Anthocyanins In Tubers Research Articles

Yield performance and anthocyanin content of several purple-fleshed sweet potato clones grown in two locations in East Nusa Tenggara, Indonesia

Abstract. Arsa IGBA, Mau YS, Ndiwa ASS, Gandut YRY, Ishaq LF, Mahayasa INW. 2024. Yield performance and anthocyanin content of several purple-fleshed sweet potato clones grown in two locations in East Nusa Tenggara, Indonesia. Biodiversitas 25: 2276-2289. Several promising purple-fleshed sweet potato hybrid clones were identified to have high yield potential and, thus, can be evaluated for other superior traits and later be further processed for varietal registration and release. This study aimed to determine the tuber yield performance and anthocyanin content of several purple-fleshed sweet potato clones across two locations and to identify the best clones based on mean performance and stability. The study was conducted in the farmer's field in two different altitudes in West Timor, i.e., Mata Air Village, Kupang District (86 masl) and Netpala Village, Timor Tengah Selatan (TTS) District (1,090 masl) from April to September 2023. Six purple-fleshed sweet potato clones/varieties were assigned as treatment. The experiment was laid out in a complete block design in each location, and each treatment consisted of three replicates. Observed data included fresh storage root yield, number of storage roots per plant, storage root length, storage root tuber diameter, and tuber anthocyanin content. Observed data from the two trial locations were subjected to a combined ANOVA, cluster analysis, Principal Component Analysis (PCA), and GGE biplot analysis. The results showed that the genotype-by-location interaction effect was significant in all studied traits. Meanwhile, location or genotype significantly affected all traits except for the location, which did not significantly affect the anthocyanin content. The storage root yield ranged from ~19.95 t ha-1 to ~49.33 t ha-1, while the anthocyanin content ranged from ~28,64 mg/100 g to ~157,65 mg/100 g. The ranks of the tested genotypes based on the mean performance and stability are Undana UJ 7>Undana UJ 1>JPV-1>Antin 3>Undana UJ 6>Undana UJ 3 for storage root yield and JPV-1>Antin 3>Undana UJ 7>Undana UJ 6>Undana UJ 3>Undana UJ 1 for anthocyanin content.

Enhanced UV-B Radiation in Potato Stems and Leaves Promotes the Accumulation of Anthocyanins in Tubers.

Enhanced ultraviolet-B (UV-B) radiation promotes anthocyanin biosynthesis in leaves, flowers and fruits of plants. However, the effects and underlying mechanisms of enhanced UV-B radiation on the accumulation of anthocyanins in the tubers of potatoes (Solanum tuberosum L.) remain unclear. Herein, reciprocal grafting experiments were first conducted using colored and uncolored potatoes, demonstrating that the anthocyanins in potato tubers were synthesized in situ, and not transported from the leaves to the tubers. Furthermore, the enhanced UV-B radiation (2.5 kJ·m-2·d-1) on potato stems and leaves significantly increased the contents of total anthocyanin and monomeric pelargonidin and peonidin in the red-fleshed potato '21-1' tubers, compared to the untreated control. A comparative transcriptomic analysis showed that there were 2139 differentially expressed genes (DEGs) under UV-B treatment in comparison to the control, including 1724 up-regulated and 415 down-regulated genes. The anthocyanin-related enzymatic genes in the tubers such as PAL, C4H, 4CL, CHS, CHI, F3H, F3'5'H, ANS, UFGTs, and GSTs were up-regulated under UV-B treatment, except for a down-regulated F3'H. A known anthocyanin-related transcription factor StbHLH1 also showed a significantly higher expression level under UV-B treatment. Moreover, six differentially expressed MYB transcription factors were remarkably correlated to almost all anthocyanin-related enzymatic genes. Additionally, a DEGs enrichment analysis suggested that jasmonic acid might be a potential UV-B signaling molecule involved in the UV-B-induced tuber biosynthesis of anthocyanin. These results indicated that enhanced UV-B radiation in potato stems and leaves induced anthocyanin accumulation in the tubers by regulating the enzymatic genes and transcription factors involved in anthocyanin biosynthesis. This study provides novel insights into the mechanisms of enhanced UV-B radiation that regulate the anthocyanin biosynthesis in potato tubers.

Methylation level of potato gene OMT30376 regulates tuber anthocyanin transformations.

