Fujun Bu

Endophytic microorganisms play important roles in plant health, but their diversity and functions can vary with host developmental stage. Camellia oleifera, a major oil-producing crop in China, offers a valuable system for exploring these dynamics. We compared endophytic microbial communities in young (5-year) and old (15-year) C. oleifera leaves using high-throughput 16 S rRNA and ITS sequencing, supported by culture-dependent isolation and inhibition assays. Diversity indices, taxonomic composition, and predicted bacterial functions were analyzed with QIIME2 and PICRUSt2. Ten fungal and nine bacterial strains were isolated and tested for antagonism against key leaf pathogens in confrontation assays (n = 3 replicates). A total of 607 bacterial and 778 fungal ASVs were identified. Young leaves contained greater bacterial richness and diversity (Observed ASVs, Shannon, Simpson indices, P < 0.05), while old leaves hosted higher fungal richness. Beta diversity (Bray–Curtis PCoA) showed clear separation of bacterial communities by leaf age, with weaker separation for fungi. Bacterial functional prediction revealed enrichment of carbohydrate metabolism and amino acid biosynthesis in young leaves, while secondary metabolism and stress response pathways were more prominent in old leaves. Among isolated strains, Coniochaeta velutina inhibited Colletotrichum gloeosporioides, Alternaria alternata, and Botryosphaeria dothidea by 67.4%, 54.8%, and 65.2%, respectively. The bacterium Burkholderia ambifaria achieved the highest inhibition rate of 87.2% against B. dothidea. These findings suggest that leaf age shapes endophytic microbial diversity and bacterial functional potential in C. oleifera. Moreover, C. velutina and B. ambifaria represent promising candidates for biocontrol applications. While limited by small sample size (n = 3 replicates), this exploratory study provides foundational insights into age-associated shifts in endophyte communities and their biocontrol potential.

The Cysteine-rich polycomb-like protein (CPP) gene family encodes transcription factors that function as key regulators in various plant processes, including growth, development, and responses to environmental stresses. However, systematic analysis of this gene family in Theaceae plants remains limited. In this study, we comprehensively identified and analyzed the CPP gene family in six Theaceae species, revealing a total of 65 members that were phylogenetically classified into two distinct subfamilies. Multiple sequence alignment revealed that all CPP proteins contain conserved CXC domains (C1 and C2) and an intervening R motif. Gene structure analysis indicated that Class II genes are more conserved, with a predominant structure of 8 exons (71% of members). In contrast, Class I genes most contained 10 exons (48.4%). Codon usage bias analysis identified two distinct groups: 22 codons with high usage frequency and 42 with low usage. Collinearity analysis suggested that whole-genome duplication was the primary driver of the expansion of the CPP gene family, with no tandem duplications detected. A total of 82 types of cis-regulatory elements were identified, with stress-responsive elements being the most abundant. Transcriptome analysis showed that Class I CPP genes, such as CsinCPP2 , CcheCPP1 , and ColeCPP12 , had high expression in leaves, apical buds, and stems. Several Class II CPP genes, such as ColeCPP1 , CsinCPP9 , ColeCPP2 , and CcheCPP8 , were significantly upregulated in multiple stress. qRT-PCR expression profiling under drought and salt stress in Camellia oleifera yielded results consistent with the transcriptome data. This study provides a comprehensive and detailed analysis of the CPP gene family in Theaceae, offering valuable insights into the evolutionary dynamics and functional diversification of these genes.