Abstract
NAC (NAM, ATAF1/2, and CUC2) proteins are the plant-specific transcription factors (TFs) which are important in plant response to abiotic stresses. However, knowledge about the functional role that NACs play in pepper abiotic stress tolerance is limited. In this study, we isolated a NAC TF gene, CaNAC035, from pepper (Capsicum annuum L.), where the protein is localized in the nucleus and functions as a transcriptional activator. CaNAC035 expression is induced by low and high temperatures, osmotic stress, salt, gibberellic acid (GA), methyl-jasmonic acid (MeJA), salicylic acid (SA), and abscisic acid (ABA). To understand the function of CaNAC035 in the abiotic stress responsep, we used virus-induced gene silencing in pepper to knockdown the CaNAC035 and overexpressed the CaNAC035 in Arabidopsis. The results showed that pepper seedlings in which CaNAC035 was silenced, showed more damage than the control pepper plants after cold, NaCl, and mannitol treatments. Correspondingly increased electrolyte leakage, a higher level of malondialdehyde (MDA), H2O2, and superoxide radicals were found after cold treatments. CaNAC035-silenced seedlings exhibited lower chlorophyll content while CaNAC035-overexpressed Arabidopsis plants had higher germination rate and fresh weight after mannitol and NaCl treatments. We also reported 18 proteins that potentially interact with CaNAC035 and may participate in processes such as the stress response, resistance, and photosynthesis. Our results suggest that CaNAC035 is a positive regulator of abiotic stress tolerance in pepper which acts through multiple signaling pathways.
Highlights
As sessile organisms, plants are continuously exposed to adverse external stimuli during their life cycle
In order to identify the structural features of CaNAC035, we analyzed the sequences of CaNAC035 and predicted proteins from other species using DNAMAN software
The results showed that CaNAC035 consists of two parts, the highly variable C-terminal region (NAM domain) and the conserved N-terminal (Figure 1)
Summary
Plants are continuously exposed to adverse external stimuli during their life cycle. Transcription factors (TFs) are trans-acting proteins that act as molecular switches to regulate the expression of a variety of target genes by interacting with the cis-elements in the gene promoters (Singh et al, 2002). Most plant TFs belong to large gene families, such as WRKY, bZIP, NAC, AP2/ EREBP, and bHLH. Some TF family members are involved in the adaptive stress response, activating or inhibiting the expression of stress-related genes to alter the plant’s ability to adapt to stressful environments, while others help to coordinate the plants growth and development (Zhong et al, 2012). Members of the plant-specific NAC TF family [named for cup-shaped cotyledon (CUC2), Arabidopsis thaliana transcription activation factors (ATAF1/2), and no apical meristem (NAM)] are well known for their functional roles
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