Showing papers by "Ali H. Bahkali published in 2012"

The Genomes of the Fungal Plant Pathogens Cladosporium fulvum and Dothistroma septosporum Reveal Adaptation to Different Hosts and Lifestyles But Also Signatures of Common Ancestry

Abstract: We sequenced and compared the genomes of the Dothideomycete fungal plant pathogens Cladosporium fulvum (Cfu) (syn. Passalora fulva) and Dothistroma septosporum (Dse) that are closely related phylogenetically, but have different lifestyles and hosts. Although both fungi grow extracellularly in close contact with host mesophyll cells, Cfu is a biotroph infecting tomato, while Dse is a hemibiotroph infecting pine. The genomes of these fungi have a similar set of genes (70% of gene content in both genomes are homologs), but differ significantly in size (Cfu >61.1-Mb; Dse 31.2-Mb), which is mainly due to the difference in repeat content (47.2% in Cfu versus 3.2% in Dse). Recent adaptation to different lifestyles and hosts is suggested by diverged sets of genes. Cfu contains an α-tomatinase gene that we predict might be required for detoxification of tomatine, while this gene is absent in Dse. Many genes encoding secreted proteins are unique to each species and the repeat-rich areas in Cfu are enriched for these species-specific genes. In contrast, conserved genes suggest common host ancestry. Homologs of Cfu effector genes, including Ecp2 and Avr4, are present in Dse and induce a Cf-Ecp2- and Cf-4-mediated hypersensitive response, respectively. Strikingly, genes involved in production of the toxin dothistromin, a likely virulence factor for Dse, are conserved in Cfu, but their expression differs markedly with essentially no expression by Cfu in planta. Likewise, Cfu has a carbohydrate-degrading enzyme catalog that is more similar to that of necrotrophs or hemibiotrophs and a larger pectinolytic gene arsenal than Dse, but many of these genes are not expressed in planta or are pseudogenized. Overall, comparison of their genomes suggests that these closely related plant pathogens had a common ancestral host but since adapted to different hosts and lifestyles by a combination of differentiated gene content, pseudogenization, and gene regulation.

Medicinal mushrooms in prevention and control of diabetes mellitus

Abstract: Diabetes mellitus is a life-threatening chronic metabolic disease caused by lack of insulin and/or insulin dysfunction, characterized by high levels of glucose in the blood (hyperglycemia). Millions worldwide suffer from diabetes and its complications. Significantly, it has been recognized that type 2 diabetes is an important preventable disease and can be avoided or delayed by lifestyle intervention. Presently, there are many chemical and biochemical hypoglycemic agents (synthetic drugs), that are used in treating diabetes and are effective in controlling hyperglycemia. However, as they may have harmful side-effects and fail to significantly alter the course of diabetic complications, natural anti-diabetic drugs from medicinal plants have attracted a great deal of attention. Medicinal mushrooms have been valued as a traditional source of natural bioactive compounds over many centuries and have been targeted as potential hypoglycemic and anti-diabetic agents. Bioactive metabolites including polysaccharides, proteins, dietary fibres, and many other biomolecules isolated from medicinal mushrooms and their cultured mycelia have been shown to be successful in diabetes treatment as biological anti-hyperglycemic agents. In this review we discuss the biological nature of diabetes and, in particular, explore some promising mushrooms that have experimental anti-diabetic properties, preventing or reducing the development of diabetes mellitus. The importance of medicinal mushrooms as agents of medical nutrition therapy and how their metabolites can be used as supportive candidates for prevention and control of diabetes is explored. Future prospects for this field of study and the difficulties and constraints that might affect the development of rational drug products from medicinal mushrooms are discussed.

Medicinal mushrooms in supportive cancer therapies: an approach to anti-cancer effects and putative mechanisms of action

Abstract: Medicinal mushrooms have been valued as natural sources of bioactive compounds since times immemorial and have been recognized as potential immunomodulating and anti-cancer agents. Their consumption has consistently been shown to have beneficial effects on human health. Cancer is a generic term for several types of diseases that can be chronic and are responsible for a large number of deaths worldwide. Although there has been considerable progress in modern cancer therapy research, difficulties in understanding the molecular behavior of various types of cancers and the numerous side effects experienced by patients from treatments means that this whole subject area is still problematic. Thus, biological immunotherapy using natural bioactive compounds as supportive treatments in conventional cancer therapies has become in vogue. Bioactive metabolites isolated from medicinal mushrooms have shown potential successes in cancer treatment as biological immunotherapeutic agents that stimulate the immune system against cancer cells. They also act as an effective source of anti-cancer agents, capable of interfering with cellular signal transduction pathways linked to cancer development and progression. In this review we compile available data on the characteristics of medicinal mushrooms that appear to be particularly effective as biological immunotherapeutic agents. Major consideration is given to biological constituents and the putative mechanisms of action by which bioactive compounds act on the human body. Consideration is also given to the benefits that have been claimed for the use of mushrooms in treating cancer and the future prospects of using medicinal mushrooms as potent supportive candidate bioagents for treatment of cancers is discussed.

