Effect of ABA upon anthocyanin synthesis in regenerated torenia shoots

Unveiling the protective role of anthocyanin in rice: insights into drought-induced oxidative stress and metabolic regulation

This study investigates the impact of anthocyanin treatment on rice plants under drought stress, focusing on phenotypic, molecular, and biochemical responses. Anthocyanin were treated to one month old plants one week before the droughtexposure. Drought stress was imposed by using 10% polyethylene glycol (PEG 6000). Anthocyanin-treated plants exhibited significant enhancements in various traits, including growth parameters and reproductive characteristics, under normal conditions. When subjected to drought stress, these plants displayed resilience, maintaining or improving essential morphological and physiological features compared to non-treated counterparts. Notably, anthocyanin application mitigated drought-induced oxidative stress, as evidenced by reduced levels of reactive oxygen species (ROS) and lipid membrane peroxidation. The study also elucidates the regulatory role of anthocyanins in the expression of flavonoid biosynthetic genes, leading to increased levels of key secondary metabolites. Furthermore, anthocyanin treatment influenced the levels of stress-related signaling molecules, including melatonin, proline, abscisic acid (ABA), and salicylic acid (SA), contributing to enhanced stress tolerance. The enzymatic activity of antioxidants and the expression of drought-responsive genes were modulated by anthocyanins, emphasizing their role in antioxidant defense and stress response. Additionally, anthocyanin treatment positively influenced macronutrient concentrations, particularly calcium ion (Ca+), potassium ion (K+), and sodium ion (Na+), essential for cell wall and membrane stability. The findings collectively highlight the multifaceted protective effects of anthocyanins, positioning them as potential key players in conferring resilience to drought stress in rice plants. The study provides valuable insights into the molecular and physiological mechanisms underlying anthocyanin-mediated enhancement of drought stress tolerance, suggesting promising applications in agricultural practices for sustainable crop production.

A novel ABA-insensitive mutant in Arabidopsis reveals molecular network of ABA-induced anthocyanin accumulation and abiotic stress tolerance

Abscisic acid (ABA) plays primary regulatory roles in abiotic stress tolerance and seed germination. Here, we report a unique novel Arabidopsis abscisic acid-insensitive mutant, abr (abscisic acid resistance), which was able to germinate in medium containing high ABA concentrations and tolerant to abiotic stress tolerance. We observed that abr mutant accumulated more anthocyanins by ABA treatment than did the wild type (WT). Dimethylthiourea (DMTU, an H₂O₂ scavenger) was effective in inhibiting ABA-induced anthocyanins accumulation. RNA-seq showed that the expression of anthocyanins synthesis, antioxidant enzyme and stress-related genes were specifically increased in ABA-treated abr seedlings, suggesting that the abr mutation affects stress response as well as ABA responses. Interestingly, seedlings accumulating anthocyanins exhibited more tolerance to mannitol and NaCl compared to wild type. We propose that ABA-induced H₂O₂ generation triggers the foliar anthocyanins accumulation, which, in turn, enhances the abiotic stress tolerance in abr mutant.

Structure, synthesis, biosynthesis, and activity of the characteristic compounds from Ginkgo biloba L

Covering: 1928-2021Ginkgo biloba L. is one of the most distinctive plants to have emerged on earth and has no close living relatives. Owing to its phylogenetic divergence from other plants, G. biloba contains many compounds with unique structures that have served to broaden the chemical diversity of herbal medicine. Examples of such compounds include terpene trilactones (ginkgolides), acylated flavonol glycosides (ginkgoghrelins), biflavones (ginkgetin), ginkgotides and ginkgolic acids. The extract of G. biloba leaf is used to prevent and/or treat cardiovascular diseases, while many ginkgo-derived compounds are currently at various stages of preclinical and clinical trials worldwide. The global annual sales of G. biloba products are estimated to total US$10 billion. However, the content and purity of the active compounds isolated by traditional methods are usually low and subject to varying environmental factors, making it difficult to meet the huge demand of the international market. This highlights the need to develop new strategies for the preparation of these characteristic compounds from G. biloba. In this review, we provide a detailed description of the structures and bioactivities of these compounds and summarize the recent research on the development of strategies for the synthesis, biosynthesis, and biotechnological production of the characteristic terpenoids, flavonoids, and alkylphenols/alkylphenolic acids of G. biloba. Our aim is to provide an important point of reference for all scientists who research ginkgo-related compounds for medicinal or other purposes.

