Kiwifruit (Actinidia chinensis) is a kind of nutritious fruit with a good commercial value. In recent years, kiwifruit roots and fruits have been found to have good medicinal properties. Although previous studies have investigated the function of some metabolites in kiwifruit, few have elucidated the differences in the metabolites between the root and fruit among different representative varieties.

Researchers from Wuhan Botanical Garden conducted a metabolomic analysis on the roots and different varieties of red, green, and yellow kiwifruit flesh. The results of the PCA analysis showed that the root could be separated from fruit samples, based on the differences in the metabolites.

In total, 410 metabolites were identified in the fruit and root tissues, 54 differentially expressed metabolites were shared between the root and each fruit sample, 17 of them were detected in the flavonoid pathway.

Four differential metabolites, including three flavonols (kaempferol-3-rhamnoside, L-Epicatechin and trifolin) and one dihydrochalcone (phloretin) were identified, which were highly rich in roots of kiwifruit. Phloretin can block tumor cell growth and induce apoptosis, and flavonols are beneficial for cardiovascular and cerebrovascular diseases. Therefore, flavonols and phloretin may be crucial components in the root of kiwifruit in traditional Chinese medicine.

The genes related to flavonols and dihydrochalcones were highly expressed in root, and four candidate structural genes (AcC4H, AcCHS, AcF3’H, and AcCCO) and three genes of transcription factors (AcRAP2-4, AcAP2-4 and AcbHLH62) were identified. The results of the RT-qPCR analysis showed that AcC4H, AcCHS, AcF3’H, AcCCO, AcRAP2-4 and AcAP2-4 had a significantly higher expression in the roots than in the fruits, while AcbHLH62 showed extremely low expression in roots.

The study determined the differences in the metabolites between the roots and fruits of different kiwifruit varieties, and identified candidate genes related to functional metabolites in flavonoid biosynthesis pathway. The differences in the metabolite profiles between roots and fruits and the variation among kiwifruit varieties facilitate the application of kiwifruit in the field of pharmacy and processing.

Results have been published in International Journal of Molecular Sciences entitled “Comprehensive Analysis of Metabolome and Transcriptome in Fruits and Roots of Kiwifruit”.

The regulatory network of flavonoid biosynthesis (Image by WBG)