Steven Klosterman - Academia.edu (original) (raw)

Papers by Steven Klosterman

Phytobiomes Journal, 2021

The worldwide distribution of plant seeds can disseminate beneficial and plant-pathogenic microor... more The worldwide distribution of plant seeds can disseminate beneficial and plant-pathogenic microorganisms. This phenomenon is of particular concern where seed production is geographically isolated from crop production, as is the case with spinach in the United States. We aimed to characterize the structure and function of spinach seed microbiomes in commercial spinach seed lots originating from Europe and New Zealand. The seed lots we analyzed were infested with Peronospora effusa and Verticillium dahliae, only infested with V. dahliae, or not infested with either of these pathogens. The microbial taxonomic composition and gene function (assessed by gene ontology [GO] terms) of spinach seeds were highly influenced by geographic origin and the status of pathogen infestation. Through taxonomic profiling, we found that potentially plant-beneficial bacterial genera such as Pseudomonas and Pantoea were the most abundant taxa both in infested and noninfested seeds, and Stenotrophomonas was...

Suppression subtractive hybridization (SSH) was employed to identify lettuce (Lactuca sativa) gen... more Suppression subtractive hybridization (SSH) was employed to identify lettuce (Lactuca sativa) genes that are differentially expressed in symptomatic leaves infected with Verticillium dahliae. Genes expressed only in symptomatic leaves included those with homology to pathogenesis-related (PR) protein genes PR-3, PR-5, and a putative cysteine protease (LsCP2). Quantitative real-time reverse transcription PCR (RT-qPCR) revealed that LsCP2 was expressed in senescent leaves, but at significantly higher levels in symptomatic leaves. LsCP2 shares homology with plant cysteine proteases that are expressed in senescing leaves and may therefore accelerate or contribute to the leaf symptoms observed in a lettuceeV. dahliae interaction.

Physiological and Molecular Plant Pathology, 2011

Proceedings of the Canadian Engineering Education Association, Jun 17, 2013

We need to develop future engineering leaders who have the capability to lead teams in efficientl... more We need to develop future engineering leaders who have the capability to lead teams in efficiently and effectively delivering projects and products for their stakeholders.

Physiological and Molecular Plant Pathology, 2000

HortScience: a publication of the American Society for Horticultural Science

Verticillium wilt of lettuce caused by Verticillium dahliae can cause severe economic damage to l... more Verticillium wilt of lettuce caused by Verticillium dahliae can cause severe economic damage to lettuce producers. The pathogen exists as two races (Races 1 and 2) in lettuce, and complete resistance to Race 1 is known. Resistance to Race 2 isolates has not been reported, and production of Race 1-resistant cultivars will likely increase the frequency of Race 2 strains. The objective of this research was to select lettuce accessions for resistance to Race 2 isolates of V. dahliae. Two independent populations totaling 314 randomly sampled PIs were evaluated for Verticillium wilt disease incidence (DI) caused by V. dahliae isolate VdLs17 in one unreplicated and two replicated greenhouse experiments. Selection for PIs with reduced DI was conducted between each experiment and plant stems were plated on semiselective media to identify colonized plants that remained non-symptomatic. No accession with complete resistance was identified, although accessions with partial resistance were selec...

Annual Review of Phytopathology, 2014

The availability of genomic sequences of several Verticillium species triggered an explosion of g... more The availability of genomic sequences of several Verticillium species triggered an explosion of genome-scale investigations of mechanisms fundamental to the Verticillium lifecycle and disease process. Comparative genomics studies have revealed evolutionary mechanisms, like hybridization and interchromosomal rearrangements, that have shaped these genomes. Functional analyses of a diverse group of genes encoding virulence factors indicate that successful host xylem colonization relies on specific Verticillium responses to various stresses, including nutrient deficiency and host-defense derived oxidative stress. Regulatory pathways that control responses to changes in nutrient availability also appear to positively control resting structure development. Conversely, resting structure development seems to be repressed by pathways, such as those involving effector secretion, which promote responses to host defenses. The genomics-enabled functional characterization of responses to the challenges presented by the xylem environment, accompanied by identification of novel virulence factors, has rapidly expanded our understanding of niche adaptation in Verticillium species. Expected final online publication date for the Annual Review of Phytopathology Volume 53 is August 4, 2015. Please see http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates.