Sucrose Enhances Anthocyanin Accumulation in Torenia by Promoting Expression of Anthocyanin Biosynthesis Genes

We examined the effects of different sucrose concentrations (3%, 5%, and 7%) on anthocyanin accumulation and plant growth in wild type (WT) and transgenic (T2) torenia cultivar “Kauai Rose” overexpressing the anthocyanin regulatory transcription factors B-Peru + mPAP1 or RsMYB1. Sucrose increased anthocyanin production in both WT and transgenic plants, with higher anthocyanin production in transgenic plants compared to WT plants. Higher sucrose concentrations increased production of anthocyanin in transgenic and WT plants, with increased anthocyanin production associated with increased expression of anthocyanin biosynthesis genes. Higher sucrose concentrations reduced growth of WT and transgenic plants. Our results indicate that sucrose enhances anthocyanin production in torenia by regulating anthocyanin biosynthesis genes.

Repressors of anthocyanin biosynthesis

Anthocyanins play a variety of adaptive roles in both vegetative tissues and reproductive organs of plants. The broad functionality of these compounds requires sophisticated regulation of the anthocyanin biosynthesis pathway to allow proper localization, timing, and optimal intensity of pigment deposition. While it is well-established that the committed steps of anthocyanin biosynthesis are activated by a highly conserved MYB-bHLH-WDR (MBW) protein complex in virtually all flowering plants, anthocyanin repression seems to be achieved by a wide variety of protein and small RNA families that function in different tissue types and in response to different developmental, environmental, and hormonal cues. In this review, we survey recent progress in the identification of anthocyanin repressors and the characterization of their molecular mechanisms. We find that these seemingly very different repression modules act through a remarkably similar logic, the so-called 'double-negative logic'. Much of the double-negative regulation of anthocyanin production involves signal-induced degradation or sequestration of the repressors from the MBW protein complex. We discuss the functional and evolutionary advantages of this logic design compared with simple or sequential positive regulation. These advantages provide a plausible explanation as to why plants have evolved so many anthocyanin repressors.

The transcription factor AtGLK1 acts upstream of MYBL2 to genetically regulate sucrose-induced anthocyanin biosynthesis in Arabidopsis

BACKGROUND

The regulation of anthocyanin biosynthesis by various factors including sugars, light and abiotic stresses is mediated by numerous regulatory factors acting at the transcriptional level. Here experimental evidence was provided in order to demonstrate that the nuclear GARP transcription factor AtGLK1 plays an important role in regulating sucrose-induced anthocyanin biosynthesis in Arabidopsis.

RESULTS

The results obtained using real-time quantitative PCR and GUS staining assays revealed that AtGLK1 was mainly expressed in the green tissues of Arabidopsis seedlings and could be induced by sucrose. The loss-of-function glk1 glk2 double mutant has lower anthocyanin levels than the glk2 single mutant, although it has been determined that loss of AtGLK1 alone does not affect anthocyanin accumulation. Overexpression of AtGLK1 enhances the accumulation of anthocyanin in transgenic Arabidopsis seedlings accompanied by increased expression of anthocyanin biosynthetic and regulatory genes. Moreover, we found that AtGLK1 also participates in plastid-signaling mediated anthocyanin accumulations. Genetic, physiological, and molecular biological approaches demonstrated that AtGLK1 acts upstream of MYBL2, which is a key negative regulator of anthocyanin biosynthesis, to genetically regulate sucrose-induced anthocyanin biosynthesis.

CONCLUSION

Our results indicated that AtGLK1 positively regulates sucrose-induced anthocyanin biosynthesis in Arabidopsis via MYBL2.

The Purple Leaf (pl6) Mutation Regulates Leaf Color by Altering the Anthocyanin and Chlorophyll Contents in Rice

