Four sequence positions of the movement protein of Cucumber mosaic virus determine the virulence against cmv1-mediated resistance in melon.

The resistance to a set of strains of Cucumber mosaic virus (CMV) in the melon accession PI 161375, cultivar 'Songwhan Charmi', is dependent on one recessive gene, cmv1, which confers total resistance, whereas a second set of strains is able to overcome it. We tested 11 strains of CMV subgroups I and II in the melon line SC12-1-99, which carries the gene cmv1, and showed that this gene confers resistance to strains of subgroup II only and that restriction is not related to either viral replication or cell-to-cell movement. This is the first time that a resistant trait has been correlated with CMV subgroups.

The HY5-PIF regulatory module coordinates light and temperature control of photosynthetic gene transcription.

The ability to interpret daily and seasonal alterations in light and temperature signals is essential for plant survival. This is particularly important during seedling establishment when the phytochrome photoreceptors activate photosynthetic pigment production for photoautotrophic growth. Phytochromes accomplish this partly through the suppression of phytochrome interacting factors (PIFs), negative regulators of chlorophyll and carotenoid biosynthesis.

Quantification of plant resistance to isoprenoid biosynthesis inhibitors.

Plants use two pathways for the production of the same universal isoprenoid precursors: the mevalonic acid (MVA) pathway and the methylerythritol 4-phosphate (MEP) pathway. Inhibitors of the MVA pathway prevent the activity of the shoot apical meristem and the development of true leaves in seedlings, whereas those inhibiting the MEP pathway show an additional bleaching phenotype. Here, we describe two methods to quantify plant resistance to inhibitors of the MVA pathway or the MEP pathway based on seedling establishment and photosynthetic pigment measurements.

Confocal laser scanning microscopy detection of chlorophylls and carotenoids in chloroplasts and chromoplasts of tomato fruit.

Plant cells are unique among eukaryotic cells because of the presence of plastids, including chloroplasts and chromoplasts. Chloroplasts are found in green tissues and harbor the photosynthetic machinery (including chlorophyll molecules), while chromoplasts are present in non-photosynthetic tissues and accumulate large amounts of carotenoids. During tomato fruit development, chloroplasts are converted into chromoplasts that accumulate high levels of lycopene, a linear carotenoid responsible for the characteristic red color of ripe fruit.

A root specific induction of carotenoid biosynthesis contributes to ABA production upon salt stress in arabidopsis.

Abscisic acid (ABA) is a hormone that plays a vital role in mediating abiotic stress responses in plants. Salt exposure induces the synthesis of ABA through the cleavage of carotenoid precursors (xanthophylls), which are found at very low levels in roots. Here we show that de novo ABA biosynthesis in salt-treated Arabidopsis thaliana roots involves an organ-specific induction of the carotenoid biosynthetic pathway.

The genetic basis of fruit morphology in horticultural crops: lessons from tomato and melon.

Fruits represent an important part of the human diet and show extensive variation in size and shape between and within cultivated species. The genetic basis of such variation has been studied most extensively in tomato, where currently six quantitative trait loci (QTLs) involving these traits have been fine-mapped and the genes underlying the QTLs identified. The genes responsible for the cloned QTLs belong to families with a few to many members.

Identification of a type I Ca2+/Mg2+-dependent endonuclease induced in maize cells exposed to camptothecin.

Background: Camptothecin is a plant alkaloid that specifically binds topoisomerase I, inhibiting its activity and inducing double stranded breaks in DNA and activating the cell responses to DNA damage.

Results: Maize cultured cells were incubated in the presence of different concentrations of camptothecin. Camptothecin inhibits cultured cell growth, induces genomic DNA degradation, and induces a 32 kDa Ca2+/Mg2+-dependent nuclease activity.

Biosynthesis of carotenoids in carrot: an underground story comes to light.

Carrot (Daucus carota) is a biannual plant that accumulates massive amounts of carotenoid pigments in the storage root. Although the root of carrot plants was white before domestication, intensive breeding generated the currently known carotenoid-rich varieties, including the widely popular orange carrots that accumulate very high levels of the pro-vitamin A carotenoids β-carotene and, to a lower extent, α-carotene. Recent studies have shown that the developmental program responsible for the accumulation of these health-promoting carotenes in underground roots can be completely altered when roots are exposed to light.

