Skin Browning and Expression of PPO, STS, and CHS Genes in the Grape Berries of ‘Shine Muscat’

Abstract

A recently popular Japanese yellow-green-skin table grape, 'Shine Muscat' (Vitis labruscana Bailey × V. vinifera L.), has the problem of berry skin browning, which occurs at the maturation stage just before harvest. Tiny reddish-brown blotches appear on the surface of berries and considerably decrease the grape's market value. Although the mechanisms and factors for browning are unknown, we hypothesized the involvement of polyphenol compounds and their oxidation reactions. In this study, the gene expressions of polyphenol oxidase (PPO), stilbene synthase (STS), and chalcone synthase (CHS), which are key enzymatic genes related to the metabolic pathway for polyphenols, were analyzed during berry maturation to examine the molecular basis for browning. Skin browning occurred on several berries in a bunch of 'Shine Muscat' from 80 days after full bloom (DAFB), after which the number of berries with skin browning increased, and the browned area spread on the berry surfaces with maturation. Increases in the expression of VvPPO2, VvSTS type B, and VvCHS1 were associated with skin browning, and the trans-resveratrol content also increased in the browning skin, suggesting that biosynthesis and metabolic pathways for phenolic compounds were activated at the time of browning. In terms of VvPPO genes, specific up-regulation of VvPPO2 expression was observed compared with the VvPPO1 gene. The promoter sequence of VvPPO2 contains more Myb binding motifs and W-box motifs than does VvPPO1. The specific up-regulation of VvPPO2 gene expression will play a crucial role in understanding and managing the skin-browning mechanism in the grape berries of 'Shine Muscat'.

Effects of Abscisic Acid/Ethephon Treatments on Berry Development and Maturation in the Yellow-green Skinned ‘Shine Muscat’ Grape

“…The resveratrol content was determined using an Ultra-Fast Liquid Chromatography (UFLC) system (Prominence UFLC LC-20AD; Shimadzu Co., Kyoto, Japan) equipped with a degasser (DGC-20 A3), an auto sampler (SIL-20AC HT), a column oven (CTO-20A), a diode array detector (SPD-M20A), and a 50 × 3.0-mm Inertsil ODS-3 column (GL Science, Tokyo, Japan). The extracts were analyzed using a previously described UFLC procedure (Suehiro et al, 2014).…”

“…The expression levels of target genes were quantified by real-time quantitative reverse transcription PCR (qRT-PCR) using a TaKaRa Thermal Cycler Dice device (TP8000; TaKaRa Bio Inc.) as described in our previous study (Suehiro et al, 2014). Primer sets were prepared for the following polyphenol biosynthesisrelated genes: phenylalanine ammonia-lyase (PAL) genes (Sparvoli et al, 1994); chalcone synthase (CHS) genes (Suehiro et al, 2014); stilbene synthase (STS) genes (Henanff et al, 2009); polyphenol oxidase (PPO) genes (Suehiro et al, 2014); VvMYB14 and VvMyb15 genes that encode Myb-like transcription factors involved in stilbene biosynthesis (Höll et al, 2013) and phytohormone-related genes: the 9-cis-epoxycarotenoid dioxygenase (NCED)1 and NCED2 genes, which encode enzymes that are involved in ABA biosynthesis (Speirs et al, 2013); type 2C protein phosphatase (PP2C) genes, which encode negative regulators of ABA signaling (Boneh et al, 2012;Gambetta et al, 2010); 1-aminocyclopropane-1-carboxylate oxidase (ACO) genes from the ethylene biosynthesis pathway (Muñoz-Robredo et al, 2013); the ethylene insensitive 3 family protein (EIN3) gene, which encodes a transcription factor in the ethylene signaling pathway (Chervin and Deluc, 2010); the GA 2-oxidase (GA2ox), GA3ox, and GA20ox from the GA biosynthesis pathway (Giacomelli et al, 2013); the gibberellic acid insensitive (GAI)1 gene, which encodes a transcription factor with a DELLA domain that is involved in GA signaling (Boss and Thomas, 2002); the gibberellininsensitive dwarf 1 (GID1) gene, which encodes one of the GA receptors (Acheampong et al, 2015); the cytokinin histidine kinase receptors (CHKs) genes, which encode membrane-bound homodimeric proteins that are involved in cytokinin signaling (Böttcher et al, 2015); the VvYUC1 gene, which encodes a key enzyme that is involved in auxin biosynthesis (Böttcher et al, 2013a); and the auxin response factor (ARF)1 gene, which encodes a transcription factor that is involved in auxin signaling (Wan et al, 2014). Primer sets for the VvPALs, VvPP2Cs, VvGA2ox, VvGA20ox, VvGA3ox, VvGAI1, VvGID1, and VvCHKs genes were generated for this study using DNA sequence information ob-tained from previous studies (Acheampong et al, 2015;Boneh et al, 2012;Boss and Thomas, 2002;Böttcher et al, 2015;Giacomelli et al, 2013;…”

“…Because skin browning was also severe after ethephon treatments, the increase in VvPPO2 expression level is probably more closely associated with browning. Previous studies have shown that VvPPO2 plays a role in skin browning (Katayama-Ikegami et al, 2017;Suehiro et al, 2014), and the expression of PPO genes can be induced in response to biotic and abiotic stresses (Taranto et al, 2017;Yan et al, 2017). ABA can also mediate plant defense responses (Vishwakarma et al, 2017).…”

“…Unfortunately, this crop is susceptible to skin browning, a physiological disorder known as "Kasuri-sho" in Japanese. "Kasuri-sho" usually occurs during berry maturation, approximately 70-80 days after full bloom (DAFB) (Mochida et al, 2013;Suehiro et al, 2014). Skin browning markedly decreases the market value of the product.…”

Estimation of Changes in Mechanical and Color Properties from the Weight Loss Data of “Shine Muscat” Fruit during Storage

“…Because skin color is important for consumer acceptability of table grapes, the color characteristics of several grape cultivars were investigated [6]. In fact, the color of Shine Muscat fruit at the preharvesting stage was previously investigated [8,9]; however, the changes in color properties of the fruit during storage were not investigated. e objective of this study was to identify the changes in mechanical and color properties of Shine Muscat fruit during storage.…”