Coupled transcript and metabolite identification: insights on induction and synthesis of resveratrol in peanut, wild relatives and synthetic allotetraploid.

Resveratrol is an antioxidant that is a promising antitumoral, cardioprotective and neuroprotective agent. It has been found in a restricted number of plants including peanut (Arachis hypogaea L.) and its wild relatives. The objective of this study was to understand the relationship between resveratrol content and the expression of putative resveratrol synthase genes in four Arachis genotypes. Two diploids and two tetraploid were analyzed. Contents of resveratrol on non- and UV-treated leaves were estimated using HPLC. Resveratrol synthase (RS) was analyzed using RT-qPCR with primers developed in this study. Sequences of six Arachis species were amplified using two degenerated primer pairs that were designed based on Arachis and general RS available at GenBank. Those sequences were used to qPCR primers design. Test and control leaves were collected from plants cultivated in greenhouse and three biological replicates were evaluated for each genotype. The synthesis of resveratrol in leaves was induced by treatment with UV for 2.5 h. All genotypes studied synthesized resveratrol. Concentrations ranged from 193.66 µg/g in synthetic allotetraploid to 371.97 µg/g in A. duranensis. Natural and induced allotetraoploids showed lower levels of resveratrol than their diploid parents. Untreated samples did not produce significant amounts of resveratrol. The analysis of resveratrol content and levels of RS mRNA allowed the identification of one gene induced by the UV treatment. The data showed different amounts of RS in the different genotypes suggesting early and late response to the UV induction in the different species. The understanding of the variation found among species will help to identify species that have high resveratrol content and their ideal pos-induction times. This also will allow analysis of other tissues where high levels resveratrol would be very important, such as in seeds.

New hybrids from peanut (Arachis hypogaea L.) and synthetic amphidiploid crosses show promise in increasing pest and disease tolerance.

The primary gene pool of the cultivated peanut (Arachis hypogaea L., allotetraploid AABB) is very narrow for some important characteristics, such as resistance to pests and diseases. However, the Arachis wild diploid species, particularly those from the section Arachis, still have these characteristics. To improve peanut crops, genes from the wild species can be introgressed by backcrossing the hybrids with A. hypogaea. When diploid species whose genomes are similar to those of the cultivated peanut are crossed, sterile hybrids result. Artificially doubling the number of chromosomes of these hybrids results in fertile synthetic polyploids. The objectives of this study were: 1) to obtain progenies by crossing amphidiploids with the cultivated peanut, and 2) to characterize these two groups of materials (amphidiploids and progenies) so that they may be efficiently conserved and used. Using morphological, molecular, and pollen viability descriptors we evaluated one cultivar of A. hypogaea (IAC 503), eight synthetic amphidiploids, and the progenies resulting from four distinct combinations of crossing between IAC 503 and four amphidiploids.

A modified acidic approach for DNA extraction from plant species containing high levels of secondary metabolites.

Purified genomic DNA can be difficult to obtain from some plant species because of the presence of impurities such as polysaccharides, which are often co-extracted with DNA. In this study, we developed a fast, simple, and low-cost protocol for extracting DNA from plants containing high levels of secondary metabolites. This protocol does not require the use of volatile toxic reagents such as mercaptoethanol, chloroform, or phenol and allows the extraction of high-quality DNA from wild and cultivated tropical species.

Development and characterization of microsatellite markers for Lychnophora pinaster: a study for the conservation of a native medicinal plant.

Lychnophora pinaster Mart. (Asteraceae) is a Brazilian medicinal plant, extensively employed in popular medicine as an anti-inflammatory, analgesic and healing agent. Thirteen polymorphic microsatellite markers were developed and optimized for L. pinaster from an enriched genomic library. The markers were used to analyse 37 plants from two native populations, generating an average number of 6.6 alleles per polymorphic locus. These loci are important tools for future studies of population genetics.

Isolation and characterization of microsatellite markers for Casearia sylvestris Sw. (Salicaceae), a neotropical medicinal tree.

Casearia sylvestris Sw. is a widespread neotropical tree utilized in popular medicine. Recent research ranked Casearia as one of the most promising genus in the search of drugs against cancer. Despite its wide distribution and pharmacological importance, no microsatellite markers have yet been developed for this genus. In this study, we provide 10 polymorphic microsatellite loci specifically designed for C. sylvestris, used to analyse 90 individuals distributed in two populations from São Paulo state, Brazil. On average, 12.3 alleles per locus were identified, showing the ability of the markers to detect microsatellite polymorphism in this species.

A microsatellite-based, gene-rich linkage map for the AA genome of Arachis (Fabaceae).

Cultivated peanut (Arachis hypogaea) is an important crop, widely grown in tropical and subtropical regions of the world. It is highly susceptible to several biotic and abiotic stresses to which wild species are resistant. As a first step towards the introgression of these resistance genes into cultivated peanut, a linkage map based on microsatellite markers was constructed, using an F(2) population obtained from a cross between two diploid wild species with AA genome (A. duranensis and A. stenosperma). A total of 271 new microsatellite markers were developed in the present study from SSR-enriched genomic libraries, expressed sequence tags (ESTs), and by "data-mining" sequences available in GenBank. Of these, 66 were polymorphic for cultivated peanut. The 271 new markers plus another 162 published for peanut were screened against both progenitors and 204 of these (47.1%) were polymorphic, with 170 codominant and 34 dominant markers. The 80 codominant markers segregating 1:2:1 (P<0.05) were initially used to establish the linkage groups. Distorted and dominant markers were subsequently included in the map. The resulting linkage map consists of 11 linkage groups covering 1,230.89 cM of total map distance, with an average distance of 7.24 cM between markers. This is the first microsatellite-based map published for Arachis, and the first map based on sequences that are all currently publicly available. Because most markers used were derived from ESTs and genomic libraries made using methylation-sensitive restriction enzymes, about one-third of the mapped markers are genic. Linkage group ordering is being validated in other mapping populations, with the aim of constructing a transferable reference map for Arachis.