Biology subjects

Broders, K.

Publications and source records attributed to Broders, K..

7 recordsLinked to original sources

bioRxiv2024

Plant responses to wheat curl mites and wheat streak mosaic virus (WSMV): first evidence of virus tolerance in wheat

Wheat curl mites (WCM) are arthropod pests that pose significant threats to wheat crops by causing direct damage by feeding, and transmitting viruses such as Wheat Streak Mosaic Virus (WSMV), Triticum Mosaic Virus (TriMV), and High Plains Wheat Mosaic Virus (HPWMoV), leading to substantial losses in wheat, barley, oats, and rye. Over three years of field screening, we found that the cultivar Hatcher consistently produced higher yields under high WSMV disease pressure, outperforming Mace and TAM112, which carry the Wsm1 gene and a QTL for curl mite resistance, respectively, indicating tolerance. To investigate the mechanisms underlying the tolerance phenotype in Hatcher, we compared its response to WCM and WSMV infection with a susceptible genotype, CO15D173R. Transcriptomic analysis revealed a nuanced interplay between plant defense and growth in Hatcher, with upregulation of genes related to jasmonic acid (JA), salicylic acid (SA), and abscisic acid (ABA) pathways, indicating a coordinated defense response. The activation of lignin biosynthesis genes points to a potential role of cell wall strengthening in deterring WCM and WSMV. Additionally, the regulation of genes involved in growth-related hormonal pathways such as gibberellic acid (GA), and brassinosteroids (BR) highlights Hatchers ability to maintain growth disease pressure. Our findings provide insight into the intricate network of phytohormones, growth-defense trade-offs, and cell wall modifications contributing to Hatchers tolerance to WCM and WSMV. This knowledge can inform the development of tolerant wheat varieties and enhance integrated pest management strategies, ultimately safeguarding wheat production.

plant biology↗

bioRxiv2024

Oomycete communities in lowland tropical forest soils vary in abundance and are composed of saprophytes and pathogens of seeds and seedlings of multiple plant species.

PremiseThe soils in lowland tropics are teeming with microbial life which can impact plant community structure and diversity through plant-soil feedbacks. While bacteria and fungi have been the focus of most studies in the tropics, the oomycetes may have an outsized effect on seed and seedling health and survival, given their affinity for environments with increased precipitation and temperature. MethodsWe assessed the diversity and pathogenicity of oomycete species present in a lowland tropical forest in Panama. We used both a culture dependent leaf-baiting assay and culture independent soil DNA metabarcoding methods to quantify zoospore abundance and species diversity. A subset of the isolates from the baiting assay were used to evaluate pathogenicity and aggressiveness on seedlings of three tree species. Key resultsOomycetes are ubiquitous and common members of the soil microbial community in lowland tropical forests and zoospore abundance was far greater compared to similar studies from temperate and mediterranean forests. We also observed variation in oomycete species ability to infect host plants. Species of Pythium were more aggressive, while species of Phytopythium caused less disease but were more diverse and commonly isolated from the soil. Finally, we found that individual hosts accumulate a distinct oomycete community and was the only factor that had an effect community structure. ConclusionsCollectively, these finding demonstrate that oomycetes are ubiquitous, host-generalist pathogens and saprophytes, that have the potential to impact seed and seedling survival in lowland tropical forests

ecology↗

bioRxiv2020

Host-generalist fungal pathogens of seedlings may maintain forest diversity via host-specific impacts and differential susceptibility among tree species

O_LIHost-specialized pathogens are credited with the maintenance of tropical forest diversity under the Janzen-Connell hypothesis. Yet, in diverse forests, selection may favor pathogens with broad host ranges given their passive dispersal and the relative rarity of tree species. C_LIO_LIWe surveyed the host associations of potential pathogens isolated from symptomatic seedlings in the forests in Panama and used inoculations to assess: (i) the pathogenicity and host ranges of 27 fungal isolates, and (ii) differences among tree species in susceptibility. C_LIO_LIThirty-one of the 33 non-singleton OTUs isolated from seedlings are multi-host. All 31 multi-host OTUs exhibit low to moderate specialization, and we observed phylogenetically overdispersed host use for 19 OTUs. The pathogenicity of 10 isolates was experimentally confirmed; nine caused disease in seedlings in multiple families. However, the outcome of infection differs among tree species susceptible to a given multi-host pathogen. Furthermore, some tree species were seemingly resistant to all fungi tested, while others were susceptible to multiple fungi. Tree species adapted to environments with lower disease pressure were most likely to exhibit disease. C_LIO_LIOur results suggest that generalist pathogens contribute to the maintenance of local and regional forest diversity via host-specific impacts and the exclusion of disease-sensitive trees from disease-prone habitats. C_LI

ecology↗

bioRxiv2019

The genome of the butternut canker pathogen, Ophiognomonia clavigignenti-juglandacearum shows an elevated number of genes associated with secondary metabolism and protection from host resistance responses in comparison with other members of the Diaporthales

