Differential Functions of Pepper Stress-Associated Proteins in Response to Abiotic Stresses

Abstract

Stress-associated proteins (SAPs), a group of zinc-finger-type proteins, have been identified as novel regulators of plant abiotic and biotic stresses. However, although they have been discovered in different plant species, their precise functional roles remain unclear. Here, we identified 14 SAP subfamily genes in the pepper genome. An investigation of the promoter regions of these genes for cis-regulatory elements associated with abiotic stress responses revealed the presence of multiple stress-related elements. Domain and phylogenetic analyses using the corresponding protein sequences revealed that the CaSAP genes can be classified into six groups (I–VI) and sorted into two broad types. Expression levels of the CaSAP genes were found to be differentially induced by low temperature, the dehydration stress, or exogenous abscisic acid. Group II and IV genes were highly induced by the low temperature and dehydration treatments, respectively. Moreover, subcellular localization analysis indicated that the proteins in these two groups are distributed in the nucleus, cytoplasm, and plasma membrane. Among the pepper plants silenced with the three identified group II CaSAP genes, the CA02g10410-silenced plants showed tolerance to low temperature, whereas the CA03g17080-silenced plants were found to have temperature-sensitive phenotypes. Interestingly, group IV CaSAP-silenced pepper plants showed drought-tolerant phenotypes. These findings contribute to a preliminary characterization of CaSAP genes and provide directions for future research on the biological role of CaSAPs in response to different abiotic stresses.

Pepper stress‐associated protein 14 is a substrate of CaSnRK2.6 that positively modulates abscisic acid‐dependent osmotic stress responses

“…The accumulation of CaSAP14 transcripts was induced at 2 or 6 h post‐treatment. In addition, we extended our previous examination of the organ‐specific expression of CaSAP14 (Bae et al., 2021), which revealed that CaSAP14 expression was differentially induced in different pepper organs, with the highest levels being detected in petioles, flowers, and seeds (Figure 3b). In addition, we sought to determine the subcellular localization of CaSAP14 protein by transiently expressing GFP‐tagged CaSAP14 in the leaves of N. benthamiana plants.…”

“…Given the auto‐activity of full‐length CaSnRK2.6, we used a C‐terminal truncated CaSnRK2.6 fragment (amino acids 1–320: CaSnRK2.6 A320) for the purposes of Y2H screening and accordingly identified several interacting partner proteins, among which was CA10g19590, a protein annotated as a member of the SAP family. Previously, we isolated 14 SAP genes in C. annuum (Bae et al., 2021). In the present study, we named them, based on groups and the order of chromosomal loci within groups (CaSAP1, CA01g04040; CaSAP2, CA02g10410; CaSAP3, CA03g17080; CaSAP4, CA00g44110; CaSAP5, CA10g16510; CaSAP6, CA12g06430; CaSAP7, CA01g16220; CaSAP8, CA01g19950; CaSAP9, CA10g20690; CaSAP10, CA01g19980; CaSAP11, CA12g22410; CaSAP12, CA02g29220; CaSAP13, CA05g01100; CaSAP14, CA10g19590).…”

“…To determine the levels of CaSAP14 expression induced by different chemicals and abiotic stresses, we conducted reverse transcription‐quantitative polymerase chain reaction (RT‐qPCR) analysis using the pepper leaves subjected to mannitol, ABA, H 2 O 2 , dehydration, low temperature, or high‐salinity‐associated stresses (Figure 3a; Bae et al., 2021). The accumulation of CaSAP14 transcripts was induced at 2 or 6 h post‐treatment.…”

“…In this study, we identified and functionally characterized CaSAP14, one of the 14 known SAPs in pepper (Bae et al., 2021), as a potential candidate for CaSnRK2.6 substrate in response to exogenous ABA, dehydration, and high‐salinity stress. Given that CaSnRK2.6 has shown to function in the ABA‐dependent drought‐induced osmotic stress response (Lim, Baek, Lim, et al., 2021), we initially sought to verify the physical interaction between CaSnRK2.6 and the 14 pepper SAPs.…”

“…In our previous studies on the stress responses of pepper ( Capsicum annuum ), we isolated 14 CaSAPs and classified them into six groups (I–VI), which are differentially expressed in response to dehydration, mannitol, low temperature, and exogenous ABA (Bae et al., 2021). Among these, the group II and IV CaSAPs were established to play roles in low temperature and dehydration stress, respectively.…”