Abstract
Blueberry (Vaccinium spp.) is a popular healthy fruit worldwide. The health value of blueberry is mainly because the fruit is rich in anthocyanins, which have a strong antioxidant capacity. However, because blueberry is a non-model plant, little is known about the structural and regulatory genes involved in anthocyanin synthesis in blueberries. Previous studies have found that spraying 1,000 mg/L abscisic acid at the late green stage of “Jersey” highbush blueberry fruits can increase the content of anthocyanins. In this experiment, the previous results were verified in “Brightwell” rabbiteye blueberry fruits. Based on the previous results, the anthocyanin accumulation process in blueberry can be divided into six stages from the late green stage to the mature stage, and the transcriptome was used to systematically analyze the blueberry anthocyanin synthesis process. Combined with data from previous studies on important transcription factors regulating anthocyanin synthesis in plants, phylogenetic trees were constructed to explore the key transcription factors during blueberry fruit ripening. The results showed that ABA increased the anthocyanin content of blueberry fruits during veraison. All structural genes and transcription factors (MYB, bHLH, and WD40) involved in the anthocyanin pathway were identified, and their spatiotemporal expression patterns were analyzed. The expression of CHS, CHI, DFR, and LDOX/ANS in ABA-treated fruits was higher in the last two stages of maturity, which was consistent with the change in the anthocyanin contents in fruits. In general, six MYB transcription factors, one bHLH transcription factor and four WD40 transcription factors were found to change significantly under treatment during fruit ripening. Among them, VcMYBA plays a major role in the regulation of anthocyanin synthesis in ABA signaling. This result preliminarily explained the mechanism by which ABA increases the anthocyanin content and improves the efficiency of the industrial use of blueberry anthocyanins.
Highlights
Blueberry belongs to the genus Vaccinium, and the main cultivated species are northern highbush blueberry plants (Vaccinium corymbosum L.), southern highbush blueberry, lowbush blueberry (V. angustifolium Aiton), and rabbiteye blueberry (V. ashei Reade) (Leisner et al, 2017)
The application of exogenous ABA in the late green period of blueberry fruit maturation resulted in an increase in anthocyanins
The most direct reason for this result is that chalcone synthase (CHS), chalcone isomerase (CHI), dihydroflavonol 4-reductase (DFR), and LDOX/anthocyanidin synthase (ANS) are highly expressed at S5–S6
Summary
Blueberry belongs to the genus Vaccinium, and the main cultivated species are northern highbush blueberry plants (Vaccinium corymbosum L.), southern highbush blueberry (primarily V. corymbosum L.), lowbush blueberry (V. angustifolium Aiton), and rabbiteye blueberry (V. ashei Reade) (Leisner et al, 2017). Blueberry fruit is one of the most popular healthy fruits worldwide. This popularity is mainly because blueberries contain a variety of phytonutrients, the most representative of which are anthocyanins (Borges et al, 2010). With the in-depth study of blueberry anthocyanins, a growing number of clinical and animal experiments have proven that blueberry anthocyanins can effectively alleviate obesity (Prior et al, 2010) and cardiovascular disease (Zhu et al, 2013) and prevent type 2 diabetes (BurtonFreeman et al, 2019) and cancer (Faria et al, 2010). The content and variety of anthocyanins are important characteristics of blueberry fruit. This study systematically explored the key transcription factors in anthocyanin synthesis and laid a foundation for future molecular breeding
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