The dominant allele Aft induces a shift from flavonol to anthocyanin production in response to UV-B radiation in tomato fruit

The introgression of the A ft allele into domesticated tomato induced a shift from flavonol to anthocyanin production in response to UV-B radiation, while the hp - 1 allele negatively influenced the response of flavonoid biosynthesis to UV-B. Introgression of the dominant allele Anthocyanin fruit (Aft) from Solanum chilense induces anthocyanin accumulation in the peel of tomato (Solanum lycopersicum L.) fruit. UV-B radiation can influence plant secondary metabolism regulating the expression of several genes, among which those involved in flavonoid biosynthesis. Here, we investigated whether post-harvest UV-B treatment could up-regulate flavonoid production in tomato fruits and whether the Aft allele could affect flavonoid biosynthesis under UV-B radiation. Mature green fruits of an anthocyanin-rich tomato mutant line (SA206) and of its wild-type reference, cv. Roma, were daily subjected to post-harvest UV-B treatment until full ripening. Up-regulation of CHS and CHI transcription by UV-B treatment induced flavonoid accumulation in the peel of cv. Roma. Conversely, UV-B decreased the total flavonoid content and CHS transcript levels in the SA206 peel. SA206 being a double mutant containing also hp-1 allele, we investigated also the behavior of hp-1 fruit. The decreased peel flavonoid accumulation and gene transcription in response to UV-B suggest that hp-1 allele is involved in the marked down-regulation of the flavonoid biosynthesis observed in SA206 fruit. Interestingly, in SA206, UV-B radiation promoted the synthesis of delphinidin, petunidin, and malvidin by increasing F3'5'H and DFR transcription, but it decreased rutin production, suggesting a switch from flavonols to anthocyanins. Finally, although UV-B radiation does not reach the inner fruit tissues, it down-regulated flavonoid biosynthesis in the flesh of both genotypes. This study provides, for the first time, evidence that the presence of the functional Aft allele, under UV-B radiation, redirects flavonoid synthesis towards anthocyanin production and suggests that the hp-1 allele negatively influences the response of flavonoid biosynthesis to UV-B.

Dietary cyanidin 3-glucoside from purple corn ameliorates doxorubicin-induced cardiotoxicity in mice

BACKGROUND AND AIMS

Anthracyclines are effective anticancer drugs that have improved prognosis of hundred thousand cancer patients worldwide and are currently the most common chemotherapeutic agents used for the treatment of blood, breast, ovarian and lung cancers. However, their use is limited because of a cumulative dose-dependent and irreversible cardiotoxicity that can cause progressive cardiomyopathy and congestive heart failure. Aim of the present study was to determine the cardioprotective activity of a dietary source of cyanidin 3-glucoside (C3G), such as purple corn, against doxorubicin (DOX)-induced cardiotoxicity in mice.

METHODS AND RESULTS

In vitro studies on murine HL-1 cardiomyocytes showed that pretreatment with both pure C3G and purple corn extract improved survival upon DOX treatment. However, C3G and purple corn extract did not affect the cytotoxic effect of DOX on human cancer cell lines. We then validated in vivo the protective role of a C3G-enriched diet against DOX-induced cardiotoxicity by comparing the effect of dietary consumption of corn isogenic lines with high levels of anthocyanins (purple corn - Red diet - RD) or without anthocyanins (yellow corn - Yellow diet - YD) incorporated in standard rodent diets. Results showed that mice fed RD survived longer than mice fed YD upon injection of a toxic amount of DOX. In addition, ultrastructural analysis of hearts from mice fed RD showed reduced histopathological alterations.

CONCLUSION

Dietary intake of C3G from purple corn protects mice against DOX-induced cardiotoxicity.