The anthocyanin biosynthesis attracts strong interest due to the potential antioxidant value and as an important morphological marker. However, the underlying mechanism of anthocyanin accumulation in plant tissues is not clearly understood. Here, a rice mutant with a purple color in the leaf blade, named pl6, was developed from wild type (WT), Zhenong 41, with gamma ray treatment. By map-based cloning, the OsPL6 gene was located on the short arm of chromosome 6. The multiple mutations, such as single nucleotide polymorphism (SNP) at −702, −598, −450, an insertion at −119 in the promoter, three SNPs and one 6-bp deletion in the 5′-UTR region, were identified, which could upregulate the expression of OsPL6 to accumulate anthocyanin. Subsequently, the transcript level of structural genes in the anthocyanin biosynthesis pathway, including OsCHS, OsPAL, OsF3H and OsF3′H, was elevated significantly. Histological analysis revealed that the light attenuation feature of anthocyanin has degraded the grana and stroma thylakoids, which resulted in poor photosynthetic efficiency of purple leaves. Despite this, the photoabatement and antioxidative activity of anthocyanin have better equipped the pl6 mutant to minimize the oxidative damage. Moreover, the contents of abscisic acid (ABA) and cytokanin (CK) were elevated along with anthocyanin accumulation in the pl6 mutant. In conclusion, our results demonstrate that activation of OsPL6 could be responsible for the purple coloration in leaves by accumulating excessive anthocyanin and further reveal that anthocyanin acts as a strong antioxidant to scavenge reactive oxygen species (ROS) and thus play an important role in tissue maintenance.

Exposure to endophytic fungi quantitatively and compositionally alters anthocyanins in grape cells

Anthocyanins contribute greatly to the organoleptic and biochemical properties of grapes and wines. Although there are broadly documented factors involved in grape anthocyanin synthesis, the present work focused on fungal endophytes and their possible role in grape coloration. Our results showed that exposure to endophytic fungi within a dual culture system differentially affected total anthocyanin concentrations and PAL activities in grape cells. Grape cells dual cultured with fungal strains XH-2, R2-21 and B2-17 showed significant differences of their anthocyanin concentrations were subjected to further analysis of their anthocyanidin compositions. Compared to the no-fungus controls, grape cells exposed to fungal strains XH-2 and R2-21 exhibited quantitative promotion of their total anthocyanidin concentrations by 74% and 28%, respectively, whereas treatment with the fungus B2-17 reduced the anthocyanidin content by 19%. A total of 14 species of anthocyanidins were detected from the grape cells in these experiments. Most interestingly, exposure to any of these fungal strains differentially modified the compositional patterns of grape cellular anthocyanidins. The obvious upregulation of the transcription of VvMYB in grape cells treated with fungal strains XH-2 and R2-21 implies that the increased anthocyanin levels in these grape cells may be due to the activated transcriptional factors. In addition, the exposure of grape cells to extracts of these fungi initiated similar responses of anthocyanin contents and PAL activities to exposure to the living fungi and appeared obvious dosage effects. The influence of fungal endophytes on the coloration of grape berries was also examined in this study.

Abscisic acid is involved in phenolic compounds biosynthesis, mainly anthocyanins, in leaves of Aristotelia chilensis plants (Mol.) subjected to drought stress

Abscisic acid (ABA) regulates the physiological and biochemical mechanisms required to tolerate drought stress, which is considered as an important abiotic stress. It has been postulated that ABA might be involved in regulation of plant phenolic compounds biosynthesis, especially anthocyanins that accumulate in plants subjected to drought stress; however, the evidence for this postulate remains elusive. Therefore, we studied whether ABA is involved in phenolic compounds accumulation, especially anthocyanin biosynthesis, using drought stressed Aristotelia chilensis plants, an endemic berry in Chile. Our approach was to use fluridone, an ABA biosynthesis inhibitor, and then subsequent ABA applications to young and fully-expanded leaves of drought stressed A. chilensis plants during 24, 48 and 72 h of the experiment. Plants were harvested and leaves were collected separately to determine the biochemical status. We observed that fluridone treatments significantly decreased ABA concentrations and total anthocyanin (TA) concentrations in stressed plants, including both young and fully-expanded leaves. TA concentrations following fluridone treatment were reduced around fivefold, reaching control plant levels. ABA application restored ABA levels as well as TA concentrations in stressed plant at 48 h of the experiment. We also observed that TA concentrations followed the same pattern as ABA concentrations in the ABA treated plants. Quantitative real-time PCR revealed that AcUFGT gene expression decreased in fully-expanded leaves of stressed plants treated with fluridone, while a subsequent ABA application increased AcUFGT expression. Taken together, our results suggest that ABA is involved in the regulation of anthocyanin biosynthesis under drought stress.

