulation of drought tolerance

Abstract

Abscisic acid (ABA) is a plant hormone that plays a key role in the environmental stress response, especially the induction of ABA-responsive and stress-responsive genes and modulation of the stomatal aperture in response to drought stress. Here, we identified CaDILZ1 (Capsicum annuum Drought-Induced Leucine Zipper 1) belonging to subgroup D of the bZIP protein family; gene functions of this family in response to ABA and drought signaling still remain unknown. CaDILZ1 expression was significantly induced in pepper leaves after exposure to ABA, drought, and NaCl. The CaDILZ1 protein localized in the nucleus of plant cells. In response to drought stress, CaDILZ1-silenced pepper and CaDILZ1-overexpressing Arabidopsis plants exhibited drought-sensitive and drought-tolerant phenotypes, respectively, via altered ABA content, stomatal closure, and expression of ABA-responsive and drought-responsive marker genes. We isolated the RING finger protein CaDSR1 (Capsicum annuum Drought Sensitive RING finger protein 1), which interacted with CaDILZ1 in the nucleus. The CaDSR1 protein exhibited E3 ligase activity and promoted CaDILZ1 degradation via the 26S proteasome pathway. Under drought stress conditions, CaDSR1-silenced pepper and CaDSR1-overexpressing Arabidopsis plants exhibited contrasting phenotypes to those of CaDILZ1-silenced pepper and CaDILZ1-overexpressing Arabidopsis plants. Taken together, our data suggest that CaDSR1 and CaDILZ1 function in ABA-mediated drought stress signaling in pepper plants.

Research Progress on Plant RING-Finger Proteins

“…These RING-fingers are mainly used as ubiquitin ligase E3 to degrade other proteins through the 26 proteasomes. Most of them are involved in the ABA pathway and participate in anti-stress, such as XERICO and CaDSR1 [50,63]. However, it remains to be determined how E3 proteins are interacted with substrate proteins, whether they recognize substrate proteins with the same characteristics, and whether E3 ubiquitin ligase can modify substrate proteins by ubiquitin or poly-ubiquitin.…”

“…The Capsicum annuum ADIP1 interacting ring finger protein 1 (CaAIRF1) degrades Capsicum annuum Type 2C Protein Phosphatase (CaADP1) through the ubiquitination pathway by changing the sensitivity to ABA to improve drought resistance [61]. The Capsicum annuum drought sensitive RING finger protein 1(CaDSR1) exhibited E3 ligase activity and promoted CaDILZ1 expression through the 26S proteasome pathway to alter ABA content in the modulation of drought tolerance [63]. Capsicum annuum ABA sensitive RING finger E3 ligase 1 (CaASRF1) positively modulates ABA signaling via modulation of CaAIBZ1's stability to drought stress [62].…”

A pepper RING‐type E3 ligase, CaASRF1, plays a positive role in drought tolerance via modulation of CaAIBZ1 stability

“…The cell‐free degradation assay was performed as previously described (Lim et al ., ). Proteins were extracted using a buffer containing 5 m m DTT, 10 m m MgCl 2 , 0.1% Triton X‐100, 10 m m ATP, 25 m m Tris‐HCl (pH 7.5), 10 m m NaCl from 4‐week‐old plants of wild‐type and CaASRF1 ‐OX transgenic plant.…”

Characterization of the bZIP Transcription Factor Family in Pepper (Capsicum annuum L.): CabZIP25 Positively Modulates the Salt Tolerance

“…Transcripts of some bZIP genes such as CAbZIP1, CaAIBZ1, CaDILZ1, and CaBZ1/PPI1 were shown to be significantly induced by drought and salt stresses (Lee et al, 2002;Hwang et al, 2005;Moon et al, 2015;Joo et al, 2018;Lim et al, 2018). Moreover, several bZIP genes have also been reported to be involved in signaling pathways and biotic stimuli, including ABA, salicylic acid (SA), methyl jasmonic acid (JA), ethylene, and against pathogen defense (Lee et al, 2002;Lee B. J. et al, 2006;Lim et al, 2015;Joo et al, 2018;Lim et al, 2018). The most-studied pepper bZIP TF was CaBZ1/PPI1, which showed specific functional roles in response to abiotic/biotic stresses.…”