beta-carotene and ethylene

ETHYLENE-INSENSITIVE 3/ETHYLENE-INSENSITIVE 3-LIKEs (EIN3/EILs) are important ethylene response factors during fruit ripening. Here, we discovered that EIL2 controls carotenoid metabolism and ascorbic acid (AsA) biosynthesis in tomato (Solanum lycopersicum). In contrast to the red fruits presented in the wild type (WT) 45 d after pollination, the fruits of CRISPR/Cas9 eil2 mutants and SlEIL2 RNA interference lines (ERIs) showed yellow or orange fruits. Correlation analysis of transcriptome and metabolome data for the ERI and WT ripe fruits revealed that SlEIL2 is involved in β-carotene and AsA accumulation. ETHYLENE RESPONSE FACTORs (ERFs) are the typical components downstream of EIN3 in the ethylene response pathway. Through a comprehensive screening of ERF family members, we determined that SlEIL2 directly regulates the expression of 4 SlERFs. Two of these, SlERF.H30 and SlERF.G6, encode proteins that participate in the regulation of LYCOPENE-β-CYCLASE 2 (SlLCYB2), encoding an enzyme that mediates the conversion of lycopene to carotene in fruits. In addition, SlEIL2 transcriptionally repressed L-GALACTOSE 1-PHOSPHATE PHOSPHATASE 3 (SlGPP3) and MYO-INOSITOL OXYGENASE 1 (SlMIOX1) expression, which resulted in a 1.62-fold increase of AsA via both the L-galactose and myoinositol pathways. Overall, we demonstrated that SlEIL2 functions in controlling β-carotene and AsA levels, providing a potential strategy for genetic engineering to improve the nutritional value and quality of tomato fruit.

Topics: Ascorbic Acid; beta Carotene; Ethylenes; Fruit; Galactose; Gene Expression Regulation, Plant; Lycopene; Plant Proteins; Solanum lycopersicum

Carotenoid content in durian (Durio zibethinus) fruit is an important aspect of fruit quality, with different cultivars distinguished by differing pigmentation. We have studied the dependence of carotenogenesis on ethylene. Fruit of the cultivar 'Chanee' harvested at the mature stage were either left untreated (controls), treated with 1-methylcyclopropene (1-MCP) for 12 h, or treated with application of an aqueous ethephon solution to the stem end, or treated for 12 h with 1-MCP followed by ethephon application. Fruit were then stored for 9 d at 25 °C. Pulp color of durian became steadily yellowish as a result of accumulation of carotenoids, which were mainly beta-carotene, and alpha-carotene, with a minor amount of zeaxanthin and lutein. 1-MCP delayed the increase in the accumulation of beta-carotene, alpha-carotene, and zeaxanthin, but not lutein. In contrast, ethephon had no significant effect on carotenoid accumulation. The expression of zeta-carotene desaturase (ZDS), lycopene beta-cyclase (LCYB), chromoplast specific lycopene beta-cyclase (CYCB) and beta-carotene hydroxylase (BCH) genes was highly correlated with carotenoid content and pulp color.1-MCP resulted in significant down-regulation of ZDS, LCYB, CYCB and BCH expression. The accumulation of beta-carotene and alpha-carotene appears to be controlled by the level of expression of LCYB gene, whose function was tested in bacteria to show conversion of lycopene and delta-carotene to beta-carotene and alpha-carotene, respectively. These results suggest that ripening-induced carotenoid accumulation is regulated by endogenous ethylene controlling the expression of key genes such as LCYB.

