Biology subjects

Tejomurthula, S.

Publications and source records attributed to Tejomurthula, S..

3 recordsLinked to original sources

bioRxiv2023

Comparative transcriptomics provides insight into molecular mechanisms of zinc tolerance in the ectomycorrhizal fungus Suillus luteus

Zinc is a major soil contaminant and high zinc levels can disrupt growth, survival, and reproduction of fungi. Some fungal species have evolved zinc tolerance through cell processes mitigating zinc toxicity, though the genes and detailed mechanisms underlying fungal zinc tolerance remain unexplored. To fill this gap in knowledge, we investigated the gene expression of zinc tolerance in the mycorrhizal fungus Suillus luteus. We found that zinc tolerance in this species is both a constitutive and environmentally dependent trait. Highly differentially expressed genes were predicted to be involved in transmembrane transport, metal chelation, oxidoreductase activity, and signal transduction. Some of these genes were previously reported as candidates for S. luteus zinc tolerance, while others are reported here for the first time. Overall, we found S. luteus zinc tolerance is associated with differences in expression of genes involved in metal exclusion and immobilization, as well as recognition and mitigation of metal-induced oxidative stress. Our results contribute to understanding the mechanisms of fungal metal tolerance and pave the way for further research on the role of metal tolerance in mycorrhizal associations.

genomics↗

bioRxiv2023

Phylogeny, morphology, virulence, ecology, and host range of Ordospora pajunii (Ordosporidae),a microsporidian symbiont of Daphnia spp.

Impacts of microsporidia on host individuals are frequently subtle and can be context dependent. A key example of the latter comes from a recently discovered microsporidian symbiont of Daphnia, the net impact of which was found to shift from negative to positive based on environmental context. Given this, we hypothesized low baseline virulence of the microsporidian; here, we investigated the impact of infection on hosts in controlled conditions and the absence of other stressors. We also investigated its phylogenetic position, ecology and host range. The genetic data indicates that the symbiont is Ordospora pajunii, a newly described microsporidian parasite of Daphnia. We show that O. pajunii infection damages the gut, causing infected epithelial cells to lose microvilli and then rupture. The prevalence of this microsporidian could be high (up to 100% in the lab and 77% of adults in the field). Its overall virulence was low in most cases, but some genotypes suffered reduced survival and/or reproduction. Susceptibility and virulence were strongly host-genotype dependent. We found that North American O. pajunii were able to infect multiple Daphnia species, including the European species D. longispina, as well as Ceriodaphnia spp. Given the low, often undetectable virulence of this microsporidian, and potentially far reaching consequences of infections for the host when interacting with other pathogens or food, this Daphnia - O. pajunii symbiosis emerges as a valuable system for studying the mechanisms of context-dependent shifts between mutualism and parasitism, as well as for understanding how symbionts might alter host interactions with resources. ImportanceThe net outcome of symbiosis depends on the costs and benefits to each partner. Those can be context dependent, driving the potential for an interaction to change between parasitism and mutualism. Understanding the baseline fitness impact in an interaction can help us understand those shifts; for an organism that is generally parasitic, it should be easier for it to become a mutualist if its baseline virulence is relatively low. Recently, a microsporidian was found to become beneficial to its Daphnia hosts in certain ecological contexts, but little was known about the symbiont (including its species identity). Here, we identify it as the microsporidium Ordospora pajunii. Despite the parasitic nature of microsporidia, we found O. pajunii to be, at most, mildly virulent; this helps explain why it can shift towards mutualism in certain ecological contexts and helps establish O. pajunii is a valuable model for investigating shifts along the mutualism-parasitism continuum.

ecology↗

bioRxiv2022

Stepwise recombination suppression around the mating-type locus in the fungus Schizothecium tetrasporum (Ascomycota, Sordariales)

Recombination is often suppressed at sex-determining loci in plants and animals, and at self-incompatibility or mating-type loci in plants and fungi. In fungal ascomycetes, recombination suppression around the mating-type locus is associated with pseudo-homothallism, i.e., the production of self-fertile dikaryotic sexual spores carrying the two opposite mating types. This has been well studied in two species complexes from different families of Sordariales: Podospora anserina and Neurospora tetrasperma. However, it is unclear whether this intriguing convergent association holds in other species. We show here that Schizothecium tetrasporum, a fungus from a third family in the order Sordariales, also produces mostly self-fertile dikaryotic spores carrying the two opposite mating types. This was due to a high frequency of second meiotic division segregation at the mating-type locus, indicating the occurrence of a single and systematic crossing-over event between the mating-type locus and the centromere, as in P. anserina. The mating-type locus has the typical Sordariales organization, plus a MAT1-1-1 pseudogene in the MAT1-2 haplotype. High-quality genome assemblies of opposite mating types and segregation analyses revealed a suppression of recombination in a region of 1.3 Mb around the mating-type locus. We detected three evolutionary strata, displaying a stepwise extension of recombination suppression, but no rearrangement or transposable element accumulation in the non-recombining region. Our findings indicate a convergent evolution of self-fertile dikaryotic sexual spores across multiple ascomycete fungi. The particular pattern of meiotic segregation at the mating-type locus was associated with recombination suppression around this locus, that had extended stepwise. This association is consistent with a recently proposed mechanism of deleterious allele sheltering through recombination suppression around a permanently heterozygous locus. AUTHOR SUMMARYRecombination allows faster adaptation and the purging of deleterious mutation but is often paradoxically lacking in sex chromosomes. It has been recently recognized that recombination can also be suppressed on fungal mating-type chromosomes, but the evolutionary explanation and the proximal mechanism of this phenomenon remain unclear. By studying here the sexual biology of a poorly studied mold living in rabbit dung, we reveal a striking convergence in three distant fungal lineages of an independently evolved association between the production of self-fertile sexual spores (carrying two nuclei with opposite mating types), a particular segregation of the mating-type locus and the lack of recombination on mating-type chromosomes, having evolved stepwise. Such a convergent association suggests causal relationships and will contribute to unveil the evolutionary causes of recombination suppression. Graphical summary O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=174 SRC="FIGDIR/small/500756v2_ufig1.gif" ALT="Figure 1"> View larger version (40K): org.highwire.dtl.DTLVardef@1cea706org.highwire.dtl.DTLVardef@378c41org.highwire.dtl.DTLVardef@d90297org.highwire.dtl.DTLVardef@1391c74_HPS_FORMAT_FIGEXP M_FIG C_FIG

evolutionary biology↗