The Basic Helix-Loop-Helix Transcription Factor SmbHLH1 Represses Anthocyanin Biosynthesis in Eggplant

Abstract

Many basic helix-loop-helix transcription factors (TFs) have been reported to promote anthocyanin biosynthesis in numerous plant species, but little is known about bHLH TFs that inhibit anthocyanin accumulation. In this study, SmbHLH1 from Solanum melongena was identified as a negative regulator of anthocyanin biosynthesis. However, SmbHLH1 showed high identity with SmTT8, which acts as a SmMYB113-dependent positive regulator of anthocyanin-biosynthesis in plants. Overexpression of SmbHLH1 in eggplant caused a dramatic decrease in anthocyanin accumulation. Only the amino acid sequences at the N and C termini of SmbHLH1 differed from the SmTT8 sequence. Expression analysis revealed that the expression pattern of SmbHLH1 was opposite to that of anthocyanin accumulation. Yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) assays showed that SmbHLH1 could not interact with SmMYB113. Dual-luciferase assay demonstrated that SmbHLH1 directly repressed the expression of SmDFR and SmANS. Our results demonstrate that the biological function of bHLHs in anthocyanin biosynthesis may have evolved and provide new insight into the molecular functions of orthologous genes from different plant species.

SmMYB113 Is a Key Transcription Factor Responsible for Compositional Variation of Anthocyanin and Color Diversity Among Eggplant Peels

“…Anthocyanins are the main phenolic compounds in eggplant peels. To explore the relationship between anthocyanin composition and color in eggplant, six eggplant cultivars representing all eggplant cultivar colors were examined ( Duan et al, 2021 ). As shown in Supplementary Figure 1A , the six peel colors covered lavender in No.…”

“…Six eggplant cultivars (Numbers 44, 64, 76, 108, 109, and 133) ( Duan et al, 2021 ) including five S. melongena and one Solanum aethiopicum (mainly cultivated and popular in Africa), and SmMYB113-OE transgenic eggplants were planted in the solar greenhouse at Shandong Agricultural University. Peels of the six eggplant cultivars and peels and pulps of SmMYB113-OE transgenic eggplants were harvested from nine representative fruits of each type in triplicate.…”

“…The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fpls.2022. 843996/full#supplementary-material Supplementary Figure 1 | Fruit colors and the relative anthocyanins content of the six eggplant cultivars (Duan et al, 2021). (A) Fruit colors of the six eggplant cultivars at the commodity maturity stage; (B) the relative anthocyanins content in the eggplant peel at fruit setting (fruiting), rapid growth period (growth), and commodity maturity stage (maturity).…”

“… Fruit colors and the relative anthocyanins content of the six eggplant cultivars ( Duan et al, 2021 ). (A) Fruit colors of the six eggplant cultivars at the commodity maturity stage; (B) the relative anthocyanins content in the eggplant peel at fruit setting (fruiting), rapid growth period (growth), and commodity maturity stage (maturity).…”

“…In this study, we report the metabolic profiles of flavonoids that may contribute to different pigmentation in eggplants. Six eggplant cultivars with different peel colors representing all possible eggplant colors were examined ( Duan et al, 2021 ). In addition, the anthocyanin composition of eggplant peels and pulps activated by transgenic overexpression of SmMYB113 were also investigated using metabolome technology.…”