Optimisation of regeneration and maintenance of morphogenic callus in pear (Pyrus communis L.) by simple and double regeneration techniques

The purpose of our work was to improve the regeneration capacity of leaf explants and the maintenance of shoot morphogenesis in callus of six pear cultivars: Abate Fetel, Conference, Dar Gazi, Harrow Sweet, Kaiser and Williams, by altering the composition of both regeneration and proliferation media of explant donor shoots, and choosing the right type of explant. Regeneration capacity of leaf explants collected from in vitro shoots has been improved in the majority of cultivars also due to shoot preconditioning. For the first time, long term morphogenic callus production and maintenance have been established in some cultivars by a “double regeneration”. Using this technique, morphogenic callus of two cultivars, ‘Dar Gazi’ and ‘Conference’, was maintained for several subcultures but only when they were initiated from small leaflets – less than 2–3 mm long – which had been collected from the neoformed adventitious buds. MS medium [Murashige, T., Skoog, F., 1962. A revised medium for rapid growth and bioassay with tobacco tissue culture. Physiol. Plant. 15, 473–497] proved to be an efficient regeneration medium by stimulating adventitious buds, while the explants of all cultivars, except for Kaiser, showed a high regeneration capacity when they were collected from shoots proliferated on modified QL medium [Quoirin, M, Lepoivre, P., Boxus, P., 1977. Un premier bilan de dix annees de recherche sur les cultures de meristemes et la multiplication in vitro de fruitiers ligneux. Compte rendu des recherches, Station des Cultures Fruitieres et Maraicheres de Gembloux (1976–1977), 93–117]. This medium conferred leaf expansion, overcoming 90% of regeneration in explants of cv Dar Gazi and Williams. Well expanded leaves were obtained and collected by rooting the shoots, while regeneration percentage was not improved and the number of adventitious shoots was increased in most cultivars, reaching up to 10 shoots per explant. When cefotaxime at 200 mg/l, which is normally effective in controlling Agrobacterium, was used for genetic transformation, regeneration percentage and number of shoots per explant (in leaf explants collected from rooted shoots) were increased and a uniform bud regeneration on all the leaf surface was promoted.L'articolo è disponibile sul sito dell'editore http://www.sciencedirect.co

Olea

The genus Olea contains about 30 species were grouped into three subgenera, Tetrapilus, Paniculatae, and Olea (cultivated olive and wild relatives), found in Asia, Australia and Asia, Africa and Europe, respectively. The species O. europaea L. includes six subspecies: Olea europaea L. ssp. europaea (the Mediterranean olives); O. e. laperrinei (distributed in Saharan massifs of Hoggar, Aïr, Jebel Marra in Algeria); O. e. cuspidata (which moved from South Africa to Egypt, East Australian areas and Hawaii, and from Arabia to northern India and Southwest China); O. e. guanchica (Canary Islands); O. e. maroccana (southwestern Morocco); and O. e. cerasiformis (Madeira). Using molecular markers, it has been ascertained that the Mediterranean olives include the cultivated types (O. europaea L. ssp. europaea var. sativa), the true wild oleaster (O. e. e. var. sylvestris), and the feral form olevaster from seedlings raised from seeds of the cultivated types. The oleaster has a narrow range of distribution and it is often mistaken for olevaster. Recolonization of the Mediterranean basin by Oleaster occurred after the last glacial event, from refuges located in both eastern and western Mediterranean basin areas toward southern Europe. Oleaster is a source of rootstock for propagating new improved cultivated varieties. Cultivated and wild forms have the same diploid chromosome number (2n = 46) and are fully interfertile. Triploid and tetraploid genotypes have been isolated from cultivated O.e.e., but polyploid forms have been found in endangered natural populations of O. e. guancica (tetraploid) and O. e. maroccana (hexaploid). Individual oleaster trees showing superior performance for size and/or oil content of fruit were selected empirically during olive domestication and propagated vegetatively as clones using cuttings that were planted directly or, more recently, grafted onto indigenous oleasters. Genetic markers linked for most important agronomic traits, such as size of the tree, content of secondary products of fruit, flowering induction, oil quality, and biotic and abiotic resistance, will help introgression by conventional breeding of oleaster trait-enhancing genes into cultivated olive. Successful results were difficult to achieve due to both the complex genetic basis of the traits to be improved and the long juvenile period of the progenies that delays the expression of the target traits. In vitro techniques to regenerate doubled haploids from hybrids or somaclonal variation induction may complement classical breeding procedures. Genetic transformation could speed up the development of new genotypes, and transgenic olive plants with modified growth habit and putative induced disease resistance are being tested under filed conditions. However, the development of an efficient regeneration method from mature tissue is the limiting factor for the routine application of this technology to olive genetic improvement.La pubblicazione originale è disponibile sul sito dell'editore http://www.springerlink.co

Phytochrome A as a functional marker of phyletic relationships in Nicotiana genus

Nicotiana is a small and well characterized genus of Solanaceae and in this study we have used polymorphisms in phytochrome A coding sequence (phyA) and promoter to asses the phylogenetic relationships among species representative of all the sections of the genus. Allopolyploid species kept the two copies of the gene derived from each of the progenitors as resulted from the analyses of the coding region and promoter. Moreover, both copies of phyA present in tetraploids are transcribed, indicating that are properly regulated and do not undergo silencing

