Expression Of Carotenoid Biosynthetic Genes Research Articles

Water saving irrigation mediates bioactive pigments metabolism and storage capacity in tomato fruit

Tomato fruit consumption is influenced by flavor and nutrient quality. In the present study, we investigate the impact of water saving irrigation (WSI) as a pre-harvest management on flavor and nutrient quality of tomato fruit. Our results demonstrate that WSI-treated tomato fruit exhibited improved sensory scores as assessed by a taste panel, accompanied by elevated levels of SlGLK2 expression, sugars, acids, and carotenoid contents compared to non-treated fruit. Notably, WSI treatment significantly enhanced the development of chloroplast and plastoglobulus in chromoplast, which served as carotenoid storage sites and upregulated the expression of carotenoid biosynthetic genes. Furthermore, integrated transcriptome and metabolome analysis revealed heightened expression of sugar and flavonoid metabolism pathways in WSI-treated tomato fruit. Remarkably, the master regulator SlMYB12 displayed a substantially increased expression due to WSI. These findings suggest that WSI is an effective and sustainable approach to enhance the pigments metabolism and storage capacity as well as the organoleptic characteristics and nutritional value of tomato fruit, offering a win-win solution for both water conservation and quality improvement in agro-food production.

Characterization of granulation in citrus “Harumi” fruit during postharvest storage

Granulation is a serious physiological disorder in citrus fruit, which impairs the fruit quality and causes economic losses to the citrus industry. ‘Harumi’ ((Citrus unshiu × C. sinensis) × C. reticulate), a mandarin-type variety, is prone to granulation, especially after long-term storage. In the present study, to elucidate the molecular mechanism of granulation, physiochemical changes were investigated in the juice sacs of ‘Harumi’ during the granulation process. The results showed that large size fruit (L fruit, transverse diameter of 8.5 - 10.0 cm) was prone to granulation, while small size fruit (S fruit, transverse diameter of 5.0 - 6.5 cm) was not. In L fruit, lignin content increased rapidly, which was accompanied by the reduction of the content of sugars (fructose and glucose) and organic acid (citric acid) during the granulation process. Moreover, the occurrence of granulation inhibited carotenoid biosynthesis in the ‘Harumi’ fruit. In L fruit, the content of the major carotenoids, β-cryptoxanthin, all-trans-violaxanthin, and 9-cis-violaxanthin, were decreased during the granulation process, and as a result, total carotenoid content in L fruit was 75.8% lower than that in S fruit in the fifth month after harvest. The real-time PCR results showed that the expression of carotenoid biosynthetic genes (CitPSY, CitPDS, CitZDS, CitLCYb2, and CitHYb) was down-regulated, while the expression of carotenoid catabolic genes (CitNCED2 and CitNCED3) was up-regulated in L fruit during the granulation process. This study is the first to investigate the carotenoid metabolism during the granulation process, which will provide new insights into exploring the causes of granulation in citrus fruit.

β-Carotene and lutein accumulation, and carotenoid biosynthetic gene expression during fruit development and fruit ripening of A genome banana