Metabolic plasticity for isoprenoid biosynthesis in bacteria.

Isoprenoids are a large family of compounds synthesized by all free-living organisms. In most bacteria, the common precursors of all isoprenoids are produced by the MEP (methylerythritol 4-phosphate) pathway. The MEP pathway is absent from archaea, fungi and animals (including humans), which synthesize their isoprenoid precursors using the completely unrelated MVA (mevalonate) pathway.

Interaction between QTLs induces an advance in ethylene biosynthesis during melon fruit ripening.

The coexistence of both climacteric and non-climacteric genotypes and the availability of a set of genetic and genomic resources make melon a suitable model for genetic studies of fruit ripening. We have previously described a QTL, ETHQB3.5, which induces climacteric fruit ripening in the near-isogenic line (NIL) SC3-5 that harbors an introgression on linkage group (LG) III from the non-climacteric melon accession PI 161375 in the, also non-climacteric cultivar, "Piel de Sapo" genetic background.

Plant integrity: an important factor in plant-pathogen interactions.

The effect of plant integrity and of aboveground-belowground defense signaling on plant resistance against pathogens and herbivores is emerging as a subject of scientific research. There is increasing evidence that plant defense responses to pathogen infection differ between whole intact plants and detached leaves. Studies have revealed the importance of aboveground-belowground defense signaling for plant defenses against herbivores, while our studies have uncovered that the roots as well as the plant integrity are important for the resistance of the potato cultivar Sarpo Mira against the hemibiotrophic oomycete pathogen Phytophthora infestans.

Characterization of Arabidopsis FPS isozymes and FPS gene expression analysis provide insight into the biosynthesis of isoprenoid precursors in seeds.

Arabidopsis thaliana contains two genes encoding farnesyl diphosphate (FPP) synthase (FPS), the prenyl diphoshate synthase that catalyzes the synthesis of FPP from isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP). In this study, we provide evidence that the two Arabidopsis short FPS isozymes FPS1S and FPS2 localize to the cytosol. Both enzymes were expressed in E.

Mutations in Escherichia coli aceE and ribB genes allow survival of strains defective in the first step of the isoprenoid biosynthesis pathway.

A functional 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway is required for isoprenoid biosynthesis and hence survival in Escherichia coli and most other bacteria. In the first two steps of the pathway, MEP is produced from the central metabolic intermediates pyruvate and glyceraldehyde 3-phosphate via 1-deoxy-D-xylulose 5-phosphate (DXP) by the activity of the enzymes DXP synthase (DXS) and DXP reductoisomerase (DXR). Because the MEP pathway is absent from humans, it was proposed as a promising new target to develop new antibiotics.

Carotenoid biosynthesis in Arabidopsis: a colorful pathway.

Plant carotenoids are a family of pigments that participate in light harvesting and are essential for photoprotection against excess light. Furthermore, they act as precursors for the production of apocarotenoid hormones such as abscisic acid and strigolactones. In this review, we summarize the current knowledge on the genes and enzymes of the carotenoid biosynthetic pathway (which is now almost completely elucidated) and on the regulation of carotenoid biosynthesis at both transcriptional and post-transcriptional levels.

The arbuscular mycorrhizal symbiosis promotes the systemic induction of regulatory defence-related genes in rice leaves and confers resistance to pathogen infection.

Arbuscular mycorrhizal (AM) symbioses are mutualistic associations between soil fungi and most vascular plants. Their association benefits the host plant by improving nutrition, mainly phosphorus nutrition, and by providing increased capability to cope with adverse conditions. In this study, we investigated the transcriptional changes triggered in rice leaves as a result of AM symbiosis, focusing on the relevance of the plant defence response.

Stability of the MON 810 transgene in maize.

We analysed the DNA variability of the transgene insert and its flanking regions in maize MON 810 commercial varieties. Southern analysis demonstrates that breeding, since the initial transformation event more than 10 years ago, has not resulted in any rearrangements. A detailed analysis on the DNA variability at the nucleotide level, using DNA mismatch endonuclease assays, showed the lack of polymorphisms in the transgene insert.

