Analysis of Differential Mechanisms in Flavonoid Synthesis in the Exocarp of virescens and nigrescens Fruits and Development of KASP Molecular Markers
Background An oil palm. It is an important tropical woody oilseed crop. The fruit contains a relatively high proportion of flavonoids, which are of great nutritional value and have antioxidant, anti - inflammatory effects, and antibacterial functions. The means by which flavonoids are biosynthesized in oil palm is unclear. This study applied LC-MS/MS and RNA-Seq technologies to find out the molecular regulatory mechanism of flavonoids in oil palm exocarp. The exocarps of virescens (FS) and nigrescens (FT) at 95d, 125d, and 185d after pollination were used as experimental materials so as to measure and analyze the metabolome and transcriptome of oil palm exocarps at different developmental stages. The study proposed to find the types of flavonoid metabolites, key synthetic genes, and biological metabolic pathways in oil palm exocarp.Results A total of 274 flavonoids were found in FS, and 275 in FT. In the course of the three developmental stages, the flavonoids in FT were more abundant than in FS. FS had a bigger proportion of flavonoid components, whereas FT contained more anthocyanin components. The differentially expressed metabolites were mainly found in three pathways: flavonoid biosynthesis, flavone and flavonol biosynthesis, and anthocyanin biosynthesis. By analyzing metabolomics and transcriptomics together, the flavonoid biosynthetic pathway was put together, and enzyme genes and metabolites involved in flavonoid synthesis were obtained. In the case of FS, six enzyme genes such as HCT-2, DFR-1, C3'H and seven differential metabolites for example Trifolin, Prunin, Vitexin are involved. For FT, eight enzyme genes such as HCT-1, F3H-1, ANR and nine metabolites, say Isovitexin, Flavosativaside, Baimaside, are involved. The research was able to develop 9 pairs of KASP molecular markers (K2-K10). In the field, they were used to verify how well genotypes and corresponding phenotypes of 30 FS plants and 30 FT plants matched, with an accuracy of 100%. The 9 pairs of these markers are closely linked to the EgDFR gene and can successfully tell FS and FT apart.Conclusions The study gives a theoretical basis for getting clear about the flavonoid synthesis mechanism in the exocarp of oil palm fruits and breeding high - flavonoid oil palm varieties in the future.