Tertiary Origin and Pleistocene Diversification of Dragon Blood Tree (Dracaena cambodiana-Asparagaceae) Populations in the Asian Tropical Forests

Background

The origin of extraordinarily rich biodiversity in tropical forests is often attributed to evolution under stable climatic conditions over a long period or to climatic fluctuations during the recent Quaternary period. Here, we test these two hypotheses using Dracaena cambodiana, a plant species distributed in paleotropical forests.

Methods

We analyzed nucleotide sequence data of two chloroplast DNA (cpDNA: atpB-rbcL and trnD-trnT) regions and genotype data of six nuclear microsatellites from 15 populations (140 and 363 individuals, respectively) distributed in Indochina Peninsular and Hainan Island to infer the patterns of genetic diversity and phylogeographic structure. The population bottleneck and genetic drift were estimated based upon nuclear microsatellites data using the software programs BOTTLENECK and 2MOD. The lineage divergence times and past population dynamics based on cpDNA data were estimated using coalescent-based isolation-with-migration (IMa) and BEAST software programs.

Results

A significant phylogeographic structure (N _ST = 0.876, G _ST = 0.796, F _ST-SSR =0.329, R _ST =0.449; N _ST>G _ST, R _ST>F _ST-SSR, P<0.05) and genetic differentiation among populations were detected. Bottleneck analyses and Bayesian skyline plot suggested recent population reduction. The cpDNA haplotype network revealed the ancestral populations from the southern Indochina region expanded to northward. The most recent ancestor divergence time of D. cambodiana dated back to the Tertiary era and rapid diversification of terminal lineages corresponded to the Quaternary period.

Conclusions

The results indicated that the present distribution of genetic diversity in D. cambodiana was an outcome of Tertiary dispersal and rapid divergence during the Quaternary period under limited gene flow influenced by the uplift of Himalayan-Tibetan Plateau and Quaternary climatic fluctuations respectively. Evolutionary processes, such as extinction-recolonization during the Pleistocene may have contributed to the fast diversification in D. cambodiana.     

Talaromyces marneffei Outside Endemic Areas in India: an Emerging Infection with Atypical Clinical Presentations and Review of Published Reports from India

Mycopathologia - Talaromycosis is a disseminated disease caused by Talaromyces (Penicillium) marneffei, mainly seen in acquired immunodeficiency syndrome (AIDS) patients. Its distribution is...     

Non-Healing Ulcer Due to Trichosporon loubieri in an Immunocompetent Host and Review of Published Reports

We report here a case of non-healing ulcer due to Trichosporon loubieri in an apparently immunocompetent female. The identity of isolate was confirmed by DNA sequencing of D1/D2 region of 26S rDNA. The minimum inhibitory concentrations of the isolate were amphotericin B—0.5 μg/ml; fluconazole—4 μg/ml; posaconazole—0.25 μg/ml; voriconazole—0.06 μg/ml. The patient was managed by extensive debridement and oral fluconazole 150 mg daily for 6 weeks. She responded to therapy. To the best of our knowledge, till date, this is the fourth report of human infection due to T. loubieri and the first of its kind in an immunocompetent host. A review of published literature on infections due to T. loubieri is also included.     

Aspergillus terreus Causing Probable Invasive Aspergillosis in a Patient with Cystic Fibrosis

Mycopathologia - Aspergillus terreus may colonize the airways of patients with cystic fibrosis (CF). Whether this merits antifungal treatment is still unclear due to heterogeneous reports regarding...     

Serum glucose-regulated protein 78 (GRP78) levels in COVID-19-associated mucormycosis: results of a case–control study

Mycopathologia - In experimental models, the expression of glucose-regulated protein 78 (GRP78) in endothelial cells played a role in the pathogenesis of mucormycosis. However, the role of GRP78 in...     

