Seed development shapes the diversity, succession, and functional potential of endophytic bacterial communities in Camellia oleifera

Camellia oleifera is a significant woody oil crop with considerable commercial, nutritional, and ecological importance. The developmental processes of seed endophytic bacterial populations are inadequately understood. This study used 16S rRNA high-throughput sequencing to analyze the diversity, community structure, and predicted functions of endophytic bacteria in C. oleifera seeds across four developmental stages: early fruit-set (YC1), young fruit (YC2), early mature (YC3), and late mature (YC4). A total of 907,440 raw reads were obtained, and 874,097 effective sequences were retained across 12 sequencing samples, which were taxonomically assigned to 41 phyla, 112 classes, 258 orders, 448 families, 994 genera, and 1,602 putative species-level ASVs. The predominant phyla were Proteobacteria, Firmicutes, Actinobacteriota, and Bacteroidota, with Pseudomonas , Methylobacterium-Methylorubrum , and the uncultured lineage 1174-901-12 as the prevalent taxa. Alpha- and beta-diversity analyses showed distinct stage-specific community succession: YC1-YC3 exhibited greater richness and diversity, whereas YC4 showed a decline in both. PICRUSt2-based prediction of COG functional categories showed that functions related to energy production and conversion (C), amino acid transport and metabolism (E), inorganic ion transport and metabolism (P), translation, ribosomal structure and biogenesis (J), and cell wall/membrane/envelope biogenesis (M) were relatively abundant. These results provide a microbiological foundation for comprehending seed development and identifying functional strains in C. oleifera .