Weighted Correlation Network Analysis Mining Key Metabolites and Genes for Regulation of Root Growth and Secondary Metabolism of Astragalus membranaceus mongholicus

Background: Harvesting period is an important feature that not only affects the yield quality of Astragalus herbs but also the content of astragaloside IV and calycosin 7-O-β-D-glucopyranoside which are considered as the core indicators of the quality of Astragalus herbs. Herb yield and quality undergo rapid and substantial changes during the harvesting process. Part of enzymes and their encoding genes have been identified as potential candidates for the biosynthesis of herb quality-related triterpenoid saponins and isoflavonoids. However, wide gap still exists in the understanding of the pathways involving growth, development and biosynthesis of these two important active components in the roots of Astragalus. Methods: In this study, we used Astragalus roots as material to analyze its metabolome and transcriptome of herbs at harvesting stage. Result: The results indicated that changes in the harvesting period had a significant effect on the yield and quality of the herbs. Correlation of metabolome and RNA-seq results constructed using weighted gene co-expression network analysis (WGCNA) with herb growth and development indicated that the expression patterns of 19 hub metabolites (Oxamniquine, 4-ene-Valproic acid, Traumatic Acid, L-Histidinol, Salidroside, Temsavir, Retaspimycin, Isosakuranetin, etc.) and 16 structural genes with annotations (CNX2, talA, ABCF2, HIBCH, crtZ, etc.) had the highest connectivity with root growth and secondary metabolism of Astragalus. To search for potential regulatory genes related to root growth and development, we screened 54 relevant genes using 16 hub genes with annotations. The results advance the molecular basis of biosynthesis of secondary metabolites related to the harvesting period of Astragalus herbs, which can provide a theoretical basis for determining the regulatory mechanism of yield and quality.