Deep Sequencing Analysis of RNAs from Citrus Plants Grown in a Citrus Sudden Death-Affected Area Reveals Diverse Known and Putative Novel Viruses.

Citrus sudden death (CSD) has caused the death of approximately four million orange trees in a very important citrus region in Brazil. Although its etiology is still not completely clear, symptoms and distribution of affected plants indicate a viral disease. In a search for viruses associated with CSD, we have performed a comparative high-throughput sequencing analysis of the transcriptome and small RNAs from CSD-symptomatic and -asymptomatic plants using the Illumina platform. The data revealed mixed infections that included Citrus tristeza virus (CTV) as the most predominant virus, followed by the Citrus sudden death-associated virus (CSDaV), Citrus endogenous pararetrovirus (CitPRV) and two putative novel viruses tentatively named Citrus jingmen-like virus (CJLV), and Citrus virga-like virus (CVLV). The deep sequencing analyses were sensitive enough to differentiate two genotypes of both viruses previously associated with CSD-affected plants: CTV and CSDaV. Our data also showed a putative association of the CSD-symptomatic plants with a specific CSDaV genotype and a likely association with CitPRV as well, whereas the two putative novel viruses showed to be more associated with CSD-asymptomatic plants. This is the first high-throughput sequencing-based study of the viral sequences present in CSD-affected citrus plants, and generated valuable information for further CSD studies

Multiple origins of the common chameleon in southern Italy

The common chameleon Chamaeleo chamaeleon is a Mediterranean lizard which has been introduced in many islands and its native origin in European countries is debated. Chameleons have been introduced in southern Italy, possibly from the Middle East and Tunisia. We conducted genetic analyses on mitochondrial DNA 16S gene on a larger sample. We observed a multiple origin for the Salento (Apulia, southern Italy) population, with individuals phylogenetically related to populations of North Africa and two areas in the Middle East. Some individuals may have been released before the 1950s and some others in the 1980s, improving the establishment success of this species

NPBTs FOR SUSTAINABLE VITICULTURE MANAGEMENT TO BIOTIC AND ABIOTIC STRESS

New plant breeding techniques (NPBTs) aim to overcome traditional breeding limits for plant improvement to biotic and abiotic stresses satisfying the European Policies requirements that promote chemical input reduction and a more sustainable agriculture. We decided to apply genome editing (via CRISPR/Cas9) focusing on susceptibility genes to control powdery mildew: we chosen to knock-out two genes belonging to MLO (Mildew Locus O) family: VvMLO7 and VvMLO6. The same approach was used to cope with abiotic stresses, in specifc drought, performing a knock-out of four genes, two belonging to GST (Glutathione S-Transferase) and two to PME (Pectin Methyl Esterase) gene families. In parallel to genome editing, we also applied cisgenesis to move the resistance locus RPV3-1 (Resistance to Plasmopara viticola) into economically important cultivars. This locus is formed by two di\ufb00erent genes that were inserted individually and in combination to evaluate their e\ufb00ects. One of the drawbacks linked to classical Agrobacterium tumefaciens mediated transformation is the insertion of unrelated transgene (e.g., antibiotic resistance). These markers are required for transgenic plants selection, but undesirable to be retained in commercial plants due to possible toxicity or allergenicity to humans and animals, in addition to their potential hazards for the environment. To overcome these limits, we exploit an inducible excision system based on a Cre-lox recombinase technology controlled by a heat-shock inducible promoter that will be activated once the transformation event(s) will be confrmed. Embryogenic calli of Chardonnay, Glera, Microvine, Pinot Noir, Sangiovese, were used in stable transformation with A. tumefaciens carrying the genome editing construct with the MLO-guideRNAs and the cisgenic construct carrying the two RPV3-1 genes. Embryogenic calli of rootstocks 110 Richter and SO4 were transformed with genome editing construct carrying GST and PME guideRNAs in two independent transformations. Regenerated embryos from all the transformation events are now under evaluation

New plant breeding technologies towards a more sustainable viticulture

European grapevine cultivars are highly susceptible to many pathogens that are managed through large pesticide use. Nevertheless, the European policies promote pesticide use reduction and new environmentally friendly methods for a more sustainable agriculture. In this framework, grapevine genetic improvement could benefit from New Plant Breeding Technologies. In order to reduce fungal susceptibility, we will produce knock-out plants from embryogenic calli using CRISPR/Cas9 technology. Studies in barley reported the acquisition of powdery mildew resistance by knocking out susceptibility genes belonging to the MLO (Mildew Locus O) family. In this study, our approach takes advantage from CRISPR/Cas9 technology to perform a multiple knockout of MLO genes. Among the 17 VvMLOs reported in grapevine we designed constructs to target VvMLO6 and VvMLO7. Golden Gate assembly was used to produce three different constructs (containing two guideRNAs for each gene) to knocking-out the targets singularly or by producing a double mutant. Usually, the genetic engineering techniques, mediated by A. tumefaciens, involve the insertion of exogenous selectable marker genes. These markers are required for selection of transgenic plants, but they are undesirable to be retained in commercial transgenic plants due to possible toxicity or allergenicity to humans and potential environmental hazard. To overcome these limits, we opted for a \u201cclean\u201d editing strategy developing an inducible excision system. This approach is based on a recombinase technology involving the Cre-loxP system from the P1 bacteriophage under a heat-shock inducible promoter to be activated once the editing event(s) will be confirmed. Obtainment of embryogenic calli is one of the main bottlenecks for application of CRISPR/Cas9: for two seasons, we collected inflorescences from Chardonnay, Glera, Microvine, Pinot Noir, Sangiovese cultivars and two rootstocks, 110 Richter and SO4, cultured and maintained in vitro up to embryo development and then used to perform Agrobacterium tumefaciens GV3101 mediated transformation

Chitosan nanocarriers-mediated delivery of double-stranded RNA "in planta"

Agriculture is currently facing numerous challenges: the rapid rise of the world population, the consequent growth in food demand, the global decrease in crop yield. Particularly regarding the last issue, climate change is worsening the environmental stresses that commonly affect crops, and the use of resources – such as fertilizers and pesticides – is highly inefficient and pollutant. In this context, research is looking for new approaches to improve crop productivity by more efficient and environmentally friendly practices. It has been shown that nanomaterials are suitable for the development of cutting-edge technologies with the aim of improving the delivery of bioactive substances on plants and to promote their resistance to biotic and abiotic stresses. Among organic polymers, chitosan, if used in the nanoscale form, shows both properties; it can induce biological responses concerning plant defense against diseases and pathogen attack, and it is particularly suitable as a carrier for several molecules. Another innovative method for the defense of crops is the exploitation of the spray-induced gene silencing (SIGS) based on the activation of the so-called RNA-interference (RNAi). It involves exogenous double stranded RNAs (dsRNAs) targeting an essential pathogen gene, which trigger the RNAi pathway leading to the translational repression by degradation of target homologous mRNAs. In our case, the research aimed to verify the feasibility of dsRNA distribution on plant surface by means of functionalized chitosan nanoparticles (CH-NPs), thus allowing the protection of the doping agent and its efficient delivery. Here we show the preliminary results regarding the characterization of CH-NPs, their loading with dsRNAs and their interaction with the leaf surface of Nicotiana benthamiana plants. The effects of the dose-dependent distribution were analyzed by confocal microscopy upon incorporation of a fluorescent probe