Diversity of citron (Citrus medica) and phylogenetic analysis of related citron hybrids using molecular markers and essential oil composition

Citrus diversity is known to be essentially supported by three essential basic species, mandarin, pummelo and citron, which are at the origin of quite all the cultivated citrus. Based on studies of phenotype, the citron group (Citrus medica) is supposedly low in genetic diversity compared to mandarins and pummelos. To assess the diversity of the citron group we analyzed the molecular polymorphism of nuclear and cytoplasmic genetic markers and the variation in composition of essential oils from leaves and peels of 24 varieties of citron or apparent hybrids of citron. Our results demonstrate that the citron group has a relatively high allelic diversity, probably due to multiple introductions of different varieties. Self-fertilization was the mode of reproduction which most frequently led to the development of commercial varieties with specific aromas and flavors, such as the cultivar 'Corsican', a putative 'Common Poncire' self-crossed hybrid. However, some varieties appeared to be interspecific hybrids related to citron but only by the male parent. This varietal diversity was probably favored by spreading seeds to extend the cultivation of citron in Mediterranean countries. The chemical diversity does not always correspond to genetic diversity but nevertheless reveals specific profiles associated with some genotypes. (Résumé d'auteur

Higher COVID-19 pneumonia risk associated with anti-IFN-α than with anti-IFN-ω auto-Abs in children

We found that 19 (10.4%) of 183 unvaccinated children hospitalized for COVID-19 pneumonia had autoantibodies (auto-Abs) neutralizing type I IFNs (IFN-alpha 2 in 10 patients: IFN-alpha 2 only in three, IFN-alpha 2 plus IFN-omega in five, and IFN-alpha 2, IFN-omega plus IFN-beta in two; IFN-omega only in nine patients). Seven children (3.8%) had Abs neutralizing at least 10 ng/ml of one IFN, whereas the other 12 (6.6%) had Abs neutralizing only 100 pg/ml. The auto-Abs neutralized both unglycosylated and glycosylated IFNs. We also detected auto-Abs neutralizing 100 pg/ml IFN-alpha 2 in 4 of 2,267 uninfected children (0.2%) and auto-Abs neutralizing IFN-omega in 45 children (2%). The odds ratios (ORs) for life-threatening COVID-19 pneumonia were, therefore, higher for auto-Abs neutralizing IFN-alpha 2 only (OR [95% CI] = 67.6 [5.7-9,196.6]) than for auto-Abs neutralizing IFN-. only (OR [95% CI] = 2.6 [1.2-5.3]). ORs were also higher for auto-Abs neutralizing high concentrations (OR [95% CI] = 12.9 [4.6-35.9]) than for those neutralizing low concentrations (OR [95% CI] = 5.5 [3.1-9.6]) of IFN-omega and/or IFN-alpha 2

Development of a seed cryobank to preserve the citrus genetic resources of INRAE-Cirad germplasm: a complementary strategy to the tree field conservation

International audienceIn genebanks, fruit trees are often maintained as grafted scions on rootstocks in field or greenhouse settings and are therefore exposed to various risks of decay. To guarantee a secure long-term conservation, cryopreservation in liquid nitrogen is currently developed for many plant species. The success of seed freezing depends on their ability to tolerate cold and desiccation. Citrus seeds are described as semi-orthodox because they are partially tolerant to desiccation. Seeds of many citrus are polyembryonic and thus offer the possibility of clonal propagation by seedling. A seed cryopreservation program for polyembryonic varieties of the INRAE-Cirad citrus collection has been initiated. We present here the protocol and the adaptations for varieties sensitive to desiccation. The control of the water content of the seeds is ensured by incubation in atmospheres with controlled relative humidity to eliminate intracellular free water lethal to the cells during freezing. The temperature and duration of incubation during this desiccation step are factors that have a role in maintaining germination capacity. Genetics also has a strong influence on the success of cryopreservation operations. Citrus related to citron (Citrus medica) such as lemons and limes are much more tolerant of low water content than varieties related to mandarin (C. reticulata) such as sweet and sour oranges. Seeds of Fortunella and Poncirus trifoliata and some of their hybrids are unsuitable for cryopreservation because they are too sensitive to moisture content decrease. Apex cryopreservation could be an alternative for these non-orthodox citrus trees. However, regeneration by sowing of frozen seeds is simpler than regeneration of apexes that need to be micrografted to develop a plant. Although improvements to the protocol are still needed to increase germination rates of some varieties, we estimate that we are able to cryopreserve in seed form about half of the citrus collection (~ 500 accessions)

Comparative analysis of citrus seed conservation and germination between diploid and tetraploid rootstocks

Citrus rootstocks are polyembryonic and are thus propagated by seeds. Seeds are extracted at fruit maturity, partially desiccated and stored at low temperature (around 5°C) until use or diffusion. However, during this period, seeds performance regarding germination in terms of delay and percentage varies with the genotypes. The genetic homogeneity in seedlings is also a critical point for the clonal propagation depending on the zygotic embryo germination and to the chromosome doubling that may occur in nucellar embryos. Double diploid (4x) genotypes are considered to confer better tolerance to environmental constraints. The seed quality and seedling homogeneity of five pairs of diploid (2x) and 4x rootstock cultivars were investigated. Seed quality was evaluated by 7 criteria of embryonic rate and of sowing description (speed and duration of germination, number of germinated plants by seed, etc.). The genetic homogeneity was tested by analyzing the ploidy level by flow cytometer and the genetic constitution by SNP and SSR markers. According to the vigor, the delay and the duration of germination, Volka-meriana and citrumelo 1452 were the best genotypes. The ploidy rate did not impact the seed performance but modified the homogeneity of seedlings. Although the ploidy level was more stable in 4x seedlings, the percentage of zygotic plantlets was increased by tetraploidy. The degree of heterogeneity of seedlings may reach 50% in some 4x rootstock cultivars challenging their use by nurserymen. (Texte intégral

Somatic hybridization between diploid Poncirus and Citrus improves natural chilling and light stress tolerances compared with equivalent doubled-diploid genotypes

International audienceThe genome doubling of the allotetraploid somatic hybrid can confer greater tolerance to cold and light stress than the diploid parents and their respective tetraploid

Antisense oligonucleotide-based drug development for Cystic Fibrosis patients carrying the 3849+10kb C-to-T splicing mutation

AbstractAntisense oligonucleotide (ASO)-based drugs for splicing modulation were recently been approved for various genetic diseases with unmet need. Here we aimed to develop an ASO-based splicing modulation therapy for Cystic Fibrosis (CF) patients carrying the 3849+10kb C-to-T splicing mutation in the CFTR gene. We have screened, in FRT cells expressing this mutation, ~30 ASOs chemically modified with 2′-O-Methyl on a phosphrothioate backbone, targeted to prevent the recognition and inclusion of a cryptic exon generated due to the mutation. The screening identified five ASO candidates able to promote CFTR correct splicing and rescue channel activity. Further analyses in well differentiated primary human nasal and bronchial epithelial cells (HNEs, HBEs), derived from patients carrying at least one 3849+10kb C-to-T allele, led to the identification of a highly potent lead ASO. The ASO was efficiently delivered by free uptake into patients’ HNEs and HBEs and completely restored CFTR function to wild type levels in cells from a homozygous patient and led to 43±8% of wild type levels in cells from various heterozygous patients. Optimized efficiency was further obtained with 2’-Methoxy Ethyl chemical modification. The results demonstrate the therapeutic potential and clinical benefit of ASO-based splicing modulation for genetic diseases caused by splicing mutations.</jats:p

Citrus Fruits in historical France: written sources, iconographic and plant remains

International audienc