TGA (TGACG motif-binding factor) proteins are plant-specific group D basic leucine zipper (bZIP) transcription factors that bind as-1/TGACG elements. TGA proteins regulate salicylic acid (SA)-dependent transcription and have context-dependent roles in jasmonic acid (JA)-related defense, growth, development and stress responses. Tea (Camellia sinensis) and oil tea (Camellia oleifera) are Theaceae crops grown for beverages and edible oil, and anthracnose, drought and chilling reduce their yield and quality. Although tea bZIP genes, including group D TGA members, have been cataloged, a comparative, family-wide analysis of TGA genes across representative Theaceae genomes and their cultivar-dependent responses to anthracnose has not been reported. We therefore identified TGA genes genome-wide in six representative Theaceae species: Camellia chekiangoleosa, C. oleifera, C. sinensis, Camellia crapnelliana, Camellia japonica and Stewartia sinensis. Arabidopsis thaliana was included as a reference species. We then examined their phylogeny, gene structure and conserved motifs, codon usage, duplication and collinearity, and promoter cis-elements. Public expression data for 32 TGA genes from C. sinensis, C. oleifera and C. chekiangoleosa were analyzed across tissues and under salt, drought and cold treatments, and a pericarp transcriptome dataset from the resistant ‘MY53’ and susceptible ‘MY01’ C. oleifera genotypes was reanalyzed after inoculation with Colletotrichum fructicola. The survey identified 68 non-redundant TGA genes (10–13 per species), each with intact bZIP and DOG1 domains and predicted nuclear localization. Phylogenetic analysis resolved five groups, and Theaceae members clustered mainly in Groups II and IV, where motif composition and exon–intron structure were conserved. Codon usage bias was weak (effective number of codons: 52–54; codon adaptation index: 0.77–0.80). For 27 within-species paralogous TGA pairs, Ka/Ks distributions remained below 1 (range of 0.046–0.429), and no pair exceeded the Ks > 2 saturation criterion, indicating purifying selection. In the current duplication classification, 6–11 of the 10–13 TGA genes per species were assigned to WGD- or segmental-duplication classes, but family sizes remained similar to A. thaliana (10 genes); the data therefore do not indicate substantial net family expansion. Promoters were enriched in cis-elements responsive to light, JA, SA and abscisic acid (ABA). Expression varied between tissues, and several genes were enriched in fruit and leaves. Salt, drought and cold each induced a subset of TGA genes. The 12 ColeTGA genes resolved into four cultivar-dependent expression patterns; ColeTGA3 and ColeTGA2 showed stronger increases in the resistant ‘MY53’ genotype, whereas ColeTGA7 increased in both genotypes. Together, these comparisons clarify how TGA genes have been conserved and how they diverged among the six sampled Theaceae species.

TGA (TGACG motif-binding factor) proteins are plant-specific group D basic leucine zipper (bZIP) transcription factors that bind as-1/TGACG elements. They integrate jasmonic acid (JA) and salicylic acid (SA) signaling with growth, development and stress responses. Tea (Camellia sinensis) and oil tea (Camellia oleifera) are Theaceae crops grown for beverages and edible oil, and anthracnose, drought and chilling reduce their yield and quality. TGA genes had not been characterized in either crop. We therefore identified TGA genes ge-nome-wide in six representative Theaceae species: Camellia chekiangoleosa, C. oleifera, C. sinensis, Camellia crapnelliana, Camellia japonica and Stewartia sinensis. We then examined their phylogeny, gene structure and conserved motifs, codon usage, duplication and col-linearity, and promoter cis-elements. Transcriptome data and qRT-PCR provided expres-sion evidence for C. oleifera TGA (ColeTGA) genes after inoculation with Colletotrichum fruc-ticola. The survey yielded 68 non-redundant TGA genes, 10 to 13 per species, each with in-tact bZIP and DOG1 domains and a predicted nuclear localization. Phylogenetic analysis resolved five groups, and Theaceae members clustered mainly in Groups II and IV, where motif composition and exon–intron structure were conserved. Codon usage bias was weak (effective number of codons 52–54; codon adaptation index 0.77–0.80). The mean Ka/Ks was 0.25, indicating purifying selection. Whole-genome and segmental duplication drove most family expansion (60–91.67%), while tandem duplication was rare. Promoters were enriched in cis-elements responsive to light, JA, SA and abscisic acid (ABA). Expres-sion varied among tissues, and several genes were enriched in fruit and leaves. Salt, drought and cold each induced subsets of TGA genes. After inoculation with C. fructicola, the 12 ColeTGA genes showed four expression patterns. ColeTGA2, ColeTGA3, ColeTGA4, ColeTGA6, ColeTGA10 and ColeTGA12 were strongly activated. Together, these compari-sons clarify how TGA genes have been conserved and how they diverged among Theaceae lineages. They also identify candidates for functional tests of anthracnose resistance and for stress-tolerance breeding in tea and oil tea.

Salt stress restricts tea production by causing Na⁺ accumulation in leaves, disrupting K⁺ homeostasis, and elevating ROS levels. In Camellia, the CHX genes that may counteract these effects remain poorly defined. Using a 14-genome panel, we identified 436 CHX genes and grouped them into 26 orthologous gene groups (OGGs), including 18 core, 2 soft-core, and 6 shell. A tea-only reference captured only part of this structure; three OGGs present in 7-12 genomes were absent from tea. At the family level, dispersed and tandem duplications were the most frequent duplication classes, whereas soft-core and shell genes showed distinct duplication profiles. Among 377 high-confidence gene pairs, 98.4% had Ka/Ks values below 1, indicating that purifying selection predominates across the family. Unexpectedly, core pairs had higher Ka/Ks values than dispensable pairs. Expression analysis showed that most CHX genes were expressed at low levels across tissues. Salt treatment induced six low-abundance genes, and qRT-PCR highlighted CsCHX.CR008, CsCHX.CR012, CsCHX.SH006, and CsCHX.CR017 as priority candidates for salt-tolerance studies. Collectively, this pan-genome-scale study establishes an evolutionary framework for the CHX family in the genus Camellia, showing that duplication, presence–absence variation, copy-number variation, and conservation class are associated with distinct salt-responsive expression patterns. These findings provide genomic resources and valuable insights for dissecting CHX function and supporting future breeding efforts toward improved salt tolerance in Camellia.