Topics: beta Carotene; Bombacaceae; Carotenoids; Cyclopropanes; Ethylenes; Fruit; Gene Expression Regulation, Plant; Lycopene; Plant Proteins

Fruit ripening involves a complex interplay between ethylene and ripening-associated transcriptional regulators. Ethylene Response Factors (ERFs) are downstream components of ethylene signaling, known to regulate the expression of ethylene-responsive genes. Although fruit ripening is an ethylene-regulated process, the role of ERFs remains poorly understood. The role of Sl-ERF.B3 in tomato (Solanum lycopersicum) fruit maturation and ripening is addressed here using a chimeric dominant repressor version (ERF.B3-SRDX). Over-expression of ERF.B3-SRDX results in a dramatic delay of the onset of ripening, enhanced climacteric ethylene production and fruit softening, and reduced pigment accumulation. Consistently, genes involved in ethylene biosynthesis and in softening are up-regulated and those of carotenoid biosynthesis are down-regulated. Moreover, the expression of ripening regulators, such as RIN, NOR, CNR and HB-1, is stimulated in ERF.B3-SRDX dominant repressor fruits and the expression pattern of a number of ERFs is severely altered. The data suggest the existence of a complex network enabling interconnection between ERF genes which may account for the pleiotropic alterations in fruit maturation and ripening. Overall, the study sheds new light on the role of Sl-ERF.B3 in the transcriptional network controlling the ripening process and uncovers a means towards uncoupling some of the main ripening-associated processes.

Topics: beta Carotene; Carotenoids; Ethylenes; Fruit; Gene Expression Profiling; Gene Expression Regulation, Plant; Lycopene; Phenotype; Plant Proteins; Plants, Genetically Modified; Repressor Proteins; Solanum lycopersicum; Transcription Factors

In this study, the pathway of β-citraurin biosynthesis, carotenoid contents and the expression of genes related to carotenoid metabolism were investigated in two varieties of Satsuma mandarin (Citrus unshiu), Yamashitabeni-wase, which accumulates β-citraurin predominantly, and Miyagawa-wase, which does not accumulate β-citraurin. The results suggested that CitCCD4 (for Carotenoid Cleavage Dioxygenase4) was a key gene contributing to the biosynthesis of β-citraurin. In the flavedo of Yamashitabeni-wase, the expression of CitCCD4 increased rapidly from September, which was consistent with the accumulation of β-citraurin. In the flavedo of Miyagawa-wase, the expression of CitCCD4 remained at an extremely low level during the ripening process, which was consistent with the absence of β-citraurin. Functional analysis showed that the CitCCD4 enzyme exhibited substrate specificity. It cleaved β-cryptoxanthin and zeaxanthin at the 7,8 or 7',8' position. But other carotenoids tested in this study (lycopene, α-carotene, β-carotene, all-trans-violaxanthin, and 9-cis-violaxanthin) were not cleaved by the CitCCD4 enzyme. The cleavage of β-cryptoxanthin and zeaxanthin by CitCCD4 led to the formation of β-citraurin. Additionally, with ethylene and red light-emitting diode light treatments, the gene expression of CitCCD4 was up-regulated in the flavedo of Yamashitabeni-wase. These increases in the expression of CitCCD4 were consistent with the accumulation of β-citraurin in the two treatments. These results might provide new strategies to improve the carotenoid contents and compositions of citrus fruits.

Topics: beta Carotene; Carotenoids; Chromatography, High Pressure Liquid; Citrus; Cryptoxanthins; Dioxygenases; DNA, Complementary; Ethylenes; Gene Expression Regulation, Plant; Genes, Plant; Green Fluorescent Proteins; Light; Metabolic Networks and Pathways; Molecular Sequence Data; Nicotiana; Plant Leaves; Plants, Genetically Modified; Recombinant Fusion Proteins; Subcellular Fractions; Xanthophylls; Zeaxanthins

