No abstract

Citrus is the most important fruit tree crop in the world, with a production of more than 100 million tons annually. The area of origin of Citrus is believed to be southeastern Asia, where its domestication started. It has become clear that only citron, mandarin, and pummelo are true species within genus Citrus, being other important Citrus types, as sweet orange, sour orange, lemon, lime, grapefruit and other mandarins originated from hybridization between these ancestral species. In spite of the many efforts put in classical breeding programs in the last 100 years, current citrus industry relies on various groups of varieties that are grafted onto rootstocks adapted to different abiotic and biotic stresses. Most of these genotypes have been generated by chance, mostly as budsports but also as natural hybrids or seedlings selected by men in the wild or in orchards. Citrus breeding is complicated due to its complex reproductive biology. In this context, genetic transformation offers an important alternative for the genetic improvement of citrus. Moreover, it is probably the most efficient approach to make reverse genetics in citrus to investigate gene function and thus to gain better understanding in metabolic processes and plant‐pathogen‐environment interactions.

No abstract

An assay to identify interactions between Citrus dwarfing viroid (CDVd) and Citrus tristeza virus (CTV) showed that viroid titer was enhanced by the coinfecting CTV in Mexican lime but not in etrog citron. Since CTV encodes three RNA silencing suppressors (RSSs), p23, p20 and p25, an assay using transgenic Mexican limes expressing each RSS revealed that p23 and, to a lesser extent, p25 recapitulated the effect observed with coinfections of CTV and CDVd. V iroids are infectious, unencapsidated, single-stranded, and highly structured noncoding circular RNAs of 250 to 400 nucleotides (nt). Despite their simplicity, viroids interact with cell factors, which redirect them to replicate and traffic throughout the plant while avoiding the RNA silencing machinery they trigger in their hosts (1).Indexing tests have shown that viroids are widespread in commercial citrus orchards, wherein trees may be coinfected with other graft-transmissible pathogens. Data regarding virus-viroid interactions are very scarce, but the information available indicates that such interactions may alter symptom expression (2, 3). Since coinfection of citrus species with Citrus tristeza virus (CTV) and viroids is not rare, assays were conducted to establish whether interactions between these two types of pathogens actually exist.The assays were performed by comparing single and double infections of the two pathogens in etrog citron (Citrus medica L.) (viroid bioindicator) and Mexican lime (Citrus aurantifolia [Christm.] Swingle) (CTV bioindicator). Citrus dwarfing viroid (CDVd) (GenBank accession number EU934004), inducing moderate but specific symptoms in etrog citron (4), and CTV (T-305 strain), inducing symptoms in Mexican lime (5), were chosen for this study. To synchronize infection, Volkamer lemon (Citrus volkameriana Ten. & Pasq.) seedlings were graft inoculated with CDVd and/or CTV before being used as rootstocks. Etrog citron and Mexican lime were graft propagated to produce groups of five plants for each of the following treatments: (i) plants singly infected with CDVd, (ii) plants singly infected with CTV, (iii) plants coinfected with CTV and CDVd, and (iv) noninfected controls. CTV and CDVd infection was assessed by immunoprinting enzyme-linked immunosorbent assay (ELISA) (6) and dot blot hybridization (7), respectively.After an incubation period of 4 months at 25°C, plant height was measured (Fig. 1) and data were subjected to multifactor analysis of variance (ANOVA). The results indicated that etrog citron singly infected with CTV (P value, 0.00001) or CDVd (P value, 0.05) was stunted, as was Mexican lime singly infected with CTV (P value, 0.0013) but not that with CDVd (P value, 0.98). Height reduction in coinfected plants resulted from the added effect of each pathogen, indicating no interaction between CDVd and CTV in either host (interaction P value for etrog citron, 0.29; interaction P value for Mexican lime, 0.44). Similarly, symptom expression in stems and leaves resulted from the added effect of each pathogen, revealing agai...

CIGB-230, a mixture of a DNA plasmid expressing hepatitis C virus (HCV) structural antigens and a HCV recombinant capsid protein, has demonstrated to elicit strong immune responses in animals. The present study evaluated the plasmid biodistribution after the administration of CIGB-230 in mice, as well as toxicity of this vaccine candidate in rats. In the biodistribution study, mice received single or repeated intramuscular injections of CIGB-230, 50 μg of plasmid DNA mixed with 5 μg of Co.120 protein. Plasmid presence was assessed in ovaries, kidney, liver, pancreas, mesenteric ganglion, blood, and muscle of the injection site by a qualitative polymerase chain reaction. The toxicology evaluation included treatment groups receiving doses 5, 15, or 50 times higher, according to the body weight, than the expected therapeutic clinical dose. During the first hour after repeated inoculation, a promiscuous distribution was observed. However, 3 months later, plasmid could not be detected in any tissue. There was an absence of detectable adverse effects on key toxicology parameters and no damage evidenced in inspected organs and tissues. These results indicate that CIGB-230 is nontoxic at local and systemic levels and no concerns about persistence are observed, which support clinical testing of this vaccine candidate against HCV.

No abstract

No abstract