Developmental Variation in Fruit Polyphenol Content and Related Gene Expression of a Red-Fruited versus a White-Fruited Fragaria vesca Genotype

Sutapa Roy,Douglas Archbold,Sanjay Singh

doi:10.3390/horticulturae4040030

Abstract

Two cultivars of F. vesca, red-fruited Baron Solemacher (BS) and white-fruited Pineapple Crush (PC), were studied to compare and contrast the quantitative accumulation of major polyphenols and related biosynthetic pathway gene expression patterns during fruit development and ripening. Developing PC fruit showed higher levels of hydroxycinnamic acids in green stages and a greater accumulation of ellagitannins in ripe fruit in comparison to BS. In addition to anthocyanin, red BS fruit had greater levels of flavan-3-ols when ripe than PC. Expression patterns of key structural genes and transcription factors of the phenylpropanoid/flavonoid biosynthetic pathway, an abscisic acid (ABA) biosynthetic gene, and a putative ABA receptor gene that may regulate the pathway, were also analyzed during fruit development and ripening to determine which genes exhibited differences in expression and when such differences were first evident. Expression of all pathway genes differed between the red BS and white PC at one or more times during development, most notably at ripening when phenylalanine ammonia lyase 1 (PAL1), chalcone synthase (CHS), flavanone-3′-hydroxylase (F3′H), dihydroflavonol 4-reductase (DFR), anthocyanidin synthase (ANS), and UDP:flavonoid-O-glucosyltransferase 1 (UFGT1) were significantly upregulated in the red BS fruit. The transcription factors MYB1 and MYB10 did not differ substantially between red and white fruit except at ripening, when both the putative repressor MYB1 and promoter MYB10 were upregulated in red BS but not white PC fruit. The expression of ABA-related gene 9-cis-epoxycarotenoid dioxygenase 1 (NCED1) was higher in red BS fruit but only in the early green stages of development. Thus, a multigenic effect at several points in the phenylpropanoid/flavonoid biosynthetic pathway due to lack of MYB10 upregulation may have resulted in white PC fruit.

Highlights

The accumulation of diverse polyphenols during strawberry (Fragaria spp.) fruit ripening, including flavonols, proanthocyanidins, and especially anthocyanins, is responsible for enhancing fruit nutritional value and providing some level of defense against insects and pathogens [1]
The polyphenolic compound levels measured at four consecutive developmental stages, G1, G2, T, and R, of red Baron Solemacher (BS) and white Pineapple Crush (PC) showed significant effects of genotype, stage of development, and their interaction on most phenolic group sums (Table 2)
The accumulation and distribution of polyphenols are governed by a metabolic network that is strongly connected to and co-regulated with the expression of structural and regulatory genes of the phenylpropanoid/flavonoid biosynthetic pathway [18,37,47,50,52]

Summary

Introduction

The accumulation of diverse polyphenols during strawberry (Fragaria spp.) fruit ripening, including flavonols, proanthocyanidins, and especially anthocyanins, is responsible for enhancing fruit nutritional value and providing some level of defense against insects and pathogens [1]. Most of the basic biosynthetic steps leading to phenylpropanoid/flavonoid biosynthesis in F. x ananassa are known [4,16], the regulation of these steps is not yet clearly established but are key to understanding metabolite flux and accumulation patterns. In F. chiloensis, a comparison of a red- versus white-fruited genotype indicated that the absence of anthocyanins in the white mutant was correlated with low expression of several flavonoid biosynthetic genes [17]. Several transcription factors (TFs) controlling the expression of the known phenylpropanoid/flavonoid biosynthetic genes have been identified in apple (Malus x domestica Borkh.) [18,19,20,21], grape (Vitis spp.) [22,23], peach and nectarine (Prunus persica) [24,25], and strawberry [15,26,27]. Higher expression of most anthocyanin-related genes in ABA-treated F. x ananassa berries was observed

Methods

Results

Conclusion