Abstract
As a subfamily of basic helix-loop-helix (bHLH) transcription factors, phytochrome-interacting factors (PIFs) participate in regulating light-dependent growth and development of plants. However, limited information is available about PIFs in pepper. In the present study, we identified six pepper PIF genes using bioinformatics-based methods. Phylogenetic analysis revealed that the PIFs from pepper and some other plants could be divided into three distinct groups. Motif analysis revealed the presence of many conserved motifs, which is consistent with the classification of PIF proteins. Gene structure analysis suggested that the CaPIF genes have five to seven introns, exhibiting a relatively more stable intron number than other plants such as rice, maize, and tomato. Expression analysis showed that CaPIF8 was up-regulated by cold and salt treatments. CaPIF8-silenced pepper plants obtained by virus-induced gene silencing (VIGS) exhibited higher sensitivity to cold and salt stress, with an obvious increase in relative electrolyte leakage (REL) and variations in the expression of stress-related genes. Further stress tolerance assays revealed that CaPIF8 plays different regulatory roles in cold and salt stress response by promoting the expression of the CBF1 gene and ABA biosynthesis genes, respectively. Our results reveal the key roles of CaPIF8 in cold and salt tolerance of pepper, and lay a solid foundation for clarifying the biological roles of PIFs in pepper and other plants.
Highlights
Plants have developed multiple signaling transduction processes for regulating growth and development, and modulating complex molecular mechanisms by driving transcriptional or translational changes in transcription factors under diverse environmental conditions (Haak et al, 2017; Yang et al, 2019)
Six phytochrome-interacting factors (PIFs) genes were identified from the pepper genome, which were designated as CaPIF1, CaPIF3, CaPIF4, CaPIF7a, CaPIF7b, and CaPIF8
The basic helix-loop-helix (bHLH) and APB domains were found in all six CaPIF proteins, with the exception of CaPIF7b, which contained an incomplete Helix2 in the bHLH domain (Table 1 and Figure 1)
Summary
Plants have developed multiple signaling transduction processes for regulating growth and development, and modulating complex molecular mechanisms by driving transcriptional or translational changes in transcription factors under diverse environmental conditions (Haak et al, 2017; Yang et al, 2019). PIF Genes in Pepper as acts as an essential environmental signal that participates in plant development and stress response. In Arabidopsis, most PIFs redundantly promote skotomorphogenesis partly by promoting cell elongation, and mutation of PIF1, PIF3, PIF4, and PIF5 (usually named as pifq) would result in a striking constitutive photomorphogenesis phenotype in the dark (Leivar et al, 2008; Shin et al, 2009; Leivar and Monte, 2014) Unlike that of these PIFs, mutation of PIF2 would lead to elongated hypocotyls and small cotyledons under continuous R and FR light, indicating that PIF2 acts as a positive regulator in photomorphogenesis (Luo et al, 2014). Our results provide important information for further revealing the role of CaPIFs in pepper
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