Evaluating the involvement and interaction of abscisic acid and miRNA156 in the induction of anthocyanin biosynthesis in drought-stressed plants

ABA is involved in anthocyanin synthesis through the regulation of microRNA156, augmenting the level of expression of anthocyanin synthesis-related genes and, therefore, increasing anthocyanin level. Drought stress is the main cause of agricultural crop loss in the world. However, plants have developed mechanisms that allow them to tolerate drought stress conditions. At cellular level, drought stress induces changes in metabolite accumulation, including increases in anthocyanin levels due to upregulation of the anthocyanin biosynthetic pathway. Recent studies suggest that the higher anthocyanin content observed under drought stress conditions could be a consequence of a rise in the abscisic acid (ABA) concentration. This plant hormone crosses the plasma membrane by specific transporters, and it is recognized at the cytosolic level by receptors known as pyrabactin resistance (PYR)/regulatory component of ABA receptors (PYR/RCARs) that regulate downstream components. In this review, we discuss the hypothesis regarding the involvement of ABA in the regulation of microRNA156 (miRNA156), which is upregulated as part of dehydration stress responsiveness in different species. The miRNA156 upregulation produces a greater level of anthocyanin gene expression, forming the multienzyme complex that will synthesize an increased level of anthocyanins at the cytosolic face of the rough endoplasmic reticulum (RER). After synthesis, anthocyanins are transported from the RER to the vacuole by two possible models of transport: (1) membrane vesicle-mediated transport, or (2) membrane transporter-mediated transport. Thus, the aim was to analyze the recent findings on synthesis, transport and the possible mechanism by which ABA could increase anthocyanin synthesis under drought stress conditions potentially throughout microRNA156 (miRNA156).

Identification of anthocyanin biosynthesis related microRNAs in a distinctive Chinese radish (Raphanus sativus L.) by high-throughput sequencing

Anthocyanins are widely distributed water-soluble phytochemical pigments belonging to the flavonoid group. To date, limited knowledge is available about the regulatory roles of miRNAs in anthocyanin biosynthesis in plants. To identify the miRNAs associated with anthocyanin biosynthesis in radish, five small RNA (sRNA) libraries constructed from 'Xinlimei' radish roots at 11, 21, 44, 56 and 73 days (d) were examined using high-throughput sequencing technology. A total of 102.02 million (M) clean reads were generated, from which 483 known and 1415 novel miRNAs were identified. Combined with target prediction and annotation, 72 differentially expressed miRNAs (52 known and 20 novel miRNAs) were more likely to participate in anthocyanin biosynthesis. Several target genes for these miRNAs encode a few transcription factors, including Myb domain (MYB), basic helix-loop-helix (bHLH), WD40 repeat, squamosa promoter binding protein like (SPL), auxin response factor (ARF), ethylene insensitive 3 (EIN3), WRKY and MADS-box proteins. Furthermore, the expression patterns of some anthocyanin biosynthesis related miRNAs and their corresponding targets were validated by RT-qPCR. Based on the characterization of anthocyanin biosynthesis related miRNAs and their target genes, a putative miRNA-target module regulating anthocyanin biosynthesis was proposed. This study represents the first genome-wide identification of miRNAs associated with anthocyanin biosynthesis in radish, and provides insights into the molecular mechanisms underlying regulation of anthocyanin biosynthesis in radish and other crops.

Short-day signals are crucial for the induction of anthocyanin biosynthesis in Begonia semperflorens under low temperature condition

The leaves of Begonia semperflorens accumulate anthocyanins and turn red in autumn in sub-temperate areas. This induction of anthocyanin biosynthesis in autumn has been attributed to the effects of low temperature, but the effects of different light regimes on this process are still being debated. In the present work, short days were found to be necessary for anthocyanin biosynthesis at low temperature. Under the same low-temperature conditions, Begonia seedlings grown under the short-day condition accumulated more carbohydrates and abscisic acid (ABA), which both induce anthocyanin biosynthesis. However, fewer carbohydrates and more gibberellin (GA) accumulated under the long-day conditions to maintain growth, which blocked anthocyanin biosynthesis and resulted in a lack of increases in the activities of dihydroflavonol 4-reductase (DFR) and flavonoid-3-O-glucosyl transferase (UFGT). Consequently, carbon flux, which was altered due to the blockade of anthocyanin synthesis, was channelled into the production of quercetin and phenolic acids but not lignin.

