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.

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.