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Apricot (Prunus armeniaca L.) is a cosmopolitan, major stone fruit species cultivated for its delicious drupes. Strong concerns about loss of diversity in apricot have been recently put forward mainly because of the enduring transition from local to globalized varieties more suitable for intensive agriculture. Italy, one of the top producing countries in the world, has arguably one of the richest apricot germplasms, with the Campania region being a traditional and leading area of cultivation since Roman times. This work aimed to study the molecular diversity of an ex-situ collection of local apricot varieties. They once flourished in conventional cropping systems, but are nowadays neglected, surviving in family farms, and sold only in local markets. We investigated the level of genetic and genotypic diversity, assessed clonality in the population, and verified the presence of genetic structure and differentiation in 73 apricot varieties by using fluorescent SSR markers resolved in capillary electrophoresis (SSR-CE). The analysis indicated a high level of genetic diversity (with little locus-specific differences) and of genotypic assortment, with few possible synonyms. Moreover, the investigation of relatedness among apricot landraces and the negligible within-landraces differentiation are consistent with a common origin of the germplasm, a likely result of an adaptive diversification that is mainly due to similar environmental and agricultural factors. This work highlights the value of the traditional germplasm where crops thrived. Moreover, it provides support for studying the possible mechanisms of evolution and adaptation and for implementing measures for the exploitation, regeneration, and on-farm promotion of the apricot landraces. [ABSTRACT FROM AUTHOR]

Transgenic plants that express double-stranded RNA (dsRNA) targeting vital insect genes have recently emerged as a valuable new tool for pest control. In this study, tobacco plants were transformed to produce dsRNA targeting Sl 102 gene that is involved in the immune response of Spodoptera littoralis larvae, a serious lepidopteran pest of several crops. Experimental larvae reared on transgenic tobacco lines showed (1) a strongly reduced level of Sl 102 transcripts, which was positively associated with food consumption; (2) a substantial impairment of the encapsulation response mediated by hemocytes; and (3) a marked increase in the susceptibility to Xentari™, a Bacillus thuringiensis-based insecticide. Importantly, this approach may allow a reduction in the doses of B. thuringiensis used for field applications and enhance its killing activity on mature larvae. The results obtained thus support the use of immunosuppressive RNAi plants to enhance the performance of microbial insecticides on lepidopteran larvae. [ABSTRACT FROM AUTHOR]

Objectives: To engineer broad spectrum resistance in potato using different expression strategies. Results: The previously identified Ribosome-Inactivating Protein from Phytolacca heterotepala was expressed in potato under a constitutive or a wound-inducible promoter. Leaves and tubers of the plants constitutively expressing the transgene were resistant to Botrytis cinerea and Rhizoctonia solani, respectively. The wound-inducible promoter was useful in driving the expression upon wounding and fungal damage, and conferred resistance to B. cinerea. The observed differences between the expression strategies are discussed considering the benefits and features offered by the two systems. Conclusions: Evidence is provided of the possible impact of promoter sequences to engineer BSR in plants, highlighting that the selection of a suitable expression strategy has to balance specific needs and target species. [ABSTRACT FROM AUTHOR]

Systemin is a tomato peptide hormone that promotes plant defense against plant-chewing pests. This octadecapeptide is released from the C-terminal region of prosystemin, a 200 amino acid-long cytosolic precursor. Homologues of the tomato prosystemin are present in other Solanaceae but not in tobacco. This species does not respond to the exogenous application of the tomato systemin. Previously, it was shown that the expression of the full-length tomato prosystemin cDNA in tobacco affects the proteomic repertoire and increases plant tolerance against phytopathogenic fungi. In this work, to evaluate the relevance of the systemin sequence, we generated transgenic tobacco plants that express a mutated prosystemin lacking the systemin region. By using proteomics and gene expression analyses, we show that the constitutive expression of the truncated prosystemin altered the proteomic profile of tobacco leaves and increased plant resistance against B. cinerea. The overlap of the modifications caused by the expression of the full-length and the truncated prosystemin indicated that these alterations occur also in the absence of the systemin sequence. Although the cellular mechanisms of prosystemin cleavage are elusive, our work demonstrates that the expression of a heterologous cytosolic peptide-hormone precursor, irrespective of the presence of its peptide domain, associated with unpredicted changes at the proteomic and transcriptional level. [ABSTRACT FROM AUTHOR]