• β -carotene and lutein content, affecting to orange-yellow pulp color in KK2. • Expression of MaPSY2a gene in KK2 affected to carotenoids accumulation. • Carotenoid biosynthetic genes correlated with β -carotene and lutein level. • Difference of A genome composition in banana affects carotenoid accumulation. Bananas ( Musa spp.) are an important source of pro-vitamin A, derived from carotenoids. Some cultivated bananas originated from intra-specific hybridization resulting in genotypes which are diploid (AA) and triploid (AAA) genomes that are the most important bananas for desserts. The accumulation of carotenoids and transcripts of genes related to carotenoid biosynthesis during fruit development and ripening in cultivars carrying the banana A genome (AA and AAA) were investigated. The accumulation of total carotenoids was greatest in ‘Khai Kasetsart2’ (KK2; AA) and ‘Sa’ (SA; AA), and comparatively lower in other cultivars. The predominant carotenoids in this fruit were β- carotene and lutein, with a small amount of α- carotene, which correlate with the orange-yellow pulp color (in particular KK2). In contrast, Leb Mu Nang had the lowest total carotenoids during fruit development while lutein and β -carotene in Hom Thong increased with fruit ripening. MaPSY2a gene expression in KK2 and SA cultivars occurred throughout fruit development but declined during fruit ripening. The expression of MaLCYB, MaLCYE, MaCHYB , and MaCHYE genes increased throughout fruit development and during fruit ripening resulting in β- carotene and lutein high content. In cultivars with low carotenoid levels, MaLCYB gene expression was reduced, while the MaLCYE, MaCHYE, and MaCHYB genes were up-regulated during fruit ripening. Besides, the MaCCD4 gene (a gene associated with carotenoid turnover) had lower expression throughout fruit development and ripening in KK2 compared to the other cultivars. These results suggested that the different carotenoid accumulation patterns in the cultivars could be attributed to differential gene expression and A genome composition.

G2-LIKE CAROTENOID REGULATOR (SlGCR) is a positive regulator of lutein biosynthesis in tomato

Lutein is an oxygen-containing carotenoid synthesized in plant chloroplasts and chromoplasts. It plays an indispensable role in promoting plant growth and maintaining eye health in humans. The rate-limiting step of lutein biosynthesis is catalyzed by the lycopene ε-cyclase enzyme (LCYE). Although great progress has been made in the identification of transcription factors involved in the lutein biosynthetic pathway, many systematic molecular mechanisms remain to be elucidated. Here, using co-expression analysis, we identified a gene, G2-LIKE CAROTENOID REGULATOR (SlGCR), encoding a GARP G2-like transcription factor, as the potential regulator of SlLCYE in tomato. Silencing of SlGCR reduced the expression of carotenoid biosynthetic genes and the accumulation of carotenoids in tomato leaves. By contrast, overexpression of SlGCR in tomato fruit significantly increased the expression of relevant genes and enhanced the accumulation of carotenoids. SlGCR can directly bind to the SlLCYE promoter and activate its expression. In addition, we also discovered that expression of SlGCR was negatively regulated by the master regulator SlRIN, thereby inhibiting lutein synthesis during tomato fruit ripening. Taken together, we identified SlGCR as a novel regulator involved in tomato lutein biosynthesis, elucidated the regulatory mechanism, and provided a potential tool for tomato lutein metabolic engineering.

Carotenoid biosynthetic gene expression, pigment and n-3 fatty acid contents in carotenoid-rich Tetraselmis striata CTP4 strains under heat stress combined with high light

In this study, two carotenoid-rich strains of the euryhaline microalga Tetraselmis striata CTP4 were isolated by random mutagenesis combined with selection via fluorescence activated cell sorting and growth on norflurazon. Both strains, ED5 and B11, showed an up to 1.5-fold increase in carotenoid contents as compared with the wildtype, independent of the growth conditions. More specifically, violaxanthin, β-carotene and lutein contents reached as high as 1.63, 4.20 and 3.81 mg g−1 DW, respectively. Genes coding for phytoene synthase, phytoene desaturase, lycopene-β-cyclase and ε-ring hydroxylase involved in carotenoid biosynthesis were found to be upregulated in ED5 and B11 cells as compared to the wildtype. Both strains showed higher contents of eicosapentaenoic acid as compared with those of the wildtype, reaching up to 4.41 and 2.88 mg g−1 DW, respectively. Overall, these results highlight the complexity of changes in carotenoid biosynthesis regulation that are required to improve pigment contents in microalgae.

