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Glutaredoxins (GRXs) are a widely distributed group of small oxidoreductases that play an important role in responding to oxidative stress and maintaining redox homeostasis in living organisms. However, there has been no report on the GRX gene family in tea plants (Camellia sinensis). In this study, we conducted a systematic analysis of the CsGRX gene family in tea plants and identified a total of 86 CsGRX genes. Based on phylogenetic and conserved active site analyses, these genes were classified into four categories: CC-type, CPYC-type, CGFS-type, and GRL-type. These subtypes showed distinct characteristics in terms of gene structure, conserved motif, chromosome distribution, subcellular localization, cis-regulatory elements, and expression pattern, indicating functional differences among CsGRX family members. Collinearity analysis showed that the CsGRX family may have undergone member expansion using tandem and segmental duplication along with overwhelmingly strict purifying selection. Protein tertiary structure analysis supported the conserved site-specific binding of CsGRX family members to glutathione. Protein interaction network analysis revealed that CsGRX may interact with glutathione reductase (GR), 2-Cys Peroxiredoxin BAS1, TGA3, and others to participate in the oxidative stress response in tea plants. GO and KEGG enrichment analyses also supported the important role of the CsGRX family in maintaining intracellular redox homeostasis. Expression analysis based on RNA-seq revealed differential expression patterns of CsGRX genes under drought, cold stress, and in different tissues, which were further confirmed by RT-qPCR analysis, indicating their broad-spectrum functionality. This study provides a new perspective for further exploring the evolution and molecular functions of specific CsGRX genes. [ABSTRACT FROM AUTHOR]

Tea is one of the most popular non-alcoholic beverages globally. The leaves of the tea plants serve as the raw materials for tea production, making tea tree cultivation widespread as an economically significant tree species. Nonexpressor of pathogenesis-related genes 1 (NPR1) is a key regulator of the salicylic acid (SA) signaling pathway, playing a significant role in the plant's response to biotic and abiotic stresses. However, the NPR1-like gene family in tea plants remains elusive. This study aims to systematically analyze the NPR1-like gene family in tea plants. Four CsNPR1-like genes were identified and categorized into three branches based on phylogenetic analysis. Collinearity analysis demonstrated conservation of the NPR1-like gene across different species. Analysis of cis-regulatory elements suggested that CsNPR1-like genes may be involved in various hormonal and stress responses. Protein structure analysis revealed that the CsNPR1-likes exhibited typical ANK and BTB/POZ structural domains. The protein interaction network identified various known and novel NPR1-interacting proteins, including the TGA transcription factor, which was further confirmed in planta. Meta-analysis of transcriptome data indicated that CsNPR1-like genes had spatiotemporal expression patterns and were induced by drought and cold stresses. Additionally, CsNPR1a activates the accumulation of the acidic SA-dependent pathogenic-associated protein PR1 but not the basic chitinase (PR3) in a transient expression assay. This study provides comprehensive information for investigating the NPR1-like gene family in tea plants. [ABSTRACT FROM AUTHOR]

The phytochrome-interacting factors (PIFs) proteins belong to the subfamily of basic helix–loop–helix (bHLH) transcription factors and play important roles in chloroplast development and chlorophyll biosynthesis. Currently, knowledge about the PIF gene family in Camellia sinensis remains very limited. In this study, seven PIF members were identified in the C. sinensis genome and named based on homology with AtPIF genes in Arabidopsis thaliana. All C. sinensis PIF (CsPIF) proteins have both the conserved active PHYB binding (APB) and bHLH domains. Phylogenetic analysis revealed that CsPIFs were clustered into four groups—PIF1, PIF3, PIF7, and PIF8—and most CsPIFs were clustered in pairs with their corresponding orthologs in Populus tremula. CsPIF members in the same group tended to display uniform or similar exon–intron distribution patterns and motif compositions. CsPIF genes were differentially expressed in C. sinensis with various leaf colors and strongly correlated with the expression of genes involved in the chlorophyll metabolism pathway. Promoter analysis of structural genes related to chlorophyll metabolism found DNA-binding sites of PIFs were abundant in the promoter regions. Protein–protein interaction networks of CsPIFs demonstrated a close association with phytochrome, PIF4, HY5, TOC1, COP1, and PTAC12 proteins. Additionally, subcellular localization and transcriptional activity analysis suggested that CsPIF3b was nuclear localized protein and possessed transcriptional activity. We also found that CsPIF3b could activate the transcription of CsHEMA and CsPOR in Nicotiana benthamiana leaves. This work provides comprehensive research of CsPIFs and would be helpful to further promote the regulation mechanism of PIF on chlorophyll metabolism in C. sinensis. [ABSTRACT FROM AUTHOR]