Characterization of Flavan-3-ols and Expression of MYB and Late Pathway Genes Involved in Proanthocyanidin Biosynthesis in Foliage of Vitis bellula.

Yue Zhu,Qing-Zhong Peng,Ci Du,De-Yu Xie,Ke-Gang Li

doi:10.3390/metabo3010185

Abstract

Proanthocyanidins (PAs) are fundamental nutritional metabolites in different types of grape products consumed by human beings. Although the biosynthesis of PAs in berry of Vitis vinifera has gained intensive investigations, the understanding of PAs in other Vitis species is limited. In this study, we report PA formation and characterization of gene expression involved in PA biosynthesis in leaves of V. bellula, a wild edible grape species native to south and south-west China. Leaves are collected at five developmental stages defined by sizes ranging from 0.5 to 5 cm in length. Analyses of thin layer chromatography (TLC) and high performance liquid chromatography-photodiode array detector (HPLC-PAD) show the formation of (+)-catechin, (−)-epicatechin, (+)-gallocatechin and (−)-epigallocatechin during the entire development of leaves. Analyses of butanol-HCl boiling cleavage coupled with spectrometry measurement at 550 nm show a temporal trend of extractable PA levels, which is characterized by an increase from 0.5 cm to 1.5 cm long leaves followed by a decrease in late stages. TLC and HPLC-PAD analyses identify cyanidin, delphinidin and pelargonidin produced from the cleavage of PAs in the butanol-HCl boiling, showing that the foliage PAs of V. bellula include three different types of extension units. Four cDNAs, which encode VbANR, VbDFR, VbLAR1 and VbLAR2, respectively, are cloned from young leaves. The expression patterns of VbANR and VbLAR2 but not VbLAR1 and VbDFR follow a similar trend as the accumulation patterns of PAs. Two cDNAs encoding VbMYBPA1 and VbMYB5a, the homologs of which have been demonstrated to regulate the expression of both ANR and LAR in V. vinifera, are also cloned and their expression profiles are similar to those of VbANR and VbLAR2. In contrast, the expression profiles of MYBA1 and 2 homologs involved in anthocyanin biosynthesis are different from those of VbANR and VbLAR2. Our data show that both ANR and LAR branches are involved in PA biosynthesis in leaves of V. bellula.

Highlights

Proanthocyanidins (PAs), known as condensed tannins, are oligomeric or polymeric flavan-3-ols
We report characterization of main flavan-3-ols and molecular properties of PA extension units as wells as gene expression involved in the late pathways in leaves of V. bellula (Figure 2a)
We focus on gene expression analysis of late pathway genes (VbDFR, VbANR, VbLAR1 and VbLAR2) of PA biosynthesis

Summary

Introduction

Proanthocyanidins (PAs), known as condensed tannins, are oligomeric or polymeric flavan-3-ols. The routine consumption of PAs from food and drink products, such as green tea, grape and cranberry, can prevent people from cancer, cardiovascular and aging diseases [1,2]. A great number of research efforts over the past many years have demonstrated that oligomeric PAs and their monomers such as (+)-catechin and (−)-epicatechin are one main group of flavonoid metabolites in red and white wines and form main beneficial substance [11,12,13,14,15]. The uptake of PAs and flavan-3-ols from wine or grape juice products can generally prevent human being from cardiovascular diseases, such as heart diseases, atherosclerosis, ischemic reperfusion injury, and lowering low density lipoprotein (LDL) levels [9,13,16,17]. When rats were fed with PAs, their hearts were shown a high resistance to myocardial ischemia reperfusion injury [17]

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Conclusion