Carotenoid Accumulation and the Expression of Carotenoid Metabolic Genes in Mango during Fruit Development and Ripening

Carotenoids are considered to be important components in mango fruits. However, there is a lack of understanding about the regulation of carotenoids in mango. To gain an insight into the carotenoid metabolism pathway, carotenoid content and the expression of carotenoid metabolic genes were investigated in the peel and pulp of mango during fruit development and ripening in three cultivars, ‘Kaituk’, ‘Nam Dok Mai No.4′, and ‘Nam Dok Mai Sithong’, which are different in color. The highest carotenoid content was observed in ‘Kaituk’, followed by ‘Nam Dok Mai No.4′ and ‘Nam Dok Mai Sithong’, with the major carotenoid being β-carotene. The gene expression analysis found that carotenoid metabolism in mango fruit was primarily regulated at the transcriptional level. The changing patterns of carotenoid biosynthetic gene expression (MiPSY, MiPDS, MiZDS, MiCRTISO, MiLCYb, MiLCYe, MiHYb, and MiZEP) were similar to carotenoid accumulation, and ‘Kaituk’ exhibited a higher expression level than the other two cultivars. In addition, the differential regulation of carotenoid catabolic genes was found to be a mechanism responsible for variability in carotenoid content among the three mango cultivars. The expression of carotenoid catabolic genes (MiCCD1, MiNCED2, and MiNCED3) more rapidly decreased in ‘Kaituk’, resulting in a larger amount of carotenoids in ‘Kaituk’ than the other two cultivars.

LED-Induced Carotenoid Synthesis and Related Gene Expression in Brassica Microgreens

In this study, various ratios of combined red, blue, and amber light-emitting diodes (rbaLEDs) were investigated for their effect on the expression of carotenoid biosynthetic genes and carotenoid accumulation in eight Brassica microgreens. Total and individual (β-carotene, lutein, α-carotene, neoxanthin, and violaxanthin) carotenoids were increased 20-44 and 10-55%, respectively, under dose-dependent increasing amber-blue light and decreasing red in most microgreens. Lipophilic 2,2-diphenyl-1-picrylhydrazyl and ferric reducing antioxidant power antioxidant activities were significantly increased under higher amber and blue light fractions, while oxygen radical absorbance capacity was generally decreased. Under rbaLED in mizuna (B. rapa) microgreens, the lycopene epsilon cyclase (LYCε) expression was 10-15-fold higher, which resulted in downstream accumulation of α-carotene and lutein. Lycopene beta cyclase (LYCβ) was not significantly changed, suggesting that β-carotene, violaxanthin and neoxanthin were mainly controlled by upstream phytoene synthase and branch-point LYCε. Increased beta-ring carotenoid hydroxylase (CHXβ) expression was also consistent with lutein accumulation. This study demonstrated for the first time that amber LED was involved in the regulatory mechanism of carotenoid biosynthesis, thus a potential novel approach to production of antioxidant-rich microgreens.

Regulation of fruit ripening by the brassinosteroid biosynthetic gene SlCYP90B3 via an ethylene-dependent pathway in tomato

The essential role of ethylene in fruit ripening has been thoroughly studied. However, the involvement of brassinosteroids (BRs) in the regulation of fruit ripening and their relationship with the ethylene pathway are poorly understood. In the current study, we found that BRs were actively synthesized during tomato fruit ripening. We then generated transgenic lines overexpressing or silencing SlCYP90B3, which encodes a cytochrome P450 monooxygenase that catalyzes the rate-limiting step of BR synthesis. The expression level of SlCYP90B3 was positively related to the contents of bioactive BRs as well as the ripening process in tomato fruit, including enhanced softening and increased soluble sugar and flavor volatile contents. Both carotenoid accumulation and ethylene production were strongly correlated with the expression level of SlCYP90B3, corroborated by the altered expression of carotenoid biosynthetic genes as well as ethylene pathway genes in transgenic tomato fruits. However, the application of the ethylene perception inhibitor 1-methycyclopropene (1-MCP) abolished the promotion effect of SlCYP90B3 overexpression on carotenoid accumulation. Taken together, these results increase our understanding of the involvement of SlCYP90B3 in bioactive BR biosynthesis as well as fruit ripening in tomato, thus making SlCYP90B3 a target gene for improvement of visual, nutritional and flavor qualities of tomato fruits with no yield penalty.

