Inhibits Anthocyanin Biosynthesis Research Articles

Ethylene mediates the branching of the jasmonate-induced flavonoid biosynthesis pathway by suppressing anthocyanin biosynthesis in red Chinese pear fruits.

SummaryFlavonoid accumulation in most fruits is enhanced by ethylene and jasmonate. However, little is known about the hormone functions related to red pear fruit coloration or their combined effects and potential underlying mechanisms. Various treatments were used to investigate the flavonoid metabolite profile and pear transcriptome to verify the effects of ethylene and jasmonate on flavonoid biosynthesis in red pear fruits as well as the mechanism behind this. Ethylene inhibits anthocyanin biosynthesis in red Chinese pear fruits, whereas jasmonate increases anthocyanin and flavone/isoflavone biosyntheses. The branching of the jasmonate‐induced flavonoid biosynthesis pathway is determined by ethylene. Co‐expression network and Mfuzz analyses revealed 4,368 candidate transcripts. Additionally, ethylene suppresses PpMYB10 and PpMYB114 expression via TF repressors, ultimately decreasing anthocyanin biosynthesis. Jasmonate induces anthocyanin accumulation through transcriptional or post‐translational regulation of TFs‐like MYB and bHLH in the absence of ethylene. However, jasmonate induces ethylene biosynthesis and the associated signalling pathway in pear, thereby decreasing anthocyanin production, increasing the availability of the precursors for flavone/isoflavone biosynthesis and enhancing deep yellow fruit coloration. We herein present new phenotypes and fruit coloration regulatory patterns controlled by jasmonate and ethylene, and confirm that the regulation of fruit coloration is complex.

Inhibition of post-transcriptional gene silencing of chalcone synthase genes in petunia picotee petals by fluacrypyrim.

In petals of picotee petunia (Petunia hybrida) cultivars, margin-specific post-transcriptional gene silencing (PTGS) of chalcone synthase A (CHSA) inhibits anthocyanin biosynthesis, resulting in marginal white tissue formation. In this study, we found that a low molecular mass compound, fluacrypyrim, inhibits PTGS of CHSA, and we explored the site-specific PTGS mechanism of operation. Fluacrypyrim treatment abolished the picotee pattern and eliminated site-specific differences in the levels of anthocyanin-related compounds, CHSA expression, and CHSA small interfering RNA (siRNA). In addition, fluacrypyrim abolished the petunia star-type pattern, which is also caused by PTGS of CHSA. Fluacrypyrim treatment was effective only at the early floral developmental stage and predominantly eliminated siRNA derived from CHS genes; i.e. siRNA derived from other genes remained at a comparable level. Fluacrypyrim probably targets the induction of PTGS that specifically operates for CHS genes in petunia picotee flowers, rather than common PTGS maintenance mechanisms that degrade mRNAs and generate siRNA. Upon treatment, the proportion of colored tissue increased due to a shift of the border between white and colored sites toward the margin in a time- and dose-dependent manner. These findings imply that the fluacrypyrim-targeted PTGS induction is completed gradually and its strength is attenuated from the margins to the center of petunia picotee petals.

Map-based cloning of the pear gene MYB114 identifies an interaction with other transcription factors to coordinately regulate fruit anthocyanin biosynthesis.

Red fruits are popular and widely accepted by consumers because of an enhanced appearance and enriched anthocyanins. The molecular mechanism of anthocyanin regulation in red-skinned pear (Pyrus) has been studied, and the genes encoding the biosynthetic steps and several transcription factors (TFs) have been characterized. In this study, a candidate R2R3 MYB TF, PyMYB114, was identified by linkage to the quantitative trait loci (QTL) for red skin color on linkage group 5 in a population of Chinese pear (Pyrus bretschneideri). The function of PyMYB114 was verified by transient transformation in tobacco (Nicotinana tabacum) leaves and strawberry (Fragaria) and pear fruits, resulting in the biosynthesis of anthocyanin. Suppression of PyMYB114 could inhibit anthocyanin biosynthesis in red-skinned pears. The ERF/AP2 TF PyERF3 was found to interact with PyMYB114 and its partner PybHLH3 to co-regulate anthocyanin biosynthesis, as shown by a dual luciferase reporter system and a yeast two-hybrid assay. In addition, the transcript abundance of PyMYB114 and PyMYB10 were correlated, and co-transformation of these two genes into tobacco and strawberry led to enhanced anthocyanin biosynthesis. This interaction network provides insight into the coloration of fruits and the interaction of different TFs to regulate anthocyanin biosynthesis.