A multi-locus backbone tree for Pestalotiopsis, with a polyphasic characterization of 14 new species

Abstract: Pestalotiopsis is a taxonomically confused, pathogenic and chemically creative genus requiring a critical re-examination using a multi-gene phylogeny based on ex-type and ex-epitype cultures. In this study 40 isolates of Pestalotiopsis, comprised of 28 strains collected from living and dead plant material of various host plants from China were studied by means of morphology and analysis of ITS, β–tubulin and tef1 gene sequence data. Based on molecular and morphological data we describe 14 new species (Pestalotiopsis asiatica, P. chinensis, P. chrysea, P. clavata, P. diversiseta, P. ellipsospora, P. inflexa, P. intermedia, P. linearis, P. rosea, P. saprophyta, P. umberspora, P. unicolor and P. verruculosa) and three species are epitypified (P. adusta, P. clavispora and P. foedans). Of the 10 gene regions (ACT, β-tubulin, CAL, GPDH, GS, ITS, LSU, RPB 1, SSU and tef1) utilized to resolve cryptic Pestalotiopsis species, ITS, β–tubulin and tef1 proved to be the better markers. The other gene regions were less useful due to poor success in PCR amplification and/or in their ability to resolve species boundaries. As a single gene tef1 met the requirements for an ideal candidate and functions well for species delimitation due to its better species resolution and PCR success. Although β-tubulin showed fairly good differences among species, a combination of ITS, β-tubulin and tef1 gene data gave the best resolution as compared to single gene analysis. This work provides a backbone tree for 22 ex-type/epitypified species of Pestalotiopsis and can be used in future studies of the genus.

Trichomeriaceae, a new sooty mould family of Chaetothyriales

Abstract: Trichomerium is a genus of foliar epiphytes with the appearance of sooty moulds, mostly occurring on the surface of living leaves and apparently gaining their nutrients from insect exudates. Species have ascostromata with setae and develop on a loosely interwoven mycelial mass of dark brown hyphae, while asci have a bitunicate appearance with hyaline ascospores. In this study, we made 16 collections of Trichomerium from Thailand. All were isolated, and the LSU and ITS rDNA gene regions sequenced. Phylogenetic analysis indicated that the Trichomerium species form a monophyletic clade within Chaetothyriales and warrant the introduction of a new family Trichomeriaceae. Bootstrap support for the Chaetothyriales is 100 % and clearly separates Trichomeriaceae from Capnodiales which are morphologically very similar. A detailed account of Trichomerium is provided and we describe and illustrate three new species based on morphological and molecular data. We propose that T. foliicola is adopted as the generic type of Trichomerium because it has been impossible to obtain the holotype specimen of T. coffeicola and also no molecular data exists in worldwide databases for this species or genus.

Agaricus subrufescens: new to Thailand

Abstract: Agaricus subrufescens is an edible and medicinal mushroom of Agaricaceae, Agaricales originally described from North America. It has increasingly been used as a health food and alternative medicine and is also used in cosmetics. Agaricus subrufescens has been shown to exhibit many pharmaceutical traits such as anti-cancer, anti-microbial and immunomodulatory properties and is rich in bioactive compounds, especially beta-glucans. Recently, four specimens of Agaricus subrufescens were collected from northern Thailand and are the first records of this taxon for Thailand and surrounding regions. The data from macro-and microscopic features are consistent with the characteristics of the species. The molecular data indicates the Thai collections cluster in A. subrufescens sensu lato. The species is reported here because of the significance of finding this very important taxon in Thailand which has both commercial and biotechnological potential.

Lentinus giganteus revisited: new collections from Sri Lanka and Thailand

Abstract: A new collection of Lentinus giganteus from Sri Lanka, where it was originally described, is used to epitypify the species after comparison with the type protologue and drawings held in Peradeniya, Sri Lanka; a full description and illustrations are provided. Additional collections were made at three sites in northern Thailand. Phylogenetic ITS-1-5.8S-ITS2 rDNA sequence analyses using maximum likelihood, maximum parsimony and Bayesian inference all support the transfer of L. giganteus to Pleurotus. Although the collections from Thailand differ slightly morphologically and phylogenetically from P. giganteus sensu stricto, these differences do not yet merit specific status. Instead, P. giganteus is maintained as one widely variable species represented by relatively large fruiting bodies. Saprobic on buried well-rotted wood in forests, P. giganteus is widely consumed in Sri Lanka and might be profitably cultivated in Thailand.

