Genomics of the origin and evolution of CitrusGuohong albert Wu 1 , Javier Terol 2 , Victoria ibanez 2 , antonio López-García 2 , estela Pérez-román 2 , carles borredá 2 , concha Domingo 2 , francisco r. Tadeo 2 , Jose carbonell-caballero 3 , roberto alonso 3 , franck curk 4 , Dongliang Du 5 , Patrick Ollitrault 6 , Mikeal L. roose 7 , Joaquin Dopazo 3,8 , frederick G. Gmitter Jr 5 , Daniel S. rokhsar 1,9,10 & Manuel Talon 2The genus Citrus and related genera (Fortunella, Poncirus, Eremocitrus and Microcitrus) belong to the angiosperm subfamily Aurantioideae of the Rutaceae family, which is widely distributed across the monsoon region from west Pakistan to north-central China and south through the East Indian Archipelago to New Guinea and the Bismarck Archipelago, northeastern Australia, New Caledonia, Melanesia and the western Polynesian islands 1 . Native habitats of citrus and related genera roughly extend throughout this broad area (Extended Data Fig. 1a and Supplementary Table 1), although the geogra phical origin, timing and dispersal of citrus species across southeast Asia remain unclear. A major obstacle to resolving these uncertainties is our poor understanding of the genealogy of complex admixture in cultivated citrus, as has recently been shown 2 . Some citrus are clonally propagated apomictically 3 through nucellar embryony, that is, the development of non-sexual embryos originating in the maternal nucellar tissue of the ovule, and this natural process may have been co-opted during domestication; grafting is a relatively recent phenomenon 4 . Both modes of clonal propagation have led to the domestication of fixed (desirable) genotypes, including interspecific hybrids, such as oranges, limes, lemons, grapefruits and other types.Under this scenario, it is not surprising that the current chaotic citrus taxonomy-based on long-standing, conflicting proposals 5,6 -requires a solid reformulation consistent with a full understanding of the hybrid and/or admixture nature of cultivated citrus species. Here we analyse genome sequences of diverse citrus to characterize the diversity and evolution of citrus at the species level and identify citrus admixtures and interspecific hybrids. We further examine the network of relatedness among mandarins and sweet orange, as well as the pattern of the introgression of pummelos among mandarins for clues to the early stages of citrus domestication. Diversity and evolution of the genus CitrusTo investigate the genetic diversity and evolutionary history of citrus, we analysed the genomes of 58 citrus accessions and two outgroup genera (Poncirus and Severinia) that were sequenced to high coverage, including recently published sequences 2,3,7 as well as 30 new genome sequences described here. For our purpose, we do not include accessions related by somatic mutations. These sequences represent a diverse sampling of citrus species, their admixtures and hybrids (Supplementary Tables 2, 3 and Supplementary Notes 1, 2). Our collection includes accessions from eight previously unsequ...

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The ocular surface of the white domestic pig (Sus scrofa domestica) is used as a helpful model of the human ocular surface; however, a complete histological description has yet to be published. In this work, we studied porcine eyeballs with intact eyelids to describe and characterize the different structures that form the ocular surface, including the cornea and conjunctiva that covers the bulbar sclera, tarsi, and the nictitating membrane. We determined the distribution of goblet cells of different types over the conjunctiva and analyzed the conjunctival-associated lymphoid tissue (CALT). Porcine eyeballs were obtained from a local slaughterhouse, fixed, processed, and embedded in paraffin blocks. Tissue sections (4 μm) were stained with hematoxylin/eosin, Alcian blue/Periodic Acid Schiff, and Giemsa. Slides were also stained with lectins from Arachis hypogaea (PNA) and Helix pomatia (HPA) agglutinins and immunostained with rabbit anti-CD3. We found that the porcine cornea was composed of 6-8 epithelial cell layers, stroma, Descemet's membrane, and an endothelial monolayer. The total corneal thickness was 1131.0±87.5 μm (mean±standard error of the mean) in the center and increased to 1496.9±138.2 μm at the limbus. The goblet cell density was 71.25±12.29 cells/mm, ranging from the highest density (113.04±37.21 cells/mm) in the lower palpebral conjunctiva to the lowest density (12.69±4.29 cells/mm) in the bulbar conjunctiva. The CALT was distributed in the form of intraepithelial lymphocytes and subepithelial diffuse lymphoid tissue. Lenticular-shaped lymphoid follicles, about 8 per histological section, were also present within the conjunctival areas. In conclusion, we demonstrated that the analyzed porcine ocular structures are similar to those of humans, confirming the potential usefulness of pig eyes to study ocular surface physiology and pathophysiology. OPEN ACCESSCitation: Crespo-Moral M, García-Posadas L, López-García A, Diebold Y (2020) Histological and immunohistochemical characterization of the porcine ocular surface. PLoS ONE 15(1): e0227732. https://doi.org/10.