Ophiognomonia clavigignentijuglandacearum (Oc-j) is a plant pathogenic fungus that causes canker and branch dieback diseases in the hardwood tree butternut, Juglans cinerea. Oc-j is a member of the order of Diaporthales, which includes many other plant pathogenic species, several of which also infect hardwood tree species. In this study, we sequenced the genome of Oc-j and achieved a high-quality assembly and delineated the phylogeny of Oc-j within the Diaporthales order using a genome-wide multi-gene approach. We also further examined multiple gene families that might be involved in plant pathogenicity and degradation of complex biomass, which are relevant to a pathogenic life-style in a tree host. We found that the Oc-j genome contains a greater number of genes in these gene families compared to other species in Diaporthales. These gene families include secreted CAZymes, kinases, cytochrome P450, efflux pumps, and secondary metabolism gene clusters. The large numbers of these genes provide Oc-j with an arsenal to cope with the specific ecological niche as a pathogen of the butternut tree.

genomics↗

bioRxiv2019

Genomic acquisitions in emerging populations of Xanthomonas vasicola pv. vasculorum infecting corn in the U.S. and Argentina

Xanthomonas vasicola pv. vasculorum (Xvv) is an emerging bacterial plant pathogen that causes bacterial leaf streak on corn. First described in South Africa in 1949, reports of this bacteria have greatly increased in the past years in South America and in the U.S., where it is now present in most of the corn producing states. Phenotypic characterization showed that the emerging U.S. and South American Xvv populations may have increased virulence in corn compared to older strains. To understand the genetic mechanisms behind the increased virulence in this group, we used comparative genomics to identify gene acquisitions in Xvv genomes from the U.S. and Argentina. We sequenced 41 genomes of Xvv and the related sorghum-infecting X. vasicola pv. holcicola (Xvh). A comparison of all available X. vasicola genomes showed the phylogenetic relationships in the group and identified clusters of genes associated with the emerging Xvv populations. The newly acquired gene clusters showed evidence of horizontal transfer to Xvv and included candidate virulence factors. One cluster, in particular, corresponded to a prophage transferred from Xvh to all Xvv from Argentina and the U.S. The prophage contains putative secreted proteins, which represent candidates for virulence determinants in these populations and await further molecular characterization.

microbiology↗

bioRxiv2019

Transfer of Xanthomonas campestris pv. arecae, and Xanthomonas campestris pv. musacearum to Xanthomonas vasicola (Vauterin) as Xanthomonas vasicola pv. arecae comb. nov., and Xanthomonas vasicola pv. musacearum comb. nov. and description of Xanthomonas vasicola pv. vasculorum pv. nov.

LETTER TO THE EDITOR LETTER TO THE EDITOR EMENDED DESCRIPTION OF... REFERENCES Members of the genus Xanthomonas, within the gamma-Proteobacteria, collectively cause disease on more than 400 plant species (Hayward 1993), though some members are apparently non-pathogenic (Vauterin et al. 1996) and some have been isolated from clinical samples such as skin microbiota (Seite, Zelenkova, and Martin 2017). Historically, taxonomy of Xanthomonas was tied to the host of isolation (Starr 1981; Wernham 1948), with the genus being split into large numbers of species, each defined by this single phenotypic feature (Dye 1962). Subsequently, most of the species were transferred (lumped) into a single species, X. campestris, and designated as nomenspec ...

microbiology↗

bioRxiv2016

Comparative genomics of beetle-vectored fungal pathogens reveals a reduction in genome size and independent evolution of pathogenicity of two tree pathogens

O_LIGeosmithia morbida is an emerging fungal pathogen which serves as a paradigm for examining the evolutionary processes behind pathogenicity because it is one of two known pathogens within a genus of mostly saprophytic, beetle-associated, fungi. This pathogen causes thousand cankers disease in black walnut trees and is vectored into the host via the walnut twig beetle. G. morbida was first detected in western US and currently threatens the timber industry concentrated in eastern US.\nC_LIO_LIWe sequenced the genomes of G. morbida and two non-pathogenic Geosmithia species and compared these species to other fungal pathogens and nonpathogens to identify genes under positive selection in G. morbida that may be associated with pathogenicity.\nC_LIO_LIG. morbida possesses one of the smallest genomes among the fungal species observed in this study, and one of the smallest fungal pathogen genomes to date. The enzymatic profile is this pathogen is very similar to its relatives.\nC_LIO_LIOur findings indicate that genome reduction is an important adaptation during the evolution of a specialized lifestyle in fungal species that occupy a specific niche, such as beetle vectored tree pathogens. We also present potential genes under selection in G. morbida that could be important for adaptation to a pathogenic lifestyle.\nC_LI

evolutionary biology↗