Systemin is a signal peptide that promotes the response to wounding and herbivore attack in tomato. This 18-amino acid peptide is released from a larger precursor, prosystemin. To study the role of systemin as a modulator of defense signaling, we generated tomato ( Solanum lycopersicum) transgenic plants that overexpress the prosystemin cDNA. We carried out a transcriptomic analysis comparing two different transgenic events with the untransformed control. The Gene Ontology categories of the 503 differentially expressed genes indicated that several biological functions were affected. Systemin promotes the expression of an array of defense genes that are dependent on different signaling pathways and it downregulates genes connected with carbon fixation and carbohydrate metabolism. These alterations present a degree of overlap with the response programs that are classically associated to pathogen defense or abiotic stress protection, implying that end products of the systemin signaling pathway may be more diverse than expected. We show also that the observed transcriptional modifications have a relevant functional outcome, since transgenic lines were more resistant against very different biotic stressors such as aphids ( Macrosiphum euphorbiae), phytopathogenic fungi ( Botrytis cinerea and Alternaria alternata) and phytophagous larvae ( Spodoptera littoralis). Our work demonstrated that in tomato the modulation of a single gene is sufficient to provide a wide resistance against stress by boosting endogenous defense pathways. Overall, the data provided evidence that the systemin peptide might serve as DAMP signal in tomato, acting as a broad indicator of tissue integrity. [ABSTRACT FROM AUTHOR]

Italy and Spain are the countries with the oldest record of tomato cultivation in Europe and arguably, with the higher number of traditional and heirloom varieties. In this work we evaluated the genetic diversity and structure in a sample of 26 cultivated accessions belonging to four traditional tomato types, Muchamiel and De la Pera from Spain, and San Marzano and Sorrento from Italy. The (GATA) fingerprinting of the 109 genotypes confirmed the ability of this DNA marker to discriminate tomato plants that are otherwise difficult to distinguish. Furthermore, both the estimated population structure and the genetic differentiation statistics were consistent in indicating that subpopulations are more likely to correspond to farmers' breeding efforts and market specialization than to country-specific groups. Our results provide useful information not only for germplasm description and management but also for current breeding programs in both regions. [ABSTRACT FROM AUTHOR]

An evaluation of the potential allergenicity of different tomato ecotypes is reported. Twelve tomato ecotypes were assessed through a proteomic approach, using pools of sera of allergic patients from two different regions (Emilia Romagna in Northern Italy and Campania in Southern Italy), in order to identify the major allergens and evaluate differences in IgE binding properties of the tomato cultivars. Pooled sera of allergic people from Emilia Romagna showed as the main allergen a suberization-associated anionic peroxidase, whereas pooled sera of allergic patients from Campania were mostly reactive to profilin. The two proteins were identified through a proteomic approach based on the use of high-resolution mass spectrometric techniques. Quite interestingly, in some cases, several ecotypes showed a less reactivity toward patients' sera than other, potentially indicating the possibility to identify ipoallergenic varieties. Anyway, the allergenic pattern response to tomatoes was serum-specific, indicating that the allergenic properties of different tomato ecotypes are defined by the specific proteins to which the patient is sensitized, a strong indication that ipoallergenicity of the different ecotypes is possible, but mostly related to the individual susceptibility. [ABSTRACT FROM AUTHOR]

Short peptides can be expressed in plants using synthetic genes encoding multiple copies of the peptide spaced by dibasic endoproteolytic cleavage sites. A synthetic gene encoding an array of repeated copies of proctolin, a very well characterized insect myotropic peptide, spaced by Arg residues, was synthesized and expressed in tobacco plants. The successful production of bioactive proctolin from the precursor in transgenic plants was demonstrated by immunoblot, HPLC, mass spectrometry and a bioassay based on the contraction of isolated cockroach hindgut. These results suggest thatin planta, as in animals and yeasts, endopeptidases of the serine proteases family may be involved in precursor processing. [ABSTRACT FROM AUTHOR]