Abstract
Anthocyanins, as the most important chromogenic substances in flavonoids, are responsible for the red, purple, and blue coloration of flowers. Anthocyanins are synthesized in the cytoplasmic surface of the endoplasmic reticulum (ER) but accumulate predominantly in the vacuole, while glutathione S-transferases (GSTs) are considered to be mainly responsible for the transport process. Our previous studies showed that the expression of PsGSTF3 was positively correlated with anthocyanin content in tree peony tissues, which is a key candidate gene for anthocyanin accumulation. Here, we successfully cloned and characterized full-length PsGSTF3 containing three exons and two introns. Subcellular localization showed that PsGSTF3 was localized in the nucleus and ER membrane. Functional complementation of the Arabidopsis transparent testa19 (tt19) mutant indicated that PsGSTF3 was responsible for the transport of anthocyanins but not of proanthocyanidins (PAs). Virus-induced gene silencing (VIGS) of PsGSTF3 not only led to a decrease in anthocyanin accumulation but also caused a reduction of structural genes in the anthocyanin biosynthesis pathway (ABP) to varying degrees. Heterologous overexpression of PsGSTF3 was found to increase the anthocyanin accumulation in tobacco petals. Furthermore, the yeast two-hybrid (Y2H) assay showed that PsGSTF3 interacted with PsDFR, which together contributed to the coloration of petals. In conclusion, these results demonstrate that PsGSTF3 encodes an important GST transporter of anthocyanin in tree peony petals and provides a new perspective for the associated transport and regulatory mechanisms.
Highlights
Received: 23 December 2021Anthocyanins, as the most important chromogenic substances in flavonoids, are a group of water-soluble pigments responsible for the red, purple, and blue coloration of flowers, fruits, and leaves [1]
PsGSTF3 that was ectopically transformed brid (Y2H) experiment showed that PsGSTF3 interacted with PsDFR
Our results showed that PsGSTF3 contained glutathione S-transferases (GSTs)-conserved domains and conformed to the typical gene structure characteristics of the Phi subfamily
Summary
Received: 23 December 2021Anthocyanins, as the most important chromogenic substances in flavonoids, are a group of water-soluble pigments responsible for the red, purple, and blue coloration of flowers, fruits, and leaves [1]. The anthocyanin biosynthesis pathway (ABP) is one of the most thoroughly studied secondary metabolic pathways in plants, and is highly conserved [8]. The enzymes that catalyze anthocyanin biosynthesis include CHS (chalcone synthase), CHI (chalcone isomerase), F3H (flavanone 3-hydroxylase), F30 H (flavonoid 30 -hydroxylase), F30 50 H (flavonoid 30 ,50 hydroxylase), DFR (dihydroflavonol 4-reductase), ANS (anthocyanin synthase), and UFGT (UDP flavonoid glucosyltransferase). CHS, CHI, F3H, F30 H, and F30 50 H together comprise the early ABP [8,9], while DFR, ANS, and UFGT are all considered components of the late biosynthetic pathway [2,8,10,11]. Anthocyanin biosynthesis is regulated by the MYB-bHLH-WD40 (MBW) protein complex [10], which is composed of MYB and bHLH transcription factors (TFs) and a WD40 protein.
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