Accumulation characteristics of carotenoids and adaptive fruit color variation in ornamental pepper

To understand better the mechanisms of the pigment accumulation in ornamental pepper, the fruit color, pigment and expression of carotenoid biosynthetic genes were investigated. The test materials were divided into three categories. The first category included cultivars B3, J1, J2 and Q3, the second were M3, M3′, W8 and WU, C2, S1, W3 and W4 belonged to the third category. The pigment changes during ripening were characterized by loss of chlorophyll and anthocyanin, and a rapid accumulation of carotenoids. It was found that GGPS, PSY, CRTZ-2 and CCS genes have abundant transcription during the accumulation of carotenoids in ornamental pepper, which have a more important regulatory function. Correlation analysis were conducted between fruit color, pigment and expression of genes, it showed that there were significant correlation between key genes of carotenoid biosynthetic pathway, among which PSY was highly correlated with CCS and CRTZ-2, CCS was highly correlated with CRTZ-2. Chromaticity values were negatively correlated with anthocyanin content in fruits, and the correlation between a* and carotenoid content was significantly higher. The information will be benefit for exploring the carotenoid regulation mechanism of ornamental pepper, and providing theoretical for fruit color breeding of ornamental pepper.

Melatonin promotes carotenoid biosynthesis in an ethylene-dependent manner in tomato fruits

In tomato, red color is a key commercial trait and arises from the accumulation of carotenoids. Previous studies have revealed that melatonin promotes lycopene accumulation and ethylene production. However, it is unclear if melatonin similarly increases other carotenoids, and whether any increase of carotenoids in tomato fruit is directly related to ethylene production. In this study, changes in carotenoid profiles during fruit ripening were investigated in control (CK) and in fruits treated with melatonin (M50). The α, β-carotene, and lycopene levels were significantly increased in M50, and there was increased carotenoid biosynthetic gene expression. We also observed up-regulated transcript levels of SlRIN, SlCNR, and SlNOR in M50 compared to CK. To better understand the regulation of carotenoid biosynthesis by melatonin and its potential response to endogenous ethylene, we tested an ethylene-insensitive mutant, Never ripe (Nr). Melatonin-treated Nr failed to accumulate more carotenoids compared to CK, although there was significantly changed ethylene production. Additionally, there was no general upregulation of expression of ripening-related genes in this mutant under melatonin treatment. These results suggest melatonin function might require ethylene to promote carotenoid synthesis in tomato.

The MYB Activator WHITE PETAL1 Associates with MtTT8 and MtWD40-1 to Regulate Carotenoid-Derived Flower Pigmentation in Medicago truncatula.

Carotenoids are a group of natural tetraterpenoid pigments with indispensable roles in the plant life cycle and the human diet. Although the carotenoid biosynthetic pathway has been well characterized, the regulatory mechanisms that control carotenoid metabolism, especially in floral organs, remain poorly understood. In this study, we identified an anthocyanin-related R2R3-MYB protein, WHITE PETAL1 (WP1), that plays a critical role in regulating floral carotenoid pigmentation in Medicago truncatula Carotenoid analyses showed that the yellow petals of the wild-type M. truncatula contained high concentrations of carotenoids that largely consisted of esterified lutein and that disruption of WP1 function via Tnt1 insertion led to substantially reduced lutein accumulation. WP1 mainly functions as a transcriptional activator and directly regulates the expression of carotenoid biosynthetic genes including MtLYCe and MtLYCb through its C-terminal acidic activation motif. Further molecular and genetic analyses revealed that WP1 physically interacts with MtTT8 and MtWD40-1 proteins and that this interaction facilitates WP1's function in the transcriptional activation of both carotenoid and anthocyanin biosynthetic genes. Our findings demonstrate the molecular mechanism of WP1-mediated regulation of floral carotenoid pigmentation and suggest that the conserved MYB-basic-helix-loop-helix-WD40 regulatory module functions in carotenoid biosynthesis in M. truncatula, with specificity imposed by the MYB partner.