Effects of methyl jasmonate and abscisic acid on anthocyanin biosynthesis in callus cultures of red-fleshed apple (Malus sieversii f. niedzwetzkyana)

We researched the effects of methyl jasmonate, abscisic acid, and a combination of the two on anthocyanin metabolism in callus material induced from the leaves of a red-fleshed apple individual, which was a hybrid offspring of Malus sieversii f. niedzwetzkyana and Malus domestica cv. ‘Fuji’. The results showed that methyl jasmonate promoted anthocyanin accumulation with increasing methyl jasmonate concentration in the range of 10−6 to 10−3 mol/L. Abscisic acid significantly inhibited anthocyanin biosynthesis, and its inhibitory effect was highest at 6 μmol/L among all treatments. In addition, methyl jasmonate alleviated the inhibitory effect of abscisic acid on anthocyanin biosynthesis. Gene expression analysis indicated that methyl jasmonate induced the expression of MdMYB9 and MdMYB10, which are positive regulator of anthocyanin biosynthesis, and inhibited MdMYB11 expression. It also upregulated the expression of the anthocyanin structural genes MdCHS, MdF3H and MdUFGT. Abscisic acid inhibited the expression of MdMYB3 and MdMYB10, as well as the expression of the structural genes MdF3H, MdDFR, MdLDOX and MdUFGT. Methyl jasmonate relieved the inhibition by abscisic acid by decreasing the expression of MdMYB11 and MdMYB16, and increasing the expression of the anthocyanin regulatory genes MdMYB3, MdMYB9 and MdMYB10, and the structural genes MdCHS, MdDFR, MdF3H and MdUFGT. Thus, we elucidated the roles of methyl jasmonate and abscisic acid in the regulation of anthocyanin production at the gene transcription level.

Transcriptome profiling reveals auxin suppressed anthocyanin biosynthesis in red-fleshed apple callus (Malus sieversii f. niedzwetzkyana)

Anthocyanin biosynthesis in callus culture in vitro is strongly influenced by exogenous auxin concentrations. However, the mechanisms by which auxin regulates anthocyanin biosynthesis are largely unknown. To understand the molecular basis of this phenomenon, global gene expression was analyzed in red-fleshed apple calli treated with 1-naphthaleneacetic acid (NAA; 0.3 and 10 mg/L) and 2,4-dichlorophenoxyacetic acid (2,4-D; 0.03 and 0.6 mg/L) using RNA-seq. A total of 3070 and 2533 genes were differently expressed (log2 ratio ≥ 2 at P < 0.0001) in the 2,4-D and NAA treatments, respectively. Thereof, 937 genes were up-regulated and 902 genes were both down-regulated. Genes involved in anthocyanin and flavonoid synthesis and transport into the vacuole were generally down-regulated. Higher concentrations of 2,4-D and NAA facilitated the transport of auxin and induced the expressions of genes involved in the homeostatic feedback regulatory loop. In the auxin signaling pathway, nine Aux/IAA family genes and seven ARF family genes were up-regulated. Moreover, 298 transcription factors were differentially expressed in the NAA and 2,4-D treatments. Among them, some members of MYB, bHLH, and WD40 families that directly regulate anthocyanin and flavonoid synthesis, such as MYB75 (MdMYB10), MYB12, MYB111, MYB113, TT2, and TT8 (MdbHLH3), were down-regulated by NAA and 2,4-D. Auxin also affected gene expression in other plant hormone signaling pathways, such as the cytokinin, ethylene, and gibberellic acid pathways, which also influenced anthocyanin biosynthesis. This study provides a valuable overview of transcriptome changes and gives insight into the molecular mechanism by which auxin inhibits anthocyanin biosynthesis in red-fleshed apple calli.