Characterization of Novel Di-, Tri-, and Tetranucleotide Microsatellite Primers Suitable for Genotyping Various Plant Pathogenic Fungi with Special Emphasis on Fusaria and Mycospherella graminicola

Abstract: The goals of this investigation were to identify and evaluate the use of polymorphic microsatellite marker (PMM) analysis for molecular typing of seventeen plant pathogenic fungi. Primers for di-, tri-, and tetranucleotide loci were designed directly from the recently published genomic sequence of Mycospherlla graminicola and Fusarium graminearum. A total of 20 new microsatellite primers as easy-to-score markers were developed. Microsatellite primer PCR (MP-PCR) yielded highly reproducible and complex genomic fingerprints, with several bands ranging in size from 200 to 3000 bp. Of the 20 primers tested, only (TAGG)4, (TCC)5 and (CA)7T produced a high number of polymorphic bands from either F. graminearum or F. culmorum. (ATG)5 led to successful amplifications in M. graminicola isolates collected from Germany. Percentage of polymorphic bands among Fusarium species ranged from 9 to 100%. Cluster analysis of banding patterns of the isolates corresponded well to the established species delineations based on morphology and other methods of phylogenetic analysis. The current research demonstrates that the newly designed microsatellite primers are reliable, sensitive and technically simple tools for assaying genetic variability in plant pathogenic fungi.

Aquapeziza: a new genus from freshwater and its morphological and phylogenetic relationships to Pezizaceae

Abstract: An investigation of freshwater fungi on submerged wood in southwestern China led to the discovery of a new discomycete species from a small stream in Yunnan Province. The taxon is characterized morphologically by its combined characters of epigenous, white ascomata, ovoid, amyloid asci and multi-guttulate, single-celled, smooth, globose ascospores. Because the taxon cannot be accommodated in any known genus based on morphological characters and molecular data (28S and ITS rDNA sequences) a new genus and species Aquapeziza globispora is proposed to accommodate it. The new genus is circumscribed and a description and illustrations of the new species are provided. Relationships of Aquapeziza in Pezizaceae are inferred from 28S and ITS rDNA sequence analyses.

Some stromatic pyrenomycetous fungi from northern Thailand - 1. Biscogniuxia , Camillea and Hypoxylon (Xylariaceae)

Abstract: Fourteen species of stromatic pyrenomycetous fungi (family Xylariaceae) collected in northern Thailand are discussed. Six of these (Biscogniauxia lithocarpi, Camillea malaysiensis var. macrospora, Hypoxylon juventuterubrum, H. pseudoretpela, H. rubroargillaceum, and H. sepipigmentum) are described as taxa new to science. Illustrations of these taxa are provided, and they are compared with similar taxa known from the Western Hemisphere.

Use of the Saccharomyces cerevisiae endopolygalacturonase promoter to direct expression in Escherichia coli

Abstract: In Saccharomyces cerevisiae, an endopolygalacturonase encoded by the PGL1 gene catalyzes the random hydrolysis of the α-1,4 glycosidic linkages in polygalacturonic acid. To study the regulation of the PGL1 gene, we constructed a reporter vector containing the lacZ gene under the control of PGL1 promoter. Surprisingly, when Escherichia coli DH5α was transformed by this vector, cells harboring the constructed plasmid produced blue colonies. Sequence analysis of this promoter revealed that E. coli consensus sequences required to express an in-frame lacZ alpha product were present. We next decided to investigate how the PGL1 promoter is regulated in E. coli compared to yeast. In this study, we examined the modulation of the PGL1 promoter in E. coli, and the results indicated that its activity is greatly induced by saturated digalacturonic acid and is indirectly regulated by the transcriptional regulators the 2-keto-3-deoxygluconate repressor. Moreover, PGL1 expression is enhanced under aerobic conditions. We found that β-galactosidase activity in E. coli could reach 180 units, which is 40-fold greater than the activity produced in S. cerevisiae, and greater than recombinant protein expression previously reported by other researchers. We thus demonstrate that this vector can be considered as a dual expression plasmid for both E. coli and S. cerevisiae hosts. So far, no modulation of endoPG promoters expressed in E. coli has been reported.