Citrus tristeza virus-based induced gene silencing of phytoene desaturase is more efficient when antisense orientation is used

In this study, phytoene desaturase (PDS) in citrus and green fluorescent protein (GFP) in Nicotiana benthamiana (line 16c) were silenced by virus-induced gene silencing (VIGS) with Citrus tristeza virus (CTV), using the sense and antisense orientations. The antisense orientation showed a stronger reduction of GFP expression in N. benthamiana compared with the sense orientation. Similarly, the antisense orientation of pds induced stronger leaf photobleaching than the sense orientation. The antisense orientation produced higher levels of pds- and gfp-specific short interfering RNAs (siRNAs; ∼ 21 nucleotides) than the sense orientation. In addition, the antisense orientation of pds resulted in lower expression of carotenoid biosynthetic genes and produced lower levels of carotenoids and chlorophylls compared to the sense orientation. Furthermore, the antisense insertion resulted in higher accumulation of the colorless carotenoid phytoene compared to the sense orientation. Our results indicate that the gene fragments inserted using the antisense orientation induced higher gene silencing than the sense orientation because more short interfering RNAs were produced. These siRNAs are complementary to the mRNAs of the target gene and consequently guide the degradation of target mRNA. Better understanding of gene silencing mechanisms in plants is necessary to enhance VIGS technology.

Accumulation of carotenoids in a novel citrus cultivar 'Seinannohikari' during the fruit maturation

In the present study, carotenoid metabolism was investigated in the fruits of a novel citrus cultivar, 'Seinannohikari' (Citrus spp.). During the maturation, β,β-xanthophylls were accumulated rapidly with β-cryptoxanthin being the dominant carotenoid compound in the flavedo and juice sacs of 'Seinannohikari'. In the juice sacs of mature fruits, 'Seinannohikari' accumulated high amount of carotenoids, especially β-cryptoxanthin. The content of β-cryptoxanthin in the juice sacs of 'Seinannohikari' was approximately 2.5 times of that in 'Miyagawa-wase' (Citrus unshiu), which is one of its parental cultivars, at the mature stage. Gene expression results showed that the massive accumulation of β-cryptoxanthin might be attributed to the higher expression of carotenoid biosynthetic genes (CitPSY, CitPDS, CitZDS, CitLCYb2, CitHYb, and CitZEP), and lower expression of carotenoid catabolic genes (CitNCED2 and CitNCED3) in the juice sacs of 'Seinannohikari'.

Expression of Carotenoid Biosynthetic Genes and Carotenoid Biosynthesis during Seedling Development of Momordica charantia

Carotenoids belong to a large group of secondary metabolites, and have pivotal roles in plants, including photosynthesis and phytohormone synthesis, pigmentation, and membrane stabilization. Additionally, carotenoids are potent antioxidants, and their health benefits are becoming increasingly prominent. In recent years, carotenoids have been studied in many plants. Furthermore, gene expression, as well as carotenoid accumulation in different parts of the bitter melon, has been investigated; however, it has not been studied in bitter melon seedlings. In this study, carotenoid accumulation and transcript levels of McGGPPS1, McGGPPS2, McPSY, McPDS, McZDS, McLCYB, McLCYE1, McLCYE2, McCXHB, and McZEP, involved in carotenoid biosynthesis, were analyzed during seedling development using HPLC and qRT-PCR. The major carotenoids that accumulated in the bitter melon seedlings were lutein and E-β-carotene. The expression of most carotenoid biosynthetic genes increased during seedling development, consistent with the accumulation of violaxanthin, lutein, zeaxanthin, β-cryptoxanthin, 13Z-β-carotene, E-β-carotene, and 9Z-β-carotene in bitter melon seedlings. The results of this study provide a firm basis for comprehending the link between gene expression and carotenoid concentration in bitter melon seedlings.