Effect of auxin, cytokinin and nitrogen on anthocyanin biosynthesis in callus cultures of red-fleshed apple (Malus sieversii f.niedzwetzkyana)

We have induced callus tissues from one R6/R6 homozygous genotype red-fleshed apple individual which was the hybrid offspring of Malus sieversii f.niedzwetzkyana and ‘Fuji’, and investigated the effect of auxin alone and auxin combined with cytokinin or nitrogen deficiency on anthocyanin synthesis. In callus culture, auxin alone significantly inhibited anthocyanin biosynthesis with the increase of auxin concentration. The inhibitory effect of 2,4-dichlorophenoxyacetic acid (2,4-D) on anthocyanin accumulation was about tenfold stronger than naphthalene acetic acid. Anthocyanin regulatory genes (MdMYB10 and MdbHLH3) and structural genes were dramatically suppressed by 0.6 mg/L 2,4-D. The inhibitory effect of auxin on anthocyanin biosynthesis was influenced by cytokinins 6-benzylaminopurine (BAP) and thidiazuron (TDZ) as well as nitrogen deficiency. Auxin and cytokinin displayed the interaction in controlling anthocyanin biosynthesis. Co-treatment of auxin and cytokinin (BAP or TDZ) significantly enhanced the cytokinin-induced increase in anthocyanin levels but too high auxin concentration strongly inhibited anthocyanin synthesis even in the presence of cytokinin. Nitrogen deficiency could reverse the inhibition of anthocyanin accumulation by auxin.

Effect of Epibrassinolide on Pigment Content, Total Protein Amount and Peroxidase Activity in Excised Cucumber Cotyledons

ABSTRACTBrassinosteroids (BRs) are a group of plant steroids that are known to elicit remarkable growth responses such as growth, seed germination, rhizogenesis, senescence, flowering, abscission, maturation, and also confer resistance on plants against various abiotic stresses. Brassinosteroids increase chlorophyll breakdown and inhibit anthocyanin biosynthesis. In this study the effect of epibrassinolide (epi-BL) on pigment content, soluble protein content, and peroxidase (POD) activity was investigated in excised cotyledons of cucumber seedlings. The cucumber seedlings were grown in dark conditions for 9 days and then their etiolated cotyledons were harvested. After that, they were transferred into Petri dishes containing 10−7 mol/L, 10−9 mol/L and 10−11 mol/L epi-BL. Cotyledons were incubated for 14 h in the dark at room temperature, then they were incubated in light for 3 h. Results showed that epi-BL affected the chlorophyll and carotenoid content, but no significant changes were observed when compared with the control.

RNA silencing in white petunia flowers creates pigmentation patterns invisible to the human eye

Modern commercial petunias exhibit a wide range of flower colors, which can be observed in gardens. In this study, we present a petunia cultivar that exhibits a floral pattern that is invisible to humans but is possibly visible to pollinating insects. We show that this hidden pattern is established by differentially localized accumulation of flavonols and cinnamic acid derivatives in the corolla limb. This accumulation is caused by a combination of two distinct mechanisms that inhibit anthocyanin biosynthesis: a loss-of-function mutation in the ANTHOCYANIN2, and localized RNA-silencing of CHALCONE SYNTHASE-A.