The Longevity of Fruit Trees in Basilicata (Southern Italy): Implications for Agricultural Biodiversity Conservation

In the Mediterranean basin, agriculture and other forms of human land use have shaped the environment since ancient times. Intensive and extensive agricultural systems managed with a few cultured plant populations of improved varieties are a widespread reality in many Mediterranean countries. Despite this, historical cultural landscapes still exist in interior and less intensively managed rural areas. There, ancient fruit tree varieties have survived modern cultivation systems, preserving a unique genetic heritage. In this study, we mapped and characterized 106 living fruit trees of ancient varieties in the Basilicata region of southern Italy. Tree ages were determined through tree ring measurements and radiocarbon analyses. We uncovered some of the oldest scientifically dated fruit trees in the world. The oldest fruit species were olive (max age 680 +/- 57 years), mulberry (647 +/- 66 years), chestnut (636 +/- 66 years), and pear (467 +/- 89 years). These patriarchs hold a unique genetic resource; their preservation and genetic maintenance through agamic propagation are now promoted by the Lucan Agency for the Development and Innovation in Agriculture (ALSIA). Each tree also represents a hub for biodiversity conservation in agrarian ecosystems: their large architecture and time persistence guarantee ecological niches and micro-habitats suitable for flora and fauna species of conservation significance

Plant microRNAs from Moringa oleifera Regulate Immune Response and HIV Infection

Traditional medicine is often chosen due to its affordability, its familiarity with patient's cultural practices, and its wider access to the local community. Plants play an important role in providing indispensable nutrients, while specific small RNAs can regulate human gene expression in a cross-kingdom manner. The aim of the study was to evaluate the effects of plant-enriched purified extract microRNAs from Moringa oleifera seeds (MO) on the immune response and on HIV infection. Bioinformatic analysis shows that plant microRNAs (p-miRs) from MO belonging to 18 conserved families, including p-miR160h, p-miR166, p-miR482b, p-miR159c, p-miR395d, p-miR2118a, p-miR393a, p-miR167f-3p, and p-miR858b are predicted to target with high affinity BCL2, IL2RA, TNF, and VAV1, all these being involved in the cell cycle, apoptosis, immune response and also in the regulation of HIV pathogenesis. The effects of MO p-miRs transfected into HIV+ PBMCs were analyzed and revealed a decrease in viability associated with an increase of apoptosis; an increase of T helper cells expressing Fas and a decrease of intracellular Bcl2 protein expression. Meanwhile no effects were detected in PBMCs from healthy donors. In CD4(+) T cells, transfection significantly reduced cell activation and modified the T cell differentiation, thereby decreasing both central and effector memory cells while increasing terminal effector memory cells. Interestingly, the p-miRs transfection induces a reduction of intracellular HIV p24 protein and a reduction of viral DNA integration. Finally, we evaluated the effect of synthetic (mimic) p-miR858b whose sequence is present in the MO p-miR pool and predicted to target VAV1, a protein involved in HIV-Nef binding. This protein plays a pivotal role in T cell antigen receptor (TCR) signaling, so triggering the activation of various pathways. The transfection of HIV+ PBMCs with the synthetic p-miR858b showed a reduced expression of VAV1 and HIV p24 proteins. Overall, our evidence defines putative mechanisms underlying a supplementary benefit of traditional medicine, alongside current antiretroviral therapy, in managing HIV infection in resource-limited settings where MO remains widely available

Monochromic Radiations Provided by Light Emitted Diode (LED) Modulate Infection and Defense Response to Fire Blight in Pear Trees

open access articlePathogenesis-related (PR) proteins are part of the systemic signaling network that perceives pathogens and activates defenses in the plant. Eukaryotic and bacterial species have a 24-h ‘body clock’ known as the circadian rhythm. This rhythm regulates an organism’s life, modulating the activity of the phytochromes (phys) and cryptochromes (crys) and the accumulation of the corresponding mRNAs, which results in the synchronization of the internal clock and works as zeitgeber molecules. Salicylic acid accumulation is also under light control and upregulates the PR genes expression, increasing plants’ resistance to pathogens. Erwinia amylovora causes fire blight disease in pear trees. In this work, four bacterial transcripts (erw1-4), expressed in asymptomatic E. amylovora-infected pear plantlets, were isolated. The research aimed to understand how the circadian clock, light quality, and related photoreceptors regulate PR and erw genes expression using transgenic pear lines overexpressing PHYB and CRY1 as a model system. Plantlets were exposed to different circadian conditions, and continuous monochromic radiations (Blue, Red, and Far-Red) were provided by light-emitting diodes (LED). Results showed a circadian oscillation of PR10 gene expression, while PR1 was expressed without clear evidence of circadian regulation. Bacterial growth was regulated by monochromatic light: the growth of bacteria exposed to Far-Red did not differ from that detected in darkness; instead, it was mildly stimulated under Red, while it was significantly inhibited under Blue. In this regulatory framework, the active form of phytochrome enhances the expression of PR1 five to 15 fold. An ultradian rhythm was observed fitting the zeitgeber role played by CRY1. These results also highlight a regulating role of photoreceptors on the expression of PRs genes in non-infected and infected plantlets, which influenced the expression of erw genes. Data are discussed concerning the regulatory role of photoreceptors during photoperiod and pathogen attacks