RNAi-mediated silencing and overexpression of the FaMYB1 gene and its effect on anthocyanin accumulation in strawberry fruit

Abstract

Strawberry (Fragaria × ananassa) contains anthocyanins, which are important secondary metabolites and key contributors to the antioxidant capacity and nutritional value of the fruit. Anthocyanin biosynthetic genes have been identified. However, the detailed mechanism responsible for anthocyanin accumulation and regulation of biosynthetic genes during strawberry fruit ripening remain unclear. In the present study, we examined the effect of a Fragaria × ananassa myeloblastosis 1 homolog, FaMYB1, on anthocyanin accumulation in the strawberry fruit receptacle. Expression analysis shows that FaMYB1 transcripts increased in response to irradiance but not to abscisic acid treatments. Down-regulation of FaMYB1 was achieved in planta using Agrobacterium-mediated RNA interference (RNAi). As a result, FaMYB1-RNAi fruits exhibited a significant increase in anthocyanin content. Conversely, overexpression of FaMYB1 resulted in a decrease in anthocyanin content. Overexpression of FaMYB1 also significantly reduced expression of genes encoding anthocyanidin synthase and flavonoid glycosyltransferase, whereas downregulation of FaMYB1 resulted in a significant decrease in the amount of transcripts of leucoanthocyanidin reductase. These data suggest that FaMYB1 might negatively control anthocyanin biosynthesis in the strawberry fruit at the branching-point of anthocyanin/proanthocyanidin biosynthesis.

FaMYB44.2, a transcriptional repressor, negatively regulates sucrose accumulation in strawberry receptacles through interplay with FaMYB10

“…We monitored the changes in expression of important genes encoding regulatory proteins associated with fruit development and ripening, such as FaMRLK47 , FaSnRK2.6 , FaMYB1 , FaMYB10 , and FaMADS9 , as well as hormone-related genes ( Aharoni et al , 2001 ; Seymour et al , 2011 ; Medina-Puche et al , 2014 ; Lin-Wang et al , 2014 ; Feng, 2015 ; Han et al , 2015 ; Kadomura-Ishikawa et al , 2015 ; Jia et al , 2017 ; Fig. 4B ).…”

“…Studies investigating fruit ripening in strawberry have mainly focused on the mechanisms regulating anthocyanin accumulation ( Jiang and Joyce, 2003 ; Medina-Puche et al , 2014 ; Lin-Wang et al , 2014 ; Kadomura-Ishikawa et al , 2015 ). Several important regulatory proteins involved in anthocyanin accumulation have been identified, such as the protein kinases FaSnRK2.6 and FaMRLK47 and the transcription factors FaMYB1 and FaMYB10 ( Aharoni et al , 2001 ; Medina-Puche et al , 2014 ; Lin-Wang et al , 2014 ; Han et al , 2015 ; Kadomura-Ishikawa et al , 2015 ; Jia et al , 2017 ). We recently found that FaMRLK47, a negative regulator of anthocyanin accumulation, also functions as a positive regulator of sugar accumulation and that two important structural genes involved in sucrose accumulation, FaSPS3 (sucrose-6-phosphate synthase 3, gene31122 ) and FaSUS1 (sucrose synthase 1, gene12940 ), are key structural genes downstream of FaMRLK47 ( Jia et al , 2017 ).…”

“…In strawberry, MYB transcription factors comprise a large family, including 111 MYB proteins and 61 MYB-related proteins ( Zheng et al , 2016 ). The functions of most MYBs in strawberry are unclear, but several are involved in regulating proanthocyanin, flavonoid, and anthocyanin accumulation in fruits ( Aharoni et al , 2001 ; Medina-Puche et al , 2014 ; Lin-Wang et al , 2014 ; Kadomura-Ishikawa et al , 2015 ). FaMYB10 and FaMYB1 function as positive and negative regulators of anthocyanin and flavonoid accumulation, respectively, and FaMYB10 and FaMYB1 might couple with FabHLH3/33 ( gene08231 / gene19321 ) and/or FaTTG1 (WD40 protein, gene12450 ) to form a ternary MBW complex that regulates anthocyanin and flavonoid accumulation ( Schaart et al , 2013 ).…”

Comparative Transcriptome Analysis of Genes Involved in Anthocyanin Biosynthesis in Red and Green Walnut (Juglans regia L.)

“…In strawberry, FaMYB10 acts as an activator, whereas FaMYB1 acts as a repressor of anthocyanin biosynthesis, and both are expressed at high levels during the fruit ripening stage [ 67 , 68 ]. Pear PpMYB10 (previously misassigned as PyMYB10 ) contributes to the red pigmentation of colored pear fruits [ 69 ]. In this study, a candidate MYB ( Jrgene32450 ) showed higher expression in the leaf and peel of red walnut than in the leaf and peel of green walnut during the fruit ripening stage.…”

RNA interference targeting CYP76AH1 in hairy roots of Salvia miltiorrhiza reveals its key role in the biosynthetic pathway of tanshinones

“…RNAi is considered to be a potent reverse genetic tool for the identification of gene functions in plants. It was successfully implemented in the opium poppy [17], maize [18], and cotton [19], and was used to regulate the biosynthesis of target compounds and exert signal control in different plant tissues including leaves [20], seeds [21], fruits [22] and hairy roots [23]. Silencing of SmCPS1 with RNAi resulted in decreased accumulation of tanshinones in Danshen hairy roots, which verified the key role of SmCPS1 in tanshinone biosynthesis [11].…”