Telomerase RNA gene paralogs in plants - the usual pathway to unusual telomeres.

Telomerase, telomeric DNA and associated proteins together represent a complex, finely tuned and functionally conserved mechanism that ensures genome integrity by protecting and maintaining chromosome ends. Changes in its components can threaten an organism's viability. Nevertheless, molecular innovation in telomere maintenance has occurred multiple times during eukaryote evolution, giving rise to species/taxa with unusual telomeric DNA sequences, telomerase components or telomerase-independent telomere maintenance. The central component of telomere maintenance machinery is telomerase RNA (TR) as it templates telomere DNA synthesis, its mutation can change telomere DNA and disrupt its recognition by telomere proteins, thereby leading to collapse of their end-protective and telomerase recruitment functions. Using a combination of bioinformatic and experimental approaches, we examine a plausible scenario of evolutionary changes in TR underlying telomere transitions. We identified plants harbouring multiple TR paralogs whose template regions could support the synthesis of diverse telomeres. In our hypothesis, formation of unusual telomeres is associated with the occurrence of TR paralogs that can accumulate mutations, and through their functional redundancy, allow for the adaptive evolution of the other telomere components. Experimental analyses of telomeres in the examined plants demonstrate evolutionary telomere transitions corresponding to TR paralogs with diverse template regions.

Fossil berries reveal global radiation of the nightshade family by the early Cenozoic.

Fossil discoveries can transform our understanding of plant diversification over time and space. Recently described fossils in many plant families have pushed their known records farther back in time, pointing to alternative scenarios for their origin and spread. Here, we describe two new Eocene fossil berries of the nightshade family (Solanaceae) from the Esmeraldas Formation in Colombia and the Green River Formation in Colorado (USA). The placement of the fossils was assessed using clustering and parsimony analyses based on 10 discrete and five continuous characters, which were also scored in 291 extant taxa. The Colombian fossil grouped with members of the tomatillo subtribe, and the Coloradan fossil aligned with the chili pepper tribe. Along with two previously reported early Eocene fossils from the tomatillo genus, these findings indicate that Solanaceae were distributed at least from southern South America to northwestern North America by the early Eocene. Together with two other recently discovered Eocene berries, these fossils demonstrate that the diverse berry clade and, in turn, the entire nightshade family, is much older and was much more widespread in the past than previously thought.

Phylogenomic discordance suggests polytomies along the backbone of the large genus Solanum.

PREMISE: Evolutionary studies require solid phylogenetic frameworks, but increased volumes of phylogenomic data have revealed incongruent topologies among gene trees in many organisms both between and within genomes. Some of these incongruences indicate polytomies that may remain impossible to resolve. Here we investigate the degree of gene-tree discordance in Solanum, one of the largest flowering plant genera that includes the cultivated potato, tomato, and eggplant, as well as 24 minor crop plants. METHODS: A densely sampled species-level phylogeny of Solanum is built using unpublished and publicly available Sanger sequences comprising 60% of all accepted species (742 spp.) and nine regions (ITS, waxy, and seven plastid markers). The robustness of this topology is tested by examining a full plastome dataset with 140 species and a nuclear target-capture dataset with 39 species of Solanum (Angiosperms353 probe set). RESULTS: While the taxonomic framework of Solanum remained stable, gene tree conflicts and discordance between phylogenetic trees generated from the target-capture and plastome datasets were observed. The latter correspond to regions with short internodal branches, and network analysis and polytomy tests suggest the backbone is composed of three polytomies found at different evolutionary depths. The strongest area of discordance, near the crown node of Solanum, could potentially represent a hard polytomy. CONCLUSIONS: We argue that incomplete lineage sorting due to rapid diversification is the most likely cause for these polytomies, and that embracing the uncertainty that underlies them is crucial to understand the evolution of large and rapidly radiating lineages.

A new species of Iochroma Benth. (Solanaceae) from the eastern Andes of Colombia.

Iochromaorozcoae A.Orejuela & S.D.Sm., sp. nov. (Solanaceae) is described from the Andean forests of Cundinamarca in the eastern cordillera of Colombia. Iochromaorozcoae was first collected by the eminent Spanish priest and botanist José Celestino Mutis in the late part of the 18th century, but the specimens have lain unrecognised in herbaria for over 200 years. The species shares many features with its closest relative, Iochromabaumii S.D.Sm. & S.Leiva, but it differs from it in having small flowers with five corolla lobes and few inflorescences per branch, located near the shoot apex with 1 to 4 (-8) flowers, fruits that are greenish-yellow when ripe and its restricted geographic distribution. A description of I.orozcoae is provided, along with a detailed illustration, photographs of live plants, a comparison with closely-related species and a key to all Colombian species of Iochroma Benth. In closing, we emphasise the value of historical collections for the knowledge of biodiversity.