The Arabidopsis NF-YA3 and NF-YA8 genes are functionally redundant and are required in early embryogenesis

Nuclear factor Y (NF-Y) is a trimeric transcription factor composed of three distinct subunits called NF-YA, NF-YB and NF-YC. In Arabidopsis thaliana, NF-Y subunits are known to play roles in many processes, such as gametogenesis, embryogenesis, seed development, drought resistance, ABA signaling, flowering time, primary root elongation, Endoplasmic Reticulum (ER) stress response and blue light responses. Here, we report that the closely related NF-YA3 and NF-YA8 genes control early embryogenesis. Detailed GUS and in situ analyses showed that NF-YA3 and NF-YA8 are expressed in vegetative and reproductive tissues with the highest expression being during embryo development from the globular to the torpedo embryo stage. Plants from the nf-ya3 and nf-ya8 single mutants do not display any obvious phenotypic alteration, whereas nf-ya3 nf-ya8 double mutants are embryo lethal. Morphological analyses showed that the nf-ya3 nf-ya8 embryos fail to undergo to the heart stage and develop into abnormal globular embryos with both proembryo and suspensor characterized by a disordered cell cluster with an irregular shape, suggesting defects in embryo development. The suppression of both NF-YA3 and NF-YA8 gene expression by RNAi experiments resulted in defective embryos that phenocopied the nf-ya3 nf-ya8 double mutants, whereas complementation experiments partially rescued the abnormal globular nf-ya3 nf-ya8 embryos, confirming that NF-YA3 and NF-YA8 are required in early embryogenesis. Finally, the lack of GFP expression of the auxin responsive DR5rev::GFP marker line in double mutant embryos suggested that mutations in both NF-YA3 and NF-YA8 affect auxin response in early developing embryos. Our findings indicate that NF-YA3 and NF-YA8 are functionally redundant genes required in early embryogenesis of Arabidopsis thaliana.

The promiscuous life of plant NUCLEAR FACTOR Y transcription factors

The CCAAT box is one of the most common cis-elements present in eukaryotic promoters and is bound by the transcription factor NUCLEAR FACTOR Y (NF-Y). NF-Y is composed of three subunits, NF-YA, NF-YB, and NF-YC. Unlike animals and fungi, plants have significantly expanded the number of genes encoding NF-Y subunits. We provide a comprehensive classification of NF-Y genes, with a separation of closely related, but distinct, histone fold domain proteins. We additionally review recent experiments that have placed NF-Y at the center of many developmental stress-responsive processes in the plant lineage.

Carotenoid profiling and biosynthetic gene expression in flesh and peel of wild-type and hp-1 tomato fruit under UV-B depletion

Although light is recognized as one of the main factors influencing fruit carotenogenesis, the specific role of UV-B radiation has been poorly investigated. The present work is addressed to assess the molecular events underlying carotenoid accumulation in presence or absence of ultraviolet-B (UV-B) light in tomato fruits of wild-type and high pigment-1 (hp-1), a mutant characterized by exaggerated photoresponsiveness and increased fruit pigmentation. Gene expression analyses indicated that in wild-type fruits UV-B radiation mainly negatively affects the carotenoid biosynthetic genes encoding enzymes downstream of lycopene both in flesh and peel, suggesting that the down-regulation of genes CrtL-b and CrtL-e and the subsequent accumulation of lycopene during tomato ripening are determined at least in part by UV-B light. In contrast to wild-type, UV-B depletion did not greatly affect carotenoid accumulation in hp-1 and generally determined minor differences in gene expression between control and UV-B-depleted conditions.

Identification and expression profiling of Ceratitis capitata genes coding for β-hexosaminidases

The goal of this study was to identify the genes coding for β-N-acetylhexosaminidases in the Mediterranean fruit fly (medfly) Ceratitis capitata, one of the most destructive agricultural pests, belonging to the Tephritidae family, order Diptera. Two dimeric β-N-acetylhexosaminidases, HEXA and HEXB, have been recently identified on Drosophila sperm. These enzymes are involved in egg binding through interactions with complementary carbohydrates on the surface of the egg shell. Three genes, Hexosaminidase 1 (Hexo1), Hexosaminidase 2 (Hexo2) and fused lobes (fdl), encode for HEXA and HEXB subunits. The availability of C. capitata EST libraries derived from embryos and adult heads allowed us to identify three sequences homologous to the D. melanogaster Hexo1, Hexo2 and fdl genes. Here, we report the expression profile analysis of CcHexo1, CcHexo2 and Ccfdld in several tissues, organs and stages. Ccfdl expression was highest in heads of both sexes and in whole adult females. In the testis and ovary the three genes showed distinct spatial and temporal expression patterns. All the mRNAs were detectable in early stages of spermatogenesis; CcHexo2 and Ccfdl were also expressed in early elongating spermatid cysts. All three genes are expressed in the ovarian nurse cells. CcHexo1 and Ccfdl are stage specific, since they have been observed in stages 12 and 13 during oocyte growth, when programmed cell death occurs in nurse cells. The expression pattern of the three genes in medfly gonads suggests that, as their Drosophila counterparts, they may encode for proteins involved in gametogenesis and fertilization.