Twenty-two microsatellite loci were characterized in the soilborne plant pathogenic 8 fungus Vert... more Twenty-two microsatellite loci were characterized in the soilborne plant pathogenic 8 fungus Verticillium dahliae by analysis of the genome sequence. All loci were 9 polymorphic in at least two of three populations of V. dahliae from lettuce, spinach and 10 tomato. These loci were useful in genotyping isolates and highlighting differences in 11 genetic diversity among the three tested populations.

Molecular phylogenetics and evolution, Jan 12, 2015

Accurate species determination of plant pathogens is a prerequisite for their control and quarant... more Accurate species determination of plant pathogens is a prerequisite for their control and quarantine, and further for assessing their potential threat to crops. The family Peronosporaceae (Straminipila; Oomycota) consists of obligate biotrophic pathogens that cause downy mildew disease on angiosperms, including a large number of cultivated plants. In the largest downy mildew genus Peronospora, a phylogenetically complex clade includes the economically important downy mildew pathogens of spinach and beet, as well as the type species of the genus Peronospora. To resolve this complex clade at the species level and to infer evolutionary relationships among them, we used multi-locus phylogenetic analysis and species tree estimation. Both approaches discriminated all nine currently accepted species and revealed four previously unrecognized lineages, which are specific to a host genus or species. This is in line with a narrow species concept, i.e. that a downy mildew species is associated ...

The high mobility group (HMG) proteins are non-histone components of chromatin that regulate gene... more The high mobility group (HMG) proteins are non-histone components of chromatin that regulate gene expression via interactions with chromatin and transactivating protein factors. Plants and animals possess a family of HMG proteins that are similar on the basis of a shared motif known as the AT-hook, a domain that preferentially recognizes and binds to DNA with certain structural features, such as those imparted by AT-rich DNA. The animal HMG proteins with AT-hooks, collectively known as the HMGA family, have been studied extensively. As a consequence, much of the information available on the function of the animal HMGA family has been inferred to the plant HMG-I/Y family of AT-hook proteins. While both animal HMGA proteins and plant HMG-I/ Y proteins have AT-hook motifs, the overall structure of these proteins is quite different. Nevertheless, both plant and animal AThook proteins bind AT-rich tracts of DNA in the minor groove, induce DNA bending, and function in the regulation of gene expression. Based on detailed studies of HMGA-mediated regulation of mammalian genes, analogous mechanisms of HMG-I/Ymediated gene regulation in plants have been proposed. This review focuses primarily on the expression of the AT-hook HMG proteins and the proposed mechanisms by which these proteins regulate gene expression in plants and animals. An understanding of the variety of interactions of these proteins with chromatin in all eukaryotes is likely to provide insight into the regulatory properties of plant HMG-I/Y proteins. #

Applied Mycology and Biotechnology, 2005

Advances in Genetics, 2007

Ustilago maydis has emerged as an important model system for the study of fungi. Like many fungi,... more Ustilago maydis has emerged as an important model system for the study of fungi. Like many fungi, U. maydis undergoes remarkable morphological transitions throughout its life cycle. Fusion of compatible, budding, haploid cells leads to the production of a filamentous dikaryon that penetrates and colonizes the plant, culminating in the production of diploid teliospores within fungal-induced plant galls or tumors. These dramatic morphological transitions are controlled by components of various signaling pathways, including the pheromone-responsive MAP kinase and cAMP/PKA (cyclic AMP/protein kinase A) pathways, which coregulate the dimorphic switch and sexual development of U. maydis. These signaling pathways must somehow cooperate with the regulation of the cytoskeletal and cell cycle machinery. In this chapter, we provide an overview of these processes from pheromone perception and mating to gall production and sporulation in planta. Emphasis is placed on the genetic determinants of morphogenesis and pathogenic development of U. maydis and on the fungus-host interaction. Additionally, we review advances in the development of tools to study U. maydis, including the recently available genome sequence. We conclude with a brief assessment of current challenges and future directions for the genetic study of U. maydis.