A Study on the Expression of Genes Involved in Carotenoids and Anthocyanins During Ripening in Fruit Peel of Green, Yellow, and Red Colored Mango Cultivars.

Mango (Mangiferaindica L.) fruits are generally classified based on peel color into green, yellow, and red types. Mango peel turns from green to yellow or red or retain green colors during ripening. The carotenoids and anthocyanins are the important pigments responsible for the colors of fruits. In the present study, peels of different colored cultivars at three ripening stages were characterized for pigments, colors, and gene expression analysis. The yellow colored cultivar "Arka Anmol" showed higher carotenoid content, wherein β-carotene followed by violaxanthin were the major carotenoid compounds that increased during ripening. The red colored cultivars were characterized with higher anthocyanins with cyanidin-3-O-monoglucosides and peonidin-3-O-glucosides as the major anthocyanins. The gene expression analysis by qRT-PCR showed the higher expression of carotenoid biosynthetic genes viz. lycopene-β-cyclase and violaxanthin-de-epoxidase in yellow colored cv. Arka Anmol, and the expression was found to increase during ripening. However, in red colored cv. "Janardhan Pasand," there is increased regulation of all anthocyanin biosynthetic genes including transcription factors MYB and basic helix loop. This indicated the regulation of the anthocyanins by these genes in red mango peel. The results showed that the accumulation pattern of particular pigments and higher expression of specific biosynthetic genes in mango peel impart different colors.

Carotenoid Biosynthetic Pathways Are Regulated by a Network of Multiple Cascades of Alternative Sigma Factors in Azospirillum brasilense Sp7.

Carotenoids play a very important role in coping with photooxidative stress in prokaryotes and eukaryotes. Although extracytoplasmic function (ECF) sigma factors are known to directly regulate the expression of carotenoid biosynthetic genes in bacteria, regulation of carotenoid biosynthesis by one or multiple cascades of sigma factors had not been reported. This study provides the first evidence of the involvement of multiple cascades of sigma factors in the regulation of carotenoid synthesis in any bacterium by showing the regulation of a gene encoding geranylgeranyl pyrophosphate synthase (crtE2) by RpoE1→RpoH2→CrtE2 and RpoE2→RpoH1→CrtE2 cascades in A. brasilense It also provides an insight into existence of an additional cascade or cascades regulating expression of another paralog of crtE.

Diversity in the carotenoid profiles and the expression of genes related to carotenoid accumulation among citrus genotypes.

Carotenoids are not only important to the plants themselves but also are beneficial to human health. Since citrus fruit is a good source of carotenoids for the human diet, it is important to study carotenoid profiles and the accumulation mechanism in citrus fruit. Thus, in the present paper, we describe the diversity in the carotenoid profiles of fruit among citrus genotypes. In regard to carotenoids, such as β-cryptoxanthin, violaxanthin, lycopene, and β-citraurin, the relationship between the carotenoid profile and the expression of carotenoid-biosynthetic genes is discussed. Finally, recent results of quantitative trait locus (QTL) analyses of carotenoid contents and expression levels of carotenoid-biosynthetic genes in citrus fruit are shown.