After anthocyanin synthesis, a variety of anthocyanin compounds are produced through further methylation, glycosylation, and acylation. However, the effect of the potato methylase gene on anthocyanin biosynthesis has not been reported. Red and purple mutation types appear in tubers of the potato cultivar ‘Purple Viking’ with chimeric skin phenotypes. In this study, transcriptome and anthocyanin metabolome analyses were performed on skin of Purple Viking tubers and associated mutants. According to the metabolome analysis, the transformation of delphinidin into malvidin-3-O-glucoside and petunidin 3-O-glucoside and that of cyanidin into rosinidin O-hexoside and peonidin-3-O-glucoside were hindered in red tubers. Expression of methyltransferase gene OMT30376 was significantly lower in red tubers than in purple ones, whereas the methylation level of OMT30376 was significantly higher in red tubers. In addition, red skin appeared in tubers from purple tuber plants treated with S-adenosylmethionine (SAM), indicating the difference between purple and red was caused by the methylation degree of the gene OMT30376. Thus, the results of the study suggest that the OMT30376 gene is involved in the transformation of anthocyanins in potato tubers. The results also provide an important reference to reveal the regulatory mechanisms of anthocyanin biosynthesis and transformation.

Anthocyanins in Solanum tuberosum: A review

Anthocyanins are positively charged molecules of plant origin belonging to the flavonoid group, found in various pigmented varieties of Solanum tuberosum. The 6 most common anthocyanins found in potatoes are derivatives of pelargonidin, malvidin, petunidin, delphinidin, cyanidin and peonidin, in different concentrations. The distribution of anthocyanins in tubers is not uniform but differs between the skin and flesh, and it is associated with the distribution and intensity of colour. The anthocyanin content and antioxidant activity in Solanum tuberosum may vary with the genotype, environmental conditions, storage and the way of cooking the tubers, such as steaming or frying. Various properties of anthocyanins that are beneficial for humans have been studied, such as antioxidant, antitumor and antiviral properties. Several studies have shown that anthocyanins activate antioxidant systems in the liver, prevent the growth of colon cancer tumour cells, among other cancers.

StMYB44 negatively regulates anthocyanin biosynthesis at high temperatures in tuber flesh of potato.

High temperatures are known to reduce anthocyanin accumulation in a number of diverse plant species. In potato (Solanum tuberosum L.), high temperature significantly reduces tuber anthocyanin pigment content. However, the mechanism of anthocyanin biosynthesis in potato tuber under heat stress remains unknown. Here we show that high temperature causes reduction of anthocyanin biosynthesis in both potato tuber skin and flesh, with white areas forming between the vasculature and periderm. Heat stress reduced the expression of the R2R3 MYB transcription factors (TFs) StAN1 and StbHLH1, members of the transcriptional complex responsible for coordinated regulation of the skin and flesh pigmentation, as well as anthocyanin biosynthetic pathway genes in white regions. However, the core phenylpropanoid pathway, lignin, and chlorogenic acid (CGA) pathway genes were up-regulated in white areas, suggesting that suppression of the anthocyanin branch may result in re-routing phenylpropanoid flux into the CGA or lignin biosynthesis branches. Two R2R3 MYB TFs, StMYB44-1 and StMYB44-2, were highly expressed in white regions under high temperature. In transient assays, StMYB44 represses anthocyanin accumulation in leaves of Nicotiana tabacum and N. benthamiana by directly suppressing the activity of the dihydroflavonol reductase (DFR) promoter. StMYB44-1 showed stronger repressive capacity than StMYB44-2, with both predicted proteins containing the repression-associated EAR motif with some variation. StMYB44-1 conferred repression without a requirement for a basic helix-loop-helix (bHLH) partner, suggesting a different repression mechanism from that of reported anthocyanin repressors. We propose that temperature-induced reduction of anthocyanin accumulation in potato flesh is caused by down-regulation of the activating anthocyanin regulatory complex, by enhancing the expression of flesh-specific StMYB44 and alteration of phenylpropanoid flux.

Comparative Study on the Chemical Structure and In Vitro Antiproliferative Activity of Anthocyanins in Purple Root Tubers and Leaves of Sweet Potato ( Ipomoea batatas).

The structure and in vitro antiproliferative activity of anthocyanins in the root tubers of a sweet potato variety cv. Bhu Krishna and the purple leaves of a promising accession S-1467 were studied with the objectives of understanding the structure-activity relationship and comparing the leaf and tuber anthocyanins. The chemical structure of anthocyanins was determined by high-resolution electrospray ionization mass spectrometry analysis. A fluorescence-resonance-energy-transfer-based caspase sensor probe had been used to study the antiproliferative property, and analysis of the cell cycle was performed after staining with propidium iodide and subsequent fluorescence-activated cell sorting. Structurally, the anthocyanins in root tubers were identical to those in leaves, but there was a difference in the proportion of various aglycones present in both. This has led to distinguishable differences in the antiproliferative activity of leaf and tuber anthocyanins to various cancer cells. All nine anthocyanins were found in acylated forms in both tubers and leaves. However, peonidin derivatives were major anthocyanins in tubers (33.98 ± 1.41 mg) as well as leaves (27.68 ± 1.07 mg). The cyanidin derivatives were comparatively higher in leaves (20.55 ± 0.91 mg) than tubers (9.44 ± 0.94 mg). The tuber and leaf anthocyanins exhibited potential antiproliferative properties to MCF-7, HCT-116, and HeLa cancer cells, and the structure of anthocyanins had a critical role in it. The leaf anthocyanins exhibited significantly higher activity against colon and cervical cancer cells, whereas tuber anthocyanins had a slightly greater effect against breast cancer cells.