Transcriptomic Analysis Reveals Possible Influences of ABA on Secondary Metabolism of Pigments, Flavonoids and Antioxidants in Tomato Fruit during Ripening

Abscisic acid (ABA) has been proven to be involved in the regulation of climacteric fruit ripening, but a comprehensive investigation of its influence on ripening related processes is still lacking. By applying the next generation sequencing technology, we conducted a comparative analysis of the effects of exogenous ABA and NDGA (Nordihydroguaiaretic acid, an inhibitor of ABA biosynthesis) on tomato fruit ripening. The high throughput sequencing results showed that out of the 25728 genes expressed across all three samples, 10388 were identified as significantly differently expressed genes. Exogenous ABA was found to enhance the transcription of genes involved in pigments metabolism, including carotenoids biosynthesis and chlorophyll degradation, whereas NDGA treatment inhibited these processes. The results also revealed the crucial role of ABA in flavonoids synthesis and regulation of antioxidant system. Intriguingly, we also found that an inhibition of endogenous ABA significantly enhanced the transcriptional abundance of genes involved in photosynthesis. Our results highlighted the significance of ABA in regulating tomato ripening, which provided insight into the regulatory mechanism of fruit maturation and senescence process.

The Arabidopsis thaliana RNA-binding protein FCA regulates thermotolerance by modulating the detoxification of reactive oxygen species

Heat stress affects various aspects of plant growth and development by generating reactive oxygen species (ROS) which cause oxidative damage to cellular components. However, the mechanisms by which plants cope with ROS accumulation during their thermotolerance response remain largely unknown. Here, we demonstrate that the RNA-binding protein FCA, a key component of flowering pathways in Arabidopsis thaliana, is required for the acquisition of thermotolerance. Transgenic plants overexpressing the FCA gene (35S:FCA) were resistant to heat stress; the FCA-defective fca-9 mutant was sensitive to heat stress, consistent with induction of the FCA gene by heat. Furthermore, total antioxidant capacity was higher in the 35S:FCA transgenic plants but lower in the fca-9 mutant compared with wild-type controls. FCA interacts with the ABA-INSENSITIVE 5 (ABI5) transcription factor, which regulates the expression of genes encoding antioxidants, including 1-CYSTEINE PEROXIREDOXIN 1 (PER1). We found that FCA is needed for proper expression of the PER1 gene by ABI5. Our observations indicate that FCA plays a role in the induction of thermotolerance by triggering antioxidant accumulation under heat stress conditions, thus providing a novel role for FCA in heat stress responses in plants.

A novel role for Arabidopsis CBL1 in affecting plant responses to glucose and gibberellin during germination and seedling development

Glucose and phytohormones such as abscisic acid (ABA), ethylene, and gibberellin (GA) coordinately regulate germination and seedling development. However, there is still inadequate evidence to link their molecular roles in affecting plant responses. Calcium acts as a second messenger in a diverse range of signal transduction pathways. As calcium sensors unique to plants, calcineurin B-like (CBL) proteins are well known to modulate abiotic stress responses. In this study, it was found that CBL1 was induced by glucose in Arabidopsis. Loss-of-function mutant cbl1 exhibited hypersensitivity to glucose and paclobutrazol, a GA biosynthetic inhibitor. Several sugar-responsive and GA biosynthetic gene expressions were altered in the cbl1 mutant. CBL1 protein physically interacted with AKINβ1, the regulatory β subunit of the SnRK1 complex which has a central role in sugar signaling. Our results indicate a novel role for CBL1 in modulating responses to glucose and GA signals.

Protective effect of extracts of Perilla frutescens treated with sucrose on tert-butyl hydroperoxide-induced oxidative hepatotoxicity in vitro and in vivo

Perilla frutescens leaves are often used in East Asian gourmet food. In this study, we investigated the hepatoprotective effects of P. frutescens leaves grown in different concentrations of sucrose (0, 115, 175 and 235 mM sucrose) leading to four samples of perilla leaf extracts (PLEs). Based on caffeic acid level and antioxidant activities, further experiments were conducted using perilla leaf extracts treated with 6% sucrose compared with non-treated perilla leaf extracts as a control. Oral intubation with non-treated perilla leaf extracts or perilla leaf extracts treated with 6% sucrose (1000 mg/kg b.w. rat) for 5 days was conducted before treatment with a single dose of tert-butyl hydroperoxide (0.5 mmol/kg b.w., i.p.) led to a significant reduction of hepatic toxicity in the perilla leaf extracts treated with 6% sucrose. We demonstrated that P. frutescens with higher contents of caffeic acid was produced, and that sucrose could play a role in the induction of this secondary metabolite. Sucrose-treated perilla leaves, which had better antioxidant activities than untreated leaves, can be used as a potential dietary source.