ResumenIochromaorozcoae A.Orejuela & S.D.Sm., sp. nov. (Solanaceae) se describe a partir de los bosques andinos de Cundinamarca, en la cordillera oriental de Colombia. Iochromaorozcoae fue recolectada por primera vez por el eminente sacerdote y botánico español José Celestino Mutis a finales del siglo XVIII, pero los especímenes han permanecido sin ser reconocidos en herbarios durante más de 200 años. La especie comparte muchas características con su pariente más cercano, Iochromabaumii S.D.Sm. & S.Leiva, pero difiere de esta en sus flores más pequeñas con cinco lóbulos de la corola y pocas inflorescencias por rama ubicadas cerca del ápice de la rama, con 1 a 4 (­8) flores por inflorescencia, frutos verde-amarillentos al madurar, y su distribución geográfica restringida. Se presenta una descripción de I.orozcoae, junto con una ilustración detallada, fotografías en vivo, una comparación con las especies cercanamente relacionadas y una clave para las especies colombianas de Iochroma Benth. Finalmente, enfatizamos el valor de las colecciones históricas para el conocimiento de la biodiversidad.

Monograph of Doselia (Solanaceae), a new hemiepiphytic genus endemic to the northern Andes.

A new genus, Doselia A.Orejuela & Särkinen, gen. nov., is described in the tribe Solandreae (Solanaceae) consisting of four species of hemiepiphytic lianas endemic to the premontane forests of the Colombian and Ecuadorian Andes. The genus is distinguished based on the membranous leaves, usually sparsely pubescent with eglandular simple trichomes, pseudo-verticillate leaf arrangement, and elongated, pendulous, and few-flowered inflorescences with showy flowers and conical fruits. Three new combinations are made to transfer species to the new genus previously described as part of the polyphyletic genus Markea Rich. (Doseliaepifita (S.Knapp) A.Orejuela & Särkinen, comb. nov., D.huilensis (A.Orejuela & J.M.Vélez) A.Orejuela & Särkinen, comb. nov. and D.lopezii (Hunz.) A.Orejuela & Särkinen, comb. nov.). One new species is described from the western slopes of the eastern cordillera of the Colombian Andes, known only from three localities in the Boyacá, Santander, and Tolima departments (Doseliagalilensis A.Orejuela & Villanueva, sp. nov.). The new species is unique in the genus in having glabrescent adult leaves, green-purplish calyces and long, greenish-white, infundibuliform corollas with delicate purplish veins and large lobes tinged with purple, and pubescent styles. Here we provide a revision of Doselia with a distribution map of all species, an identification key, photographs, preliminary conservation assessments, and line drawings of all four species.

ResumenUn nuevo género, Doselia A.Orejuela & Särkinen, gen. nov., es descrito en la tribu Solandreae (Solanaceae), conformado por cuatro especies de lianas hemiepífitas endémicas de los bosques premontanos de los Andes de Colombia y Ecuador. El género se distingue por sus hojas membranáceas con tricomas simples no glandulares, el arreglo pseudoverticilado de las hojas y sus inflorescencias paucifloras, largo pedunculadas y péndulas, flores vistosas y frutos cónicos. Se proponen tres nuevas combinaciones para acomodar especies previamente descritas en el polifilético género Markea Rich. (Doseliaepifita (S.Knapp) A.Orejuela & Särkinen, comb. nov., D.huilensis (A.Orejuela & J.M.Vélez) A.Orejuela & Särkinen, comb. nov. and D.lopezii (Hunz.) A.Orejuela & Särkinen, comb. nov.) Una nueva especie es descrita aquí proveniente de la vertiente occidental de la cordillera Oriental de los Andes colombianos, y conocida únicamente de tres localidades en los departamentos de Boyacá, Santander y Tolima (Doseliagalilensis A.Orejuela & Villanueva, sp. nov.). La nueva especie se caracteriza por sus hojas glabrescentes cuando adultas, cáliz verde-púrpura, corolas infundibuliformes grandes, blanco-verdosas con una reticulación fina de venas púrpuras, lóbulos corolinos grandes y teñidos de púrpura en su lado ventral y estilos pubescentes. El nuevo género es formalmente descrito incluyendo un mapa de distribución, una clave taxonómica y fotografías e ilustraciones para sus cuatro especies.