Fungal Genetics and Biology, 2010

The fungal pathogen Verticillium dahliae has resulted in significant losses in numerous crops in ... more The fungal pathogen Verticillium dahliae has resulted in significant losses in numerous crops in coastal California, but lettuce remained unaffected until the mid-1990s. Since then outbreaks have decimated entire fields, but the causes of this sudden susceptibility of lettuce remain elusive. The population structure of V. dahliae isolated from coastal California (n = 123) was investigated with 22 microsatellite markers, and compared with strains from tomato in central California (n = 60), spinach seed imported from Washington State and Northern Europe (n = 43), and ornamentals from Wisconsin (n = 17). No significant differentiation was measured among hosts in coastal California or with the spinach and Wisconsin ornamental sampling groups. In contrast, the tomato sampling group was significantly differentiated. Significant gene flow was measured among the various geographic and host sampling groups, with the exception of tomato. Evidence of recombination in V. dahliae was identified through gametic disequilibrium and an exceedingly high genotypic diversity. The high incidence of V. dahliae in spinach seed and high planting density of the crop are sources of recurrent gene flow into coastal California, and may be associated with the recent outbreaks in lettuce.

Nature, Jan 29, 1998

The plant Arabidopsis thaliana (Arabidopsis) has become an important model species for the study ... more The plant Arabidopsis thaliana (Arabidopsis) has become an important model species for the study of many aspects of plant biology. The relatively small size of the nuclear genome and the availability of extensive physical maps of the five chromosomes provide a feasible basis for initiating sequencing of the five chromosomes. The YAC (yeast artificial chromosome)-based physical map of chromosome 4 was used to construct a sequence-ready map of cosmid and BAC (bacterial artificial chromosome) clones covering a 1.9-megabase (Mb) contiguous region, and the sequence of this region is reported here. Analysis of the sequence revealed an average gene density of one gene every 4.8 kilobases (kb), and 54% of the predicted genes had significant similarity to known genes. Other interesting features were found, such as the sequence of a disease-resistance gene locus, the distribution of retroelements, the frequent occurrence of clustered gene families, and the sequence of several classes of genes...

PLoS Pathogens, 2011

The vascular wilt fungi Verticillium dahliae and V. albo-atrum infect over 200 plant species, cau... more The vascular wilt fungi Verticillium dahliae and V. albo-atrum infect over 200 plant species, causing billions of dollars in annual crop losses. The characteristic wilt symptoms are a result of colonization and proliferation of the pathogens in the xylem vessels, which undergo fluctuations in osmolarity. To gain insights into the mechanisms that confer the organisms' pathogenicity and enable them to proliferate in the unique ecological niche of the plant vascular system, we sequenced the genomes of V. dahliae and V. albo-atrum and compared them to each other, and to the genome of Fusarium oxysporum, another fungal wilt pathogen. Our analyses identified a set of proteins that are shared among all three wilt pathogens, and present in few other fungal species. One of these is a homolog of a bacterial glucosyltransferase that synthesizes virulencerelated osmoregulated periplasmic glucans in bacteria. Pathogenicity tests of the corresponding V. dahliae glucosyltransferase gene deletion mutants indicate that the gene is required for full virulence in the Australian tobacco species Nicotiana benthamiana. Compared to other fungi, the two sequenced Verticillium genomes encode more pectindegrading enzymes and other carbohydrate-active enzymes, suggesting an extraordinary capacity to degrade plant pectin barricades. The high level of synteny between the two Verticillium assemblies highlighted four flexible genomic islands in V. dahliae that are enriched for transposable elements, and contain duplicated genes and genes that are important in signaling/transcriptional regulation and iron/lipid metabolism. Coupled with an enhanced capacity to degrade plant materials, these genomic islands may contribute to the expanded genetic diversity and virulence of V. dahliae, the primary causal agent of Verticillium wilts. Significantly, our study reveals insights into the genetic mechanisms of niche adaptation of fungal wilt pathogens, advances our understanding of the evolution and development of their pathogenesis, and sheds light on potential avenues for the development of novel disease management strategies to combat destructive wilt diseases.

Phytopathology, 2010

Maruthachalam, K., Atallah, Z. K., Vallad, G. E., Klosterman, S. J., Hayes, R. J., Davis, R. M., ... more Maruthachalam, K., Atallah, Z. K., Vallad, G. E., Klosterman, S. J., Hayes, R. J., Davis, R. M., and Subbarao, K. V. 2010. Molecular variation among isolates of Verticillium dahliae and polymerase chain reactionbased differentiation of races. Phytopathology 100:1222-1230.