Abscisic acid (ABA) plays important roles during tomato fruit ripening. To study the regulation of carotenoid biosynthesis by ABA, the SlNCED1 gene encoding 9-cis-epoxycarotenoid dioxygenase (NCED), a key enzyme in the ABA biosynthesis, was suppressed in tomato plants by transformation with an RNA interference (RNAi) construct driven by a fruit-specific E8 promoter. ABA accumulation and SlNCED1 transcript levels in the transgenic fruit were down-regulated to between 20-50% of that in control fruit. This significant reduction in NCED activity led to the carbon that normally channels to free ABA as well as the ABA metabolite accumulation during ripening to be partially blocked. Therefore, this 'backlogged' carbon transformed into the carotenoid pathway in the RNAi lines resulted in increased assimilation and accumulation of upstream compounds in the pathway, chiefly lycopene and β-carotene. Fruit of all RNAi lines displayed deep red coloration compared with the pink colour of control fruit. The decrease in endogenous ABA in these transgenics resulted in an increase in ethylene, by increasing the transcription of genes related to the synthesis of ethylene during ripening. In conclusion, ABA potentially regulated the degree of pigmentation and carotenoid composition during ripening and could control, at least in part, ethylene production and action in climacteric tomato fruit.

Topics: Abscisic Acid; beta Carotene; Carotenoids; Dioxygenases; Ethylenes; Fruit; Gene Expression Regulation, Plant; Genes, Plant; Lycopene; Organ Specificity; Plant Proteins; Plants, Genetically Modified; RNA Interference; Signal Transduction; Solanum lycopersicum; Suppression, Genetic; Up-Regulation

The effect of UV-B shielding on ethylene production in ripening tomato fruits and the contribution of ethylene and UV-B radiation on carotenoid accumulation and profile during ripening were assessed to get more insight about the interplay between these two regulatory factors. To this aim, rin and nor tomato mutants, unable to produce ripening ethylene, and cv Ailsa Craig were cultivated under control or UV-B depleted conditions until full fruit ripening. The significantly decreased ethylene evolution following UV-B depletion, evident only in Ailsa Craig, suggested the requirement of functional rin and nor genes for UVB-mediated ethylene production. Carotenoid content and profile were found to be controlled by both ethylene and UV-B radiation. This latter influenced carotenoid metabolism either in an ethylene-dependent or -independent way, as indicated by UVB-induced changes also in nor and rin carotenoid content and confirmed by correlation plots between ethylene evolution and carotenoid accumulation performed separately for control and UV-B shielded fruits. In conclusion, natural UV-B radiation influences carotenoid metabolism in a rather complex way, involving ethylene-dependent and -independent mechanisms, which seem to act in an antagonistic way.

Topics: beta Carotene; Carotenoids; Chlorophyll; Ethylenes; Fruit; Lutein; Mutation; Solanum lycopersicum; Sunlight; Ultraviolet Rays

Tomato (Solanum lycopersicum) fruit ripening is characterized by a massive accumulation of carotenoids (mainly lycopene) as chloroplasts change to chromoplasts. To address the question of the role of sugars in controlling carotenoid accumulation, fruit pericarp discs (mature green fruits) were cultured in vitro in the presence of various sucrose concentrations. A significant difference in soluble sugar content was achieved depending on external sucrose availability. Sucrose limitation delayed and reduced lycopene and phytoene accumulation, with no significant effect on other carotenoids. Chlorophyll degradation and starch catabolism were not affected by variations of sucrose availability. The reduction of lycopene synthesis observed in sucrose-limited conditions was mediated through metabolic changes illustrated by reduced hexose accumulation levels. In addition, variations of sucrose availability modulated PSY1 gene expression. Taken together our results suggest that the modulation of carotenoid accumulation by sucrose availability occurs at the metabolic level and involves the differential regulation of genes involved in carotenoid biosynthesis.

Topics: Base Sequence; beta Carotene; Carotenoids; Chromatography, High Pressure Liquid; DNA Primers; Ethylenes; Gene Expression Regulation, Plant; Lycopene; Magnetic Resonance Spectroscopy; Reverse Transcriptase Polymerase Chain Reaction; RNA, Plant; Signal Transduction; Solanum lycopersicum; Sucrose