Objective To identify the genome-wide family members of type III polyketide synthase (PKS III) and conduct bioinformatics analysis and expression profile analysis and clarify the relationship between their expression and the content of active components of Huzhang (Polygonum cuspidatum). Methods Based on the genome data of P. cuspidatum, the members of PKS III gene family were identified. Subsequently, the characteristics of these members were analyzed, including the physicochemical properties of their encoded proteins, secondary structure, phylogeny, and conserved motifs. Transcriptome data were further used to analyze their expression profiles, and the correlation between the expression levels of these PKS III genes and the active components was investigated. Results A total of 73 PKS III members were identified in the whole genome of P. cuspidatum, which were unevenly distributed on 20 chromosomes. Subcellular localization prediction indicated that most PKS III members were localized in the cytoplasm, while a small portion were localized on the plasma membrane. Phylogenetic analysis revealed that they were clustered into three major groups, and members within the same group shared identical conserved domains. Analysis of promoter cis-acting elements demonstrated that the PKS III genes contained various elements responsive to hormones, light, and growth and development. Expression profile analysis showed significant differences in the expression of PKS III genes among five tissues of roots and rhizomes of P. cuspidatum. Specifically, the expression levels of PKS32 and PKS42 were significantly higher than those of other genes in all tissues, with the highest expression detected in the rhizome pith. Correlation analysis indicated that PKS3, PKS8, PKS21, PKS44, PKS58, and PKS61 exhibited a significant positive correlation with the contents of polydatin and physcion, and PKS27, PKS56, and PKS69 showed a significant positive correlation with the contents of resveratrol and emodin; and PKS32 and PKS42 displayed a significant positive correlation with the content of physcion. Conclusion A total of 73 PKS III family members were identified, and the expression levels of some members correlated significantly with the contents of active components in P. cuspidatum roots and rhizomes. This study provides a foundation for subsequent research on the functions of PKS III genes and for elucidating the biosynthetic mechanisms of anthraquinones, stilbenes, and flavonoids in P. cuspidatum.

Polygonum cuspidatum Sieb.et Zucc  /  gene family  /  polyketide synthase  /  bioinformatics analysis  /  gene expression  /  resveratrol  /  emodin