An Analysis of the Potential Regulatory Mechanisms of Sophora Flower Development and Nutritional Component Formation Using RNA Sequencing

Abstract

Sophora flower (Huaihua) is the flower of Sophora japonica L., which is used in ethnic food and traditional medicine in China. Unfortunately, the molecular mechanism related to the nutritional quality and regulation of floral organ development has yet to be elucidated in Huaihua. To understand the molecular mechanism of the different developmental stages of Huaihua, this study evaluated the transcriptome analyses of five different developmental periods from Huaihua. A total of 84,699 unigenes were reassembled from approximate 50 million high-quality clean reads. The results showed that the phenylpropanoid biosynthesis, plant hormone signal transduction, starch and sucrose metabolism, and fatty acid elongation process pathways were strongly induced at different developmental stage genes in Huaihua. During this study, 394 differentially expressed genes (DEGs) were identified for further studies, which included 13 phenylpropanoid biosynthesis-related genes, 186 plant hormone signal transduction-related genes, and 195 starch and sucrose metabolism response genes. Regarding the peroxidase in the lignin synthesis pathway, CCoAOMT was significantly upregulated with the development of Huaihua. The enzyme genes in flavonoid synthesis, such as PAL, 4CL, flavonol reductase, and 3 GT, were significantly downregulated during Huaihua development. In addition, the results also indicated that the enrichment key genes in these pathways of Huaihua can be divided into two distinct parts at developmental stages. In the floral bud stage, flavonoid, auxin, and cytokine synthesis-related genes were highly expressed. In the mature bud and full flowering stage, the expression level of genes related to lignin, gibberellin, abscisic acid, and salicylic acid synthesis was high, while, for other genes related to flavonoid synthesis, it was lower. Furthermore, the DEGs in the starch and sucrose metabolism pathway were also significantly upregulated in the later stage of flower development. This study provides a preliminary and comprehensive assessment of the quality formation and flowering regulation mechanism in Sophora japonica L. by investigating the expression profiles of the critical flowering-related genes at different developmental stages. The results indicate that the regulatory genes in these key biological pathways could be crucial factors involved in Huaihua development, which can provide a reference and new insights with which to further understand the molecular mechanisms of flower development in Sophora japonica L.