Light and abscisic acid independently regulated FaMYB10 in Fragaria × ananassa fruit

Abstract

Light and ABA independently regulated anthocyanin biosynthesis via activation of FaMYB10 expression. FaMYB10 accelerated anthocyanin synthesis of pelargonidin 3-glucoside and cyanidin 3-glucoside during strawberry fruit ripening. Light is an integral factor in fruit ripening. Ripening in non-climacteric fruit is also effected by the plant hormone abscisic acid (ABA). However, how light and/or ABA regulate fruit ripening processes, such as strawberry color development remains elusive. Results of the present study showed light and ABA regulated strawberry fruit coloration via activation of FaMYB10 expression, an R2R3 MYB transcription factor. Light exposure increased FaMYB10 transcript levels, flavonoid pathway genes, and anthocyanin content. Exogenous ABA promoted FaMYB10 expression, and anthocyanin content, accompanied by increased ABA-responsive transcript levels and flavonoid pathway genes. ABA biosynthesis inhibitor treatment, and RNAi-mediated down-regulation of the ABA biosynthetic gene (9-cis epoxycarotenoid dioxygenase: FaNCED1), and ABA receptor (magnesium chelatase H subunit: FaCHLH/ABAR) showed inverse ABA effects. Furthermore, additive effects were observed in anthocyanin accumulation under combined light and ABA, indicating independent light and ABA signaling pathways. FaMYB10 down-regulation by Agrobacterium-mediated RNA interference (RNAi) in strawberry fruits showed decreased pelargonidin 3-glucoside and cyanidin 3-glucoside levels, accompanied by consistent flavonoid pathway gene expression levels. FaMYB10 over-expression showed opposite FaMYB10 RNAi phenotypes, particularly cyanidin 3-glucoside synthesis by FaMYB10, which was correlated with FaF3'H transcript levels. These data provided evidence that light and ABA promoted FaMYB10 expression, resulting in anthocyanin accumulation via acceleration of flavonoid pathway gene expression. Finally, our results suggested FaMYB10 serves a role as a signal transduction mediator from light and ABA perception to anthocyanin synthesis in strawberry fruit.

Differential Anthocyanin Concentrations and Expression of Anthocyanin Biosynthesis Genes in Strawberry ‘Sachinoka’ during Fruit Ripening under High-temperature Stress

“…Jeong et al (2004) reported that the accumulation of anthocyanins in grape fruit was enhanced by abscisic acid treatment and suppressed by naphthaleneacetic acid and shading. Kadomura-Ishikawa et al (2015a) suggested that light and abscisic acid independently regulate anthocyanin biosynthesis via activation of FaMYB10 expression in strawberry fruits. Azuma et al (2012) elucidated that the expression of other MYB-related genes in grape and of many flavonoid biosynthesis pathway genes was regulated independently by temperature and light.…”

“…Medina-Puche et al (2014) stated that FaMYB10 is not involved in the expression of ANS. Kadomura-Ishikawa et al (2015a) stated that FaMYB10 is deeply involved in UFGT expression. Our results agree with those studies.…”

“…The regulation of anthocyanin biosynthesis by MYB TFs has been studied using MYB cDNAs (Aharoni et al, 2001;Schaart et al, 2013;Kadomura-Ishikawa et al, 2015a). Transgenic tobacco transformed with FaMYB1 isolated from strawberry fruits showed a severe reduction in pigmentation and in the expression of late flavonoid biosynthesis genes, and FaMYB1 overexpression adversely affected the activities of the late flavonoid biosynthesis enzymes (Aharoni et al, 2001).…”

“…The regulation of their biosynthesis has been studied widely and frequently (review in Jaakola, 2013). In particular, UFGT (UDP-glucose: flavonoid 3-O-glucosyltransferase) plays an important role in anthocyanin biosynthesis in grape (Boss et al, 1996;Kobayashi, 2009), and FaMYB10 regulates the expression of FaUFGT in strawberry (Medina-Puche et al, 2014;Kadomura-Ishikawa et al, 2015a).…”

Evaluating the involvement and interaction of abscisic acid and miRNA156 in the induction of anthocyanin biosynthesis in drought-stressed plants

“…This led them to suggest that changes in the amount of endogenous ABA may play an important role in the induction of anthocyanin synthesis. Recently, it has been shown that treatments of Fragaria x ananassa fruits and Salvia miltiorrhiza hair roots with fluridone (an ABA biosynthetic inhibitor) resulted in a strong suppression of anthocyanin biosynthesis (Cui et al 2012;Kadomura-Ishikawa et al 2014). Hence, further previous evidence supports that ABA playing a direct or indirect role in the induction of anthocyanin biosynthesis under drought stress conditions.…”