Detection of dideoxyosone intermediates of glycation using a monoclonal antibody: characterization of major epitope structures

Glycation or the Maillard reaction in proteins forms advanced glycation end products (AGEs) that contribute to age- and diabetes-associated changes in tissues. Dideoxyosones, which are formed by the long-range carbonyl shift of the Amadori product, are newly discovered intermediates in the process of AGE formation in proteins. They react with o-phenylenediamine (OPD) to produce quinoxalines. We developed a monoclonal antibody against 2-methylquinoxaline-6-carboxylate coupled to keyhole limpet hemocyanin. The antibody reacted strongly with ribose and fructose (+OPD)-modified RNase A and weakly with glucose and ascorbate (+OPD)-modified RNase A. Reaction with substituted quinoxalines indicated that this antibody favored the 2-methyl group on the quinoxaline ring. We used high performance liquid chromatography to isolate and purify three antibody-reactive products from a reaction mixture of N alpha-hippuryl-L-lysine+ribose+OPD. The two most reactive products were identified as diastereoisomers of N1-benzoylglycyl-N6-(2-hydroxy-3-quinoxalin-2-ylpropyl)lysine and the other less reactive product as N1-benzoylglycyl-N6-[2-hydroxy-2-(3-methylquinoxalin-2-yl)ethyl]lysine. Our study confirms that dideoxyosone intermediates form during glycation and offers a new tool for the study of this important pathway in diabetes and aging.     

PD-1-dependent mechanisms maintain peripheral tolerance of donor-reactive CD8+ T cells to transplanted tissue

Peripheral mechanisms of self-tolerance often depend on the quiescent state of the immune system. To what degree such mechanisms can be engaged in the enhancement of allograft survival is unclear. To examine the role of the PD-1 pathway in the maintenance of graft survival following blockade of costimulatory pathways, we used a single-Ag mismatch model of graft rejection where we could track the donor-specific cells as they developed endogenously and emerged from the thymus. We found that graft-specific T cells arising under physiologic developmental conditions at low frequency were actively deleted at the time of transplantation under combined CD28/CD40L blockade. However, this deletion was incomplete, and donor-specific cells that failed to undergo deletion up-regulated expression of PD-1. Furthermore, blockade of PD-1 signaling on these cells via in vivo treatment with anti-PD-1 mAb resulted in rapid expansion of donor-specific T cells and graft loss. These results suggest that the PD-1 pathway was engaged in the continued regulation of the low-frequency graft-specific immune response and thus in maintenance of graft survival.     

Distal Lateral Subungual Onychomycosis Owing to <Emphasis Type="Italic">Tritirachium oryzae</Emphasis>: A Bystander or Invader?

The genus Tritirachium is a mitosporic fungus which inhabits in soil and decaying plant material and also a notable insect pathogen. Human infections with Tritirachium species though rare were previously reported to cause corneal ulcers, otomycosis, onychomycosis, and dermatomycosis of the scalp and hence may be considered as a potential pathogen. Here we report a case of distal lateral subungual onychomycosis involving right great toenail in a 22-year-old female, wherein direct potassium hydroxide preparations, fungal cultures, and molecular sequencing of the isolate established Tritirachium oryzae as the etiological agent. Antifungal susceptibility performed by the microbroth technique of CLSI revealed increased MICs to amphotericin B and low MICs to azoles and echinocandins. The case was managed with surgical nail avulsion followed by topical application of 2% ketoconazole cream resulting regrowth of normal nail. To the best of our knowledge, this is the first report of non-dermatophytic mold T. oryzae causing onychomycosis in India.     

Ochroconis humicola Coexisting with Esthesioneuroblastoma: An Incidental Coloniser or Allergen?

Ochroconis humicola, a fish pathogen, is rarely reported to cause disease in human. We report its first isolation from nasal tissue of a human immunodeficiency virus-positive young female patient. Histopathologically, the nasal mass was diagnosed as esthesioneuroblastoma. She presented with right-sided nasal obstruction and bleeding for two and half months. Computed tomography scan showed the nasal mass filling the whole right nasal cavity, maxillary, ethmoid and sphenoid sinuses. The direct microscopy of the nasal tissue and mucin demonstrated the presence of septate hyphae. On culture, O. humicola was isolated from the same tissue and the fungus was identified by morphologic, physiologic and molecular data including sequencing of ITS and 28S rDNA regions. No antifungal was prescribed, and the whole mass was resected out by endoscopic surgery. The patient was treated further by radical radiotherapy. After 1 year of follow-up, patient is stable with no recurrence of tumour. The role of this fungus was not clear, as it may be bystander or producing allergic fungal rhinosinusitis.