Overexpression of a citrus basic helix-loop-helix transcription factor (CubHLH1), which is homologous to Arabidopsis activation-tagged bri1 suppressor 1 interacting factor genes, modulates carotenoid metabolism in transgenic tomato

To explore the transcription factors associated with carotenoid metabolism in citrus fruit, one transcription factor (CubHLH1) was selected through microarray screening in Satsuma mandarin (Citrus unshiu Marc.) fruit, which was treated with exogenous ethylene or gibberellin (GA), accelerating or retarding carotenoid accumulation in peel, respectively. The amino acid sequence of CubHLH1 has homology to Arabidopsis activation-tagged bri1 suppressor 1 (ATBS1) interacting factor (AIF), which is functionally characterized as a negative regulator of the brassinolide (BR) signalling pathway. Yeast two-hybrid analysis revealed that protein for CubHLH1 could interact with Arabidopsis and tomato ATBS1. Overexpression of CubHLH1 caused a dwarf phenotype in transgenic tomato (Solanum lycopersicum L.), suggesting that CubHLH1 has a similar function to Arabidopsis AIF. In the transgenic tomato fruit at ripening stage, the lycopene content was reduced along with the changes in carotenoid biosynthetic gene expression. The abscisic acid (ABA) content of all the transgenic tomato fruit was higher than that of the wild type. These results implied that CubHLH1 is considered to have a similar function to Arabidopsis AIFs and might be directly involved in carotenoid metabolism in mature citrus fruit.

Fruit shading enhances peel color, carotenes accumulation and chromoplast differentiation in red grapefruit.

The distinctive color of red grapefruits is due to lycopene, an unusual carotene in citrus. It has been observed that red 'Star Ruby' (SR) grapefruits grown inside the tree canopy develop a more intense red coloration than those exposed to higher light intensities. To investigate the effect of light on SR peel pigmentation, fruit were bagged or exposed to normal photoperiodic conditions, and changes in carotenoids, expression of carotenoid biosynthetic genes and plastid ultrastructure in the peel were analyzed. Light avoidance accelerated chlorophyll breakdown and induced carotenoid accumulation, rendering fruits with an intense coloration. Remarkably, lycopene levels in the peel of shaded fruits were 49-fold higher than in light-exposed fruit while concentrations of downstream metabolites were notably reduced, suggesting a bottleneck at the lycopene cyclization in the biosynthetic pathway. Paradoxically, this increment in carotenoids in covered fruit was not mirrored by changes in mRNA levels of carotenogenic genes, which were mostly up-regulated by light. In addition, covered fruits experienced profound changes in chromoplast differentiation, and the relative expression of genes related to chromoplast development was enhanced. Ultrastructural analysis of plastids revealed an acceleration of chloroplasts to chromoplast transition in the peel of covered fruits concomitantly with development of lycopene crystals and plastoglobuli. In this sense, an accelerated differentiation of chromoplasts may provide biosynthetic capacity and a sink for carotenoids without involving major changes in transcript levels of carotenogenic genes. Light signals seem to regulate carotenoid accumulation at the molecular and structural level by influencing both biosynthetic capacity and sink strength.

収穫したカラーピーマン果実に対する光照射に伴うカロテノイド生合成関連遺伝子の発現変化

カラーピーマン果実の着色に伴うカロテノイド生合成関連遺伝子の発現と，収穫した果実に対する光照射処理の影響を調べた．成熟が開始した果実を収穫して，光合成光量子束密度が100 μmol・m−2・s−1の光を照射した．1日間の光照射で，phytoene synthase（Psy），β-carotene hydroxylase（CrtZ-2）とcapsanthin/capsorubin synthase（Ccs）は顕著に遺伝子発現量が増加した．それぞれの発現量は，対照の暗黒処理よりも207倍，8倍と6倍多く発現していた．他のカロテノイド生合成関連遺伝子，phytoene desaturase（Pds），ζ-carotene desaturase（Zds），lycopene β-cyclase（LcyB），zeaxanthin epoxidase（Ze），violaxanthin de-epoxidase（Vde）も，それぞれ暗黒の対照に比べて2～3倍高かった．光照射した果実は，5日間で全体が赤くなった．これらの結果から，収穫した果実に対する光照射処理がPsyとともに，CrtZ-2, Ccsなど他のカロテノイド生合成関連遺伝子の発現を増大させ，capsanthinの蓄積を促進するものと考えられた．