Transcription factor CabHLH035 promotes cold resistance and homeostasis of reactive oxygen species in pepper

Plant basic helix -loop -helix (bHLH) transcription factors (TFs) play central roles in various abiotic stresses. However, its role in plant cold resistance is largely unknown. Previously, we characterised CaNAC035 in pepper, which positively regulates tolerance to cold, salt and drought stresses tolerance. Here, we identi fied CabHLH035, a CaNAC035-interacting protein in pepper. To explore its functions in cold stress tolerance, we silenced the gene in pepper via virus -induced gene silencing (VIGS) and overexpressed the gene in Arabidopsis. The results showed that CabHLH035 expression was induced by cold treatment, and silencing of CabHLH035 decreased cold stress tolerance. Conversely, overexpression of CabHLH035 in Arabidopsis increased cold stress tolerance. To investigate homologs genes of C -repeat binding factor (CBF) pathway proteins and reactive oxygen species (ROS) marker gene expression blocking by CabHLH035, we performed yeast one -hybrid (Y1H), dual luciferase and electrophoretic mobility shift assay experiments. The results showed that CabHLH035 bound to the region upstream of the CaCBF1A and CaAPX promoters. Additionally, CaCBF1A bound to the CaDHN4 promoter. Taken together, our results showed that CabHLH035 plays a crucial role in cold stress tolerance and its potential as a target for breeding cold -resistant crops. The findings provide a basis for studying the functions and regulatory network of cold stress tolerance in pepper.