The ethylene signaling pathway has a negative impact on sucrose-induced anthocyanin accumulation in Arabidopsis

In an attempt to understand the complex regulatory mechanisms underlying sucrose-induced flavonoid biosynthesis, we examined several Arabidopsis mutants with altered anthocyanin accumulation. We determined that disruption of ethylene signaling results in a dramatic increase in sucrose-induced anthocyanin accumulation. Furthermore, we investigated why the ein2-1 (ethylene insensitive) Arabidopsis mutant accumulates higher levels of anthocyanin in response to sucrose than wild-type Arabidopsis. An increased level of PAP1 transcript in the ein2-1 mutant appears to be the main factor responsible for the increased accumulation of anthocyanin in response to sucrose. Therefore, our results indicate that the ethylene signaling pathway plays a negative role in sucrose-induced anthocyanin accumulation. We believe that the explanation for this observation may be related to the initiation of the senescence program in plants.

Variation and correlation analysis of flavonoids and carotenoids in Korean pigmented rice (Oryza sativa L.) cultivars

Flavonoids and carotenoids of pigmented rice ( Oryza sativa L.), including five black cultivars and two red cultivars, from Korea were characterized to determine the diversity among the phytochemicals and to analyze the relationships among their contents. Black cultivars were higher in flavonoids and carotenoids than the red and white cultivars. The profiles of eight phytochemicals identified from the rice grains were subjected to principal component analysis (PCA) to evaluate the differences among cultivars. PCA could fully distinguish between these cultivars. The Heugjinjubyeo (BR-1) and Heugseolbyeo (BR-2) cultivars were separated from the others based on flavonoid and carotenoid concentrations. Flavonoid contents had a positive correlation with carotenoid contents among all rice grains. The BR-1 and BR-2 cultivars appear to be good candidates for future breeding programs because they have simultaneously high flavonoid and carotenoid contents.

Fungal endophytes-induced abscisic acid is required for flavonoid accumulation in suspension cells of Ginkgo biloba

Treatment of suspension cells of Ginkgo biloba with fungal endophytes resulted in accumulation of flavonoids, increased abscisic acid (ABA) production and activation of phenylalanine ammonia-lyase (PAL). Fluridone, an inhibitor of ABA biosynthesis, was effective in inhibiting fungal endophytes-induced ABA biosynthesis, increase of PAL activity and flavonoids accumulation. Moreover, exogenous application of ABA enhanced PAL activity and increased accumulation of flavonoids in G. biloba cells with or without fungal endophytes elicitor. These finding suggest a causal relationship between ABA release and both PAL activity and flavonoid accumulation under fungal endophytes treatment and that ABA is involved in fungal endophytes-induced flavonoids accumulation in this plant.

Abscisic acid-induced hydrogen peroxide is required for anthocyanin accumulation in leaves of rice seedlings

The role of hydrogen peroxide (H(2)O(2)) in abscisic acid (ABA)-induced anthocyanin accumulation in detached and intact leaves of rice seedlings was investigated. Treatment with ABA resulted in an accumulation of anthocyanins in detached rice leaves. Dimethylthiourea, a chemical trap for H(2)O(2), was observed to be effective in inhibiting ABA-induced accumulation of anthocyanins. Inhibitors of NADPH oxidase (diphenyleneiodonium chloride and imidazole), phosphatidylinositol 3-kinase (wortmannin and LY 294002), and a donor of nitric oxide (N-tert-butyl-alpha-phenylnitrone), which have previously been shown to prevent ABA-induced H(2)O(2) accumulation in detached rice leaves, inhibited ABA-induced anthocyanin increase. Exogenous application of H(2)O(2), however, was found to increase the anthocyanin content of detached rice leaves. In terms of H(2)O(2) accumulation, intact (attached) leaves of rice seedlings of cultivar Taichung Native 1 (TN1) are ABA sensitive and those of cultivar Tainung 67 (TNG67) are ABA insensitive. Upon treatment with ABA, H(2)O(2) and anthocyanins accumulated in leaves of TN1 seedlings but not in leaves of TNG67. Our results, obtained from detached and intact leaves of rice seedlings, suggest that H(2)O(2) is involved in ABA-induced anthocyanin accumulation in this species.