Biology subjects

Heiden, N.

Publications and source records attributed to Heiden, N..

5 recordsLinked to original sources

bioRxiv2025

Effector loss and gain drives pathogen host range at a fitness cost

Epidemic preparedness depends on tracking microbial evolution that drives shifts in ecological behaviors such as disease emergence. However, the genetic constraints for microbial host adaptation to emerge for generalist and specialist behaviors remain poorly described. Here, we show that generalist cereal pathogen Xanthomonas translucens arose from a specialist ancestor via the loss of a single effector gene, xopAL1. Deleting barley-specialist X. translucens xopAL1 recapitulated the host jump to wheat and demonstrates risk across each globally distributed genetic lineage. However, this niche expansion via XopAL1 loss incurs a significant pathogenic fitness cost to colonize barley. Moreover, the specialist lineage gained an additional effector gene, xopAJ, which enhanced virulence on barley while restricting oat infection, thereby reinforcing niche specialization. We further identified key host pathways mediating resistance to the specialist lineage of X. translucens, opening avenues for potentially identifying targets for crop improvement. Our work provides an experimentally validated evolutionary framework to understand mechanisms of intergenera host jump. Overall, we demonstrate that single events of gene loss and gain shape ecological behaviors of pathogens by creating a dynamic trade-off between niche breadth and specialization.

microbiology↗

bioRxiv2024

Barley variety Quest exhibits broad-spectrum, moderate quantitative resistance against diverse Xanthomonas translucens pathovar translucens

Barley (Hordeum vulgare subspp. vulgare) is the fourth most widely produced cereal today and is valuable for both animal and human consumption. Bacterial leaf streak (BLS) of barley is caused primarily by X. translucens pv. translucens (Xtt) and can lead to significant yield losses. There are currently no available control methods for BLS pathogens, but there are ongoing efforts to identify and characterize sources of resistance to Xtt in available barley germplasm. These screening projects require field trials which are time-consuming and challenged due to variables introduced by environmental and weather conditions, field conditions and other organisms that may be present. Reliable greenhouse phenotyping techniques are needed to accelerate screening of barley germplasm against more Xtt strains. In this study, we established a rapid greenhouse spray inoculation protocol for pathogen-plant phenotyping. This provides a framework for rapid germplasm screening before time-consuming and limited field nursery trials. Our method confirmed the moderate quantitative resistance phenotype discovered in field trials for the cultivars Quest and Tradition against the Xtt strain CIX95. One week old seedlings of the previously characterized resistant line PI329000 were not resistant relative to the susceptible check line MW14-5371-013. The cultivar Quest then demonstrated moderate quantitative resistance against a diverse panel of Xtt strains. Xtt subgroup did not influence BLS outcomes on tested barley lines. We found evidence to support the hypothesis that the virulence of modern strains is increasing, though this does not improve their ability to cause disease on Quest.

microbiology↗

bioRxiv2024

rpfF is not required for X. translucens pv. undulosa pathogenesis

Bacterial cells self-coordinate via a mechanism called quorum sensing. In Xanthomonas species the gene rpfF encodes the quorum sensing autoinducer synthase. Xanthomonas species are divided into two main phylogenetic groups called Clade I and Clade II. The rpf quorum sensing system has been well studied in multiple Clade II Xanthomonas species and deletion of rpfF resulted in a major loss of virulence on susceptible hosts. However, the only Clade I Xanthomonas species in which the rpfF system was previously studied was in the sugarcane pathogen X. albilineans. In X. albilineans the rpf cluster plays a relatively small role in pathogenesis. Xanthomonas translucens pv. undulosa (Xtu) is a Clade I Xanthomonas species that causes bacterial leaf streak (BLS) and black chaff of wheat and barley and has increased as a concern in recent decades. Neither major resistance nor chemical treatments are available to prevent disease caused by Xtu. Interference with rpf bacterial quorum sensing systems has demonstrated some success in other systems. It was unknown whether BLS caused by Xtu could be prevented via quorum sensing interference. We found that Xtu encodes an rpfF homolog and we created an rpfF knockout mutant to study the role of the rpf system in Xtu. We found that the rpfF mutant was unaffected in its pathogenesis as it caused BLS symptoms and multiplied within wheat plants to the same levels as the wildtype strain. The Xtu rpfF mutant grew normally in lag and log phases in vitro, however it exhibited a shorter stationary phase and an early death phase in plant-derived media. The importance of RpfF in Xtus life cycle is unknown, though it appears to carry out a role in population stability. Our research determined that rpfF is not a major Xtu pathogenicity factor. Therefore, we do not recommend the targeting of the rpf quorum sensing system as a preventative treatment for BLS of wheat.

molecular biology↗

bioRxiv2022

Comparative genomics of Minnesotan barley-infecting Xanthomonas translucens shows overall genomic similarity but virulence factor diversity

Xanthomonas translucens pv. translucens (Xtt) is a global barley pathogen and a concern for resistance breeding and regulation. Long-read whole genome sequences allow in-depth understanding of pathogen diversity. We have completed long-read PacBio sequencing of two Minnesotan Xtt strains and an in-depth analysis of available Xtt genomes. We found that average nucleotide identity(ANI)-based approaches organize Xtt strains differently than the previously standard MLSA approach. According to ANI, Xtt forms a separate clade from Xanthomonas translucens pv. undulosa and consists of three main groups which are represented on multiple continents. The global distribution of Xtt groups suggests that regulation of seed is not important for prevention of Xtt spread. Some virulence factors, such as 17 Type III-secreted effectors, are highly conserved and offer potential targets for the elicitation of broad resistance. However, there is a high degree of variation in virulence factors meaning that germplasm should be screened for resistance with a diverse panel of Xtt.

genomics↗

bioRxiv2021

Do soil features condition seed germination of gypsum plants? An analysis of the effect of different natural soils

Gypseous soils are widespread across arid and semiarid environments worldwide. They present remarkable challenges to plants and host a unique flora. We aimed to assess up to what point the specificity and distribution of species on gypsum might be driven by species-specific germination responses to soil gypsum availability. We analyzed the germination of six gypsum specialists and four closely related generalist plant species from the Iberian Peninsula and the Chihuahuan Desert in four different field soils with contrasting concentrations of gypsum, pH and soil texture. Plant restriction to gypsum was unrelated to the germinating ability of seeds on different substrates. Irrespective of their affinity for gypsum, most species germinated better on mixed gypsum-calcareous soil and worse in the acidic soil treatment. Our data suggest soil pH was the main soil feature driving seed germination, while the effect of gypsum content was generally not significant. The main exception was the Iberian gypsum specialist Helianthemum squamatum (L.) Dum. Cours., which showed increased germination on gypseous soils and higher germination in response to increased soil gypsum content. Except for this species, our findings indicate alkaline soils favor the germination of most of the species analyzed, irrespectively of their gypsum content. HighlightsO_LIGypsum soils are one of the most widespread special substrates of the world C_LIO_LIWe evaluated the effects of natural soils on the germination of gypsum plants C_LIO_LISoil pH was the main soil feature driving seed germination C_LIO_LIThe effect of gypsum content was not significant C_LIO_LIWe suggest a potential origin of gypsophiles from plants adapted to alkaline soils C_LI

ecology↗