Elevated temperature inhibits anthocyanin biosynthesis in the tepals of an Oriental hybrid lily via the suppression of LhMYB12 transcription

High temperature often reduces the quality of anthocyanin colour in flowers, which is a problem in the commercial production of ornamental plants. Anthocyanins are the predominant pigments in flowers of the Oriental hybrid lily (Lilium spp.). We investigated the effects of elevated temperature on anthocyanin accumulation in the tepals of a pink-flowered cultivar Marrero. To clarify the flower stage most susceptible to elevated temperature, the flowers were divided into seven developmental stages. Potted plants with flowers at these stages were incubated at 35°C or 20°C for 2 days. The elevated temperature at 35°C caused poor colouration in the tepals at stage (St) 2 and 3. At 20°C, anthocyanin accumulation began at St 2 and anthocyanin content increased at St 3. The elevated temperature did not affect anthocyanin colouration at other stages. To clarify the mechanism for the poor colouration at St 2 and 3 at 35°C, the transcription of LhMYB12 (which regulates anthocyanin biosynthesis), chalcone synthase (CHS), flavanone 3-hydroxylase (F3H), and dihydroflavonol 4-reductase (DFR) as well as endogenous sugar content was evaluated in tepals. The transcription of LhMYB12, CHS, F3H, and DFR was suppressed at St 2 and 3 under the elevated temperature. The change in sugar content in the tepals at 35°C was not correlated with the reduced anthocyanin accumulation. Thus, we conclude that elevated temperatures inhibit anthocyanin biosynthesis at St 2 and 3 via the suppression of LhMYB12 transcription.

Arabidopsis R2R3-MYB transcription factor AtMYB60 functions as a transcriptional repressor of anthocyanin biosynthesis in lettuce (Lactuca sativa).

The MYB transcription factors play important roles in the regulation of many secondary metabolites at the transcriptional level. We evaluated the possible roles of the Arabidopsis R2R3-MYB transcription factors in flavonoid biosynthesis because they are induced by UV-B irradiation but their associated phenotypes are largely unexplored. We isolated their genes by RACE-PCR, and performed transgenic approach and metabolite analyses in lettuce (Lactuca sativa). We found that one member of this protein family, AtMYB60, inhibits anthocyanin biosynthesis in the lettuce plant. Wild-type lettuce normally accumulates anthocyanin, predominantly cyanidin and traces of delphinidin, and develops a red pigmentation. However, the production and accumulation of anthocyanin pigments in AtMYB60-overexpressing lettuce was inhibited. Using RT-PCR analysis, we also identified the complete absence or reduction of dihydroflavonol 4-reductase (DFR) transcripts in AtMYB60- overexpressing lettuce (AtMYB60-117 and AtMYB60-112 lines). The correlation between the overexpression of AtMYB60 and the inhibition of anthocyanin accumulation suggests that the transcription factorAtMYB60 controls anthocyanin biosynthesis in the lettuce leaf. Clarification of the roles of the AtMYB60 transcription factor will facilitate further studies and provide genetic tools to better understand the regulation in plants of the genes controlled by the MYB-type transcription factors. Furthermore, the characterization of AtMYB60 has implications for the development of new varieties of lettuce and other commercially important plants with metabolic engineering approaches.

Induction of soybean vegetative storage proteins and anthocyanins by low-level atmospheric methyl jasmonate.

Soybean seedlings were exposed to atmospheric methyl jasmonate (MJ) to determine if low levels of this compound could regulate the expression and accumulation of the vegetative storage proteins (VSPs) in soybeans. Low levels of atmospheric MJ induced the accumulation of three VSPs with molecular masses of 27 kDa, 29 kDa, and 94 kDa (vsp27, vsp29, and vsp94, respectively). Atmospheric MJ caused vsp94 to be accumulated in all above-ground organs of the seedling uniformly after just 3 days of exposure. vsp27 preferentially accumulated in shoot tips and primary leaves, whereas vsp29 preferentially accumulated in the cotyledons. In addition to these effects, MJ also induced the biosynthesis of anthocyanins in light-grown seedlings but inhibited anthocyanin biosynthesis in etiolated seedlings. It is concluded that low levels of atmospheric MJ regulate anthocyanin biosynthesis and the organspecific accumulation of VSPs in developing soybean seedlings. The organ-specific differential accumulation may reflect changes in the pattern of nitrogen partitioning between various compounds and/or organs. These results lend substance to the hypothesis that volatile MJ may act as a gaseous messenger or growth regulator in plants.