Analysis of flavonoids and anthocyanin biosynthesis-related genes expression reveals the mechanism of petal color fading of Malus hupehensis (Rosaceae)

Abstract

Malus hupehensis (Pamp.) Rehder is an indigenous wild crabapple tree from China that has received increased attention, due to its significant ornamental and economical values. The flowers change from red to white during development, a phenomenon that is prevalent within Malus genus. However, there are no reports on the phytochemical aspects of M. hupehensis flower. Here, we investigated the mechanism of color fading through biochemical and molecular analysis of M. hupehensis petals during development. Sixteen flavonoids were detected, and cyanidin-3-galactoside was the major anthocyanin in petals. The levels of most compounds initially increased and then decreased during flower development. The changing profile of total anthocyanins was consistent with the changes in floral color. Analysis of anthocyanin biosynthesis-related genes showed that the expression levels of PAL, CHS, CHI, DFR, FLS, ANS, UFGT, MYB10 and MYB12 were significantly higher at early stages than at later stages, similarly to the change in cyanidin-3-galactoside contents. MYB10 and MYB12 significantly positively correlated with CHS, CHI and DFR. There was a particularly strong positive correlation between MYB10 and ANS, and MYB12 was strongly positively correlated with LAR. Thus, MYB10 appeared to regulate mainly anthocyanin biosynthesis, and MYB12 could influence the expression of multiple structural genes in both the anthocyanin and flavanol pathways. By contrast, MYB6, bHLH33 and WD40 were significantly and positively correlated with one another but negatively correlated with the levels of many compounds and most structural genes, indicating that these three transcription factors could regulate together anthocyanin biosynthesis. Our results revealed the information about the temporal and spatial regulation of anthocyanin biosynthesis in M. hupehensis and provide the diverse flower color intensities and patterning in Chinese crabapple.

Dynamic Changes of the Anthocyanin Biosynthesis Mechanism During the Development of Heading Chinese Cabbage (Brassica rapa L.) and Arabidopsis Under the Control of BrMYB2

“…For example, studies of ornamental crops mainly concentrate on the developing of their flowers and petals: five transcriptional factor genes— MiMYB1 , MibHLH1 , MibHLH2 , MiWDR1 , and MiWDR2 —were cloned from Matthiola incana , in which MiMYB1 interacted with MibHLH1 and MibHLH2 with their especially increased expression found in petals during floral buds’ development, accompanied by the upregulation of MiF3’H , MiDFR , MiANS , and Mi3GT as well as the accumulation of anthocyanins ( Nuraini et al, 2020 ). Malus hupehensis has a red-to-white coloration during its flower development and the involved fading mechanism is produced by the higher expression degrees of PAL , CHS , CHI , DFR , FLS , ANS , UFGT , MYB10 , and MYB12 at early red stages than at later white stages ( Han et al, 2020 ). In other work, flavonol content and FLS expression both increased prior to anthocyanin accumulation during floral development, but then decreased once anthocyanins were produced in lisianthus plants, accompanied by the essential upregulation of CHS , CHI , and F3H in both flavonol and anthocyanin biosynthesis throughout floral development and the high transcription of F3′5′H , DFR , and ANS in the late pigmentation stage ( Noda et al, 2004 ).…”

“…In addition to these positive regulators, existed negative regulators could also influence the regulation of anthocyanin biosynthesis, in that they suppress the transcription and expression of target genes by binding to specific DNA sequences of their promoter regions, thereby indirectly modulating protein–protein interactions or genes’ co-expression in the flavonoid synthesis pathway ( Han et al, 2020 ). For instance, the R3-MYBs ‘MYBL2’ and ‘CPC’ (CAPRICE), together with the lateral organ boundary domain (LBD) factors ‘LBD37,’ ‘LBD38,’ and ‘LBD39,’ are several well-studied negative regulators of anthocyanin biosynthesis in Arabidopsis , which repress anthocyanin biosynthesis either by suppressing the anthocyanin biosynthesis genes (ABGs) or by directly inhibiting the formation of MBW complexes ( Zhu et al, 2009 ; Dubos et al, 2010 ; Matsui et al, 2010 ; Chen et al, 2019 ).…”

How the Color Fades From Malus halliana Flowers: Transcriptome Sequencing and DNA Methylation Analysis

“…The samples were filtered through 0.45 μm filters and the phenolic compounds were analyzed using HPLC coupled with DAD; HPLC-diode array detector (HPLC-DAD) analysis was carried out using a Shimadzu LC-2030C liquid chromatograph (Shimadzu, Kyoto, Japan) equipped with an Inertsil C-18 column (5.0 μm particle size, 4.6 mm × 250 mm). The HPLC-DAD separation was performed as previously described by Han et al (2020) . The compound varieties were determined by comparing their retention times and UV spectral data with those of the known standards according to reported LC-MC and NMR spectroscopic results of Malus spp.…”

The Regulation of Floral Colour Change in Pleroma raddianum (DC.) Gardner

“…The flower colour is commonly related to the anthocyanin content in model plants such as petunia ( P. hybrida ) [ 28 ]. Moreover, anthocyanins accumulation was shown to be responsible for the coloured stages in the species whose corolla colour changes [ 4 , 5 , 6 , 12 , 13 , 14 ]. The results obtained here demonstrate that this is the case in P. raddianum , where petunidin and malvidin appear at the S3 stage together with the pink colour and are increased at the purple stage.…”

“…(Solanaceae) and Malus hupehensis (Pamp.) Rehder (Rosaceae) [ 8 , 14 ]. In B. calycina , the petals turn from dark purple to completely white within three days after anthesis, due to the reduction of anthocyanin concentration and increment of phenolic acid content during flower development [ 8 , 15 ].…”