Response of wild-type and high pigment-1 tomato fruit to UV-B depletion: flavonoid profiling and gene expression

The tomato high pigment-1 (hp-1) mutant is characterised by exaggerated photoresponsiveness and increased fruit pigmentation, and carries a mutation in the HP1/LeDDB1 gene, encoding the tomato homologue of the negative regulator of the light signal transduction DDB1a from Arabidopsis. Here, we investigated the molecular events underlying flavonoid accumulation in flesh and peel of wild-type and hp-1 fruits in presence or absence of UV-B light. In hp-1 peel, a twofold higher level of rutin and an earlier accumulation of flavonoids than in wild-type were observed, which correlated to the earlier activation of most flavonoid biosynthetic genes compared to wild-type. In hp-1 flesh, flavonoid content was up to 8.5-fold higher than in wild-type and correlated to the higher transcript level of flavonoid genes compared to wild-type. In both tissues, the expression of flavonoid genes was correlated with the anticipated and/or enhanced activation of the light signal transduction genes: LeCOP1LIKE, LeCOP1 and LeHY5. In wild-type, flavonoid content was severely reduced by UV-B depletion mostly in peel, whereas in hp-1 it was significantly increased in flesh. The activation of flavonoid and light signal transduction genes was UV-B dependent mostly at the mature green stage, whereas LeDDB1 expression was not regulated by UV-B.

Solar UV-B radiation influences carotenoid accumulation of tomato fruit through both ethylene-dependent and -independent mechanisms

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.

Flavonoid profiling and biosynthetic gene expression in flesh and peel of two tomato genotypes grown under UV-B-depleted conditions during ripening

The effect of shielding solar ultraviolet B radiation on the accumulation of some flavonoids and their precursor hydroxycinnamic acids in tomato (Solanum lycopersicum) was evaluated by liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). In particular, flesh and peel of two tomato hybrids, DRW 5981 and Esperanza, were separately analyzed. The hybrids have been chosen for their different responses to the light, since it was previously reported that they show different pigmentation and opposite behavior under UV-B in terms of carotenoids and ascorbic acid content at different ripening stages. To determine the effect of UV-B radiation during tomato ripening, we also measured the expression of some flavonoid biosynthetic genes by real-time reverse transcription-polymerase chain reaction (RT-PCR) analysis. The results allowed us to conclude that UV-B radiation deeply and differentially affects the content of the considered flavonoids and hydroxycinnamic acids as well as the expression of some of their biosynthetic genes in both flesh and peel during the ripening process. On the other hand, the collected data clearly showed that this influence varies between different genotypes. We conclude that the use of specific plastic covers able to eliminate UV-B radiation may be an environmentally friendly approach to modulate the expression of structural genes and, in turn, to enhance healthy antioxidant compounds in fruits of specific tomato cultivars.

The AtMYB11 gene from Arabidopsis is expressed in meristematic cells and modulates growth in planta and organogenesis in vitro

In plants, MYB transcription factors play important roles in many developmental processes including cell cycle progression, cell differentiation, and lateral organ polarity. It is shown here that the R2R3-MYB AtMYB11 gene is expressed in root and shoot meristems and also in young still meristematic leaf and flower primordia of Arabidopsis. Knock-out atmyb11-I mutants and RNAi plants germinate faster, show a faster hypocotyl and primary root elongation, develop more lateral and adventitious roots, show faster development of the inflorescence, and initiate more lateral inflorescences and fruits than wild-type plants. The opposite phenotype was displayed by plants overexpressing AtMYB11. De novo formation of root meristemoids and, consequently, macroscopic roots, from thin cell layers cultured in vitro was enhanced in explants from atmyb11-I and reduced in those from lines overexpressing AtMYB11. These findings indicate that AtMYB11 modulates overall growth in plants by reducing the proliferation activity of meristematic cells and delaying plant development.