Differences in gene expression and endophytic bacterial diversity in Atractylodes macrocephala Koidz. rhizomes from different growth years

Atractylodes macrocephala Koidz. (AMK) is widely used in traditional Chinese medicine owing to its pharmacological activity. Here, we aimed to characterize the differentially expressed genes (DEGs) of one- and three-year growth (OYG and TYG) rhizomes of AMK, combined with endophytic bacterial diversity analysis using high-throughput RNA sequencing. A total of 114 572 unigenes were annotated using six public databases. In all, 3570 DEGs revealed a clear difference, of which 936 and 2634 genes were upregulated and downregulated, respectively. The results of KEGG pathway analysis indicated that DEGs corresponding to terpenoid synthesis gene were downregulated in TYG rhizomes. In addition, 414 424 sequences corresponding to the 16S rRNA gene were divided into 1267 operational taxonomic units (OTUs). Moreover, the diversity of endophytic bacteria changed with species in the OYG (773) and TYG (1201) rhizomes at the OTU level, and Proteobacteria, Actinobacteria, and Bacteroidetes were the dominant phyla. A comparison of species differences among different growth years revealed that some species were significantly different, such as Actinomycetes, Variovorax, and Cloacibacterium. Interestingly, the decrease in the function-related metabolism of terpenoids and polyketides was correlated with the low expression of terpene synthesis genes in TYG rhizomes, as assessed using PICRUSt2. These data provide a scientific basis for elucidating the mechanisms underlying metabolite accumulation and endophytic bacterial diversity in relation to the growth years in AMK.