Activation of basal defense mechanisms of rice plants by Glomus intraradices does not affect the arbuscular mycorrhizal symbiosis.

• Arbuscular mycorrhizal (AM) fungi establish symbiotic associations with a wide range of plant species. AM fungi must then have the ability to suppress, neutralize or evade the plant defense response. We investigated the physiological and molecular responses of rice to inoculation with the AM fungus Glomus intraradices, focusing on the relevance of the plant defense response during the symbiotic mycorrhizal interaction.

Supply of precursors for carotenoid biosynthesis in plants.

Carotenoids are isoprenoids of industrial and nutritional interest produced by all photosynthetic organisms, including plants. Too often, the metabolic engineering of plant carotenogenesis has been obstructed by our limited knowledge on how the endogenous pathway interacts with other related metabolic pathways, particularly with those involved in the production of isoprenoid precursors. However, recent discoveries are providing new insights into this field.

Pleiotropic regulatory locus 1 (PRL1) integrates the regulation of sugar responses with isoprenoid metabolism in Arabidopsis.

The biosynthesis of isoprenoids in plant cells occurs from precursors produced in the cytosol by the mevalonate (MVA) pathway and in the plastid by the methylerythritol 4-phosphate (MEP) pathway, but little is known about the mechanisms coordinating both pathways. Evidence of the importance of sugar signaling for such coordination in Arabidopsis thaliana is provided here by the characterization of a mutant showing an increased accumulation of MEP-derived isoprenoid products (chlorophylls and carotenoids) without changes in the levels of relevant MEP pathway transcripts, proteins, or enzyme activities. This mutant was found to be a new loss-of-function allele of PRL1 (Pleiotropic Regulatory Locus 1), a gene encoding a conserved WD-protein that functions as a global regulator of sugar, stress, and hormone responses, in part by inhibition of SNF1-related protein kinases (SnRK1).

Colors in the dark: a model for the regulation of carotenoid biosynthesis in etioplasts.

Carotenoids are plastidial isoprenoid pigments essential for plant life. High carotenoid levels are found in chloroplasts and chromoplasts, but they are also produced in the etioplasts of seedlings that germinate in the dark. Our recent work has shown that an enhanced production of carotenoids in plastids of dark-grown Arabidopsis thaliana seedlings results in an improved transition to photosynthetic development (greening) upon illumination, illustrating the relevance of regulating etioplast carotenoid biosynthesis for plant fitness.

An oligo-based microarray offers novel transcriptomic approaches for the analysis of pathogen resistance and fruit quality traits in melon (Cucumis melo L.).

Background: Melon (Cucumis melo) is a horticultural specie of significant nutritional value, which belongs to the Cucurbitaceae family, whose economic importance is second only to the Solanaceae. Its small genome of approx. 450 Mb coupled to the high genetic diversity has prompted the development of genetic tools in the last decade.

Phytoene synthase activity controls the biosynthesis of carotenoids and the supply of their metabolic precursors in dark-grown Arabidopsis seedlings.

Carotenoids are plastidial isoprenoids essential for plant life. In Arabidopsis thaliana carotenoid biosynthesis is strongly upregulated when seedlings that germinate in the dark (etiolated) emerge from the soil and light derepresses photomorphogenesis, causing etioplasts to become chloroplasts. We found that carotenoid biosynthesis is also induced when deetiolation is derepressed in the absence of actual light, eventually resulting in improved greening (chlorophyll accumulation) upon illumination.

Diurnal oscillation in the accumulation of Arabidopsis microRNAs, miR167, miR168, miR171 and miR398.

MicroRNAs (miRNAs) are small RNAs acting as regulators of eukaryotic gene expression at the post-transcriptional level. Plant miRNAs have been implicated in developmental processes and adaptation to the environment. We show that the accumulation of four Arabidopsis miRNAs (miR171, miR398, miR168 and miR167) oscillates during the diurnal cycle, their accumulation increasing during the light period of the daytime and decreasing in darkness.