A Root-Preferential DFR-Like Gene Encoding Dihydrokaempferol Reductase Involved in Anthocyanin Biosynthesis of Purple-Fleshed Sweet Potato.

Purple-fleshed sweet potato is good for health due to rich anthocyanins in tubers. Although the anthocyanin biosynthetic pathway is well understood in up-ground organs of plants, the knowledge on anthocyanin biosynthesis in underground tubers is limited. In the present study, we isolated and functionally characterized a root-preferential gene encoding dihydrokaempferol reductase (IbDHKR) from purple-fleshed sweet potato. IbDHKR showed highly similarity with the reported dihydroflavonol reductases in other plant species at the sequence levels and the NADPH-binding motif and the substrate-binding domain were also found in IbDHKR. The tissue profile showed that IbDHKR was expressed in all the tested organs, but with much higher level in tuber roots. The expression level of IbDHKR was consistent with the anthocyanin content in sweet potato organs, suggesting that tuber roots were the main organs to synthesize anthocyanins. The recombinant 44 kD IbDHKR was purified and fed by three different dihydroflavonol substrates including dihydrokaempferol (DHK), dihydroquerctin, and dihydromyrecetin. The substrate feeding assay indicated that only DHK could be accepted as substrate by IbDHKR, which was reduced to leucopelargonidin confirmed by LC-MS. Finally, IbDHKR was overexpressed in transgenic tobacco. The IbDHKR-overexpression tobacco corolla was more highly pigmented and contained higher level of anthocyanins than the wild-type tobacco corolla. In summary, IbDHKR was a root-preferential gene involved in anthocyanin biosynthesis and its encoding protein, specifically catalyzing DHK reduction to yield leucopelargonidin, was a candidate gene for engineering anthocyanin biosynthetic pathway.

Influence of Biodynamic Preparations on the Quality Indices and Antioxidant Compounds Content in the Tubers of Coloured Potatoes (Solanum tuberosum L.)

Biodynamic preparations 500 and 501 are plant strengthening agents of biodynamic agriculture method, prepared of manure and powdered quartz. The objective of the present study was to determine effects of biodynamic (BD) preparations 500 and 501 on the quality indices and antioxidant compounds content in the tubers of coloured flesh potatoes. Theexperiment included two factors: potato cultivar and treatment with BD preparations as field sprays. The experiment was carried out in four replications, in a randomly design. Results showed that application of BD preparations did not influence significantly the contents of dry matter, crude fibre and crude ash in all tested cultivars. Separately used BD preparation 500 increased content of total anthocyanins in tubers of ‘Vitelotte’ and ‘Red Emmalie’ and leucoanthocyanins content in ‘BlueCongo’, but decreased the content of total phenolics in all cultivars. Treatment with BD preparation 501 had significant effect on the contents of total phenolics and total anthocyanins in all cultivars. However, treatment with BD preparation 500 in combination with BD preparation 501 substantially increased the contents of total phenolics and total anthocyanins in all cultivars. Tubers of ‘Vitelotte’ with dark-purple flesh contained significantly more antioxidant compounds than the lightpurpleand red.

Flavonoid profiling and transcriptome analysis reveals new gene-metabolite correlations in tubers of Solanum tuberosum L.

Anthocyanin content of potato tubers is a trait that is attracting increasing attention as the potential nutritional benefits of this class of compound become apparent. However, our understanding of potato tuber anthocyanin accumulation is not complete. The aim of this study was to use a potato microarray to investigate gene expression patterns associated with the accumulation of purple tuber anthocyanins. The advanced potato selections, CO97216-3P/PW and CO97227-2P/PW, developed by conventional breeding procedures, produced tubers with incomplete expression of tuber flesh pigmentation. This feature permits sampling pigmented and non-pigmented tissues from the same tubers, in essence, isolating the factors responsible for pigmentation from confounding genetic, environmental, and developmental effects. An examination of the transcriptome, coupled with metabolite data from purple pigmented sectors and from non-pigmented sectors of the same tuber, was undertaken to identify these genes whose expression correlated with elevated or altered polyphenol composition. Combined with a similar study using eight other conventional cultivars and advanced selections with different pigmentation, it was possible to produce a refined list of only 27 genes that were consistently differentially expressed in purple tuber tissues compared with white. Within this list are several new candidate genes that are likely to impact on tuber anthocyanin accumulation, including a gene encoding a novel single domain MYB transcription factor.