Characterization of a novel polyextremotolerant fungus, \u3ci\u3eExophiala viscosa\u3c/i\u3e, with insights into its melanin regulation and ecological niche

Black yeasts are polyextremotolerant fungi that contain high amounts of melanin in their cell wall and maintain a primar yeast form. These fungi grow in xeric, nutrient depletes environments which implies that they require highly flexible metabolisms and have been suggested to contain the ability to form lichen-like mutualisms with nearby algae and bacteria. However, the exact ecological niche and interactions between these fungi and their surrounding community are not well understood. We have isolated 2 novel black yeasts from the genus Exophiala that were recovered from dryland biological soil crusts. Despite notable differences in colony and cellular morphology, both fungi appear to be members of the same species, which has been named Exophiala viscosa (i.e. E. viscosa JF 03-3 Goopy and E. viscosa JF 03-4F Slimy). A combination of whole genome sequencing, phenotypic experiments, and melanin regulation experiments have been performed on these isolates to fully characterize these fungi and help decipher their fundamental niche within the biological soil crust consortium. Our results reveal that E. viscosa is capable of utilizing a wide variety of carbon and nitrogen sources potentially derived from symbiotic microbes, can withstand many forms of abiotic stresses, and excretes melanin which can potentially provide ultraviolet resistance to the biological soil crust community. Besides the identification of a novel species within the genus Exophiala, our study also provides new insight into the regulation of melanin production in polyextremotolerant fungi

The transcriptional activator ClrB is crucial for the degradation of soybean hulls and guar gum in Aspergillus niger

Low-cost plant substrates, such as soybean hulls, are used for various industrial applications. Filamentous fungi are important producers of Carbohydrate Active enZymes (CAZymes) required for the degradation of these plant biomass substrates. CAZyme production is tightly regulated by several transcriptional activators and repressors. One such transcriptional activator is CLR-2/ClrB/ManR, which has been identified as a regulator of cellulase and mannanase production in several fungi. However, the regulatory network governing the expression of cellulase and mannanase encoding genes has been reported to differ between fungal species. Previous studies showed that Aspergillus niger ClrB is involved in the regulation of (hemi-)cellulose degradation, although its regulon has not yet been identified. To reveal its regulon, we cultivated an A. niger ΔclrB mutant and control strain on guar gum (a galactomannan-rich substrate) and soybean hulls (containing galactomannan, xylan, xyloglucan, pectin and cellulose) to identify the genes that are regulated by ClrB. Gene expression data and growth profiling showed that ClrB is indispensable for growth on cellulose and galactomannan and highly contributes to growth on xyloglucan in this fungus. Therefore, we show that A. niger ClrB is crucial for the utilization of guar gum and the agricultural substrate, soybean hulls. Moreover, we show that mannobiose is most likely the physiological inducer of ClrB in A. niger and not cellobiose, which is considered to be the inducer of N. crassa CLR-2 and A. nidulans ClrB

Unraveling the regulation of sugar beet pulp utilization in the industrially relevant fungus Aspergillus niger

Efficient utilization of agro-industrial waste, such as sugar beet pulp, is crucial for the bio-based economy. The fungus Aspergillus niger possesses a wide array of enzymes that degrade complex plant biomass substrates, and several regulators have been reported to play a role in their production. The role of the regulators GaaR, AraR, and RhaR in sugar beet pectin degradation has previously been reported. However, genetic regulation of the degradation of sugar beet pulp has not been assessed in detail. In this study, we generated a set of single and combinatorial deletion mutants targeting the pectinolytic regulators GaaR, AraR, RhaR, and GalX as well as the (hemi-)cellulolytic regulators XlnR and ClrB to address their relative contribution to the utilization of sugar beet pulp. We show that A. niger has a flexible regulatory network, adapting to the utilization of (hemi-)cellulose at early timepoints when pectin degradation is impaired

Ocean current patterns drive the worldwide colonization of eelgrass (Zostera marina)

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Ocean current patterns drive the worldwide colonization of eelgrass (Zostera marina)

DATA AVAILABILITY : Genome data have been deposited in Genbank (short read archive, Supplementary Data Table 3). Coding sequences of Z. japonica and Z. marina for the ASTRAL analysis can be found on figshare (https://doi.org/10.6084/m9.figshare.21626327.v1). VCF files of the 11,705 core SNPs can be accessed at https://doi.org/10.6084/m9.figshare.21629471.v1. Source data for Fig. 1b,c are given, as well as statistics of sequencing coverage, mapping rate and further specifications of each sequenced library (Supplementary Tables 1–3). Source data are provided with this paper.CODE AVAILABILITY : Custom-made scripts are deposited on GitHub for SNP filtering (github.com/leiyu37/populationGenomics_ZM.git), for clone mate detection (github.com/leiyu37/Detecting-clonemates.git), for heterozygote and nucleotide diversity quantification (github.com/leiyu37/populationGenomics_ZM.git) and to prepare SplitsTree input files (https://github.com/leiyu37/populationGenomics_ZM/blob/main/10_SplitsTree/vcf2alignment.py) and SNAPP input files (github.com/mmatschiner/snapp_prep). Scripts for calculating D-statistics are available at github.com/mmatschiner/tutorials/blob/master/analysis_of_introgression_with_snp_data/src/plot_d.rb. Scripts to prepare the gene presence/absence analysis are deposited on https://github.com/leiyu37/populationGenomics_ZM/tree/main/gene_presense_absence_analysis. Further software code for the MSMC analysis are found at http://lh3lh3.users.sourceforge.net/snpable.shtml (generation of mappability mask file for each of six chromosomes using SNPable) and at https://github.com/stschiff/msmc-tools (generation of ramet-specific mask file based on a bam file using bamCaller.py).SUPPLEMENTARY MATERIAL : Supplementary Notes 1–8, Tables 1–6 and Figs. 1–12.SUPPLEMENTARY DATA : Table 1: Sequence coverage. Supplementary Data Table 2: Mapping rate. Supplementary Data Table 3: Accession number of each library.SOURCE DATA : Fig. 1b,c.Currents are unique drivers of oceanic phylogeography and thus determine the distribution of marine coastal species, along with past glaciations and sea-level changes. Here we reconstruct the worldwide colonization history of eelgrass (Zostera marina L.), the most widely distributed marine flowering plant or seagrass from its origin in the Northwest Pacific, based on nuclear and chloroplast genomes. We identified two divergent Pacific clades with evidence for admixture along the East Pacific coast. Two west-to-east (trans-Pacific) colonization events support the key role of the North Pacific Current. Time-calibrated nuclear and chloroplast phylogenies yielded concordant estimates of the arrival of Z. marina in the Atlantic through the Canadian Arctic, suggesting that eelgrass-based ecosystems, hotspots of biodiversity and carbon sequestration, have only been present there for ~243 ky (thousand years). Mediterranean populations were founded ~44 kya, while extant distributions along western and eastern Atlantic shores were founded at the end of the Last Glacial Maximum (~19 kya), with at least one major refuge being the North Carolina region. The recent colonization and five- to sevenfold lower genomic diversity of the Atlantic compared to the Pacific populations raises concern and opportunity about how Atlantic eelgrass might respond to rapidly warming coastal oceans.Open access funding provided by GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel. The China Scholarship Council, the Helmholtz School for Marine Data Science, the US Department of Energy Joint Genome Institute Community Sequencing Program, the Office of Science of the US Department of Energy and the National Science Foundation.http://www.nature.com/nplantshj2024BiochemistryGeneticsMicrobiology and Plant PathologyLife below wate

The yeast-one-hybrid assay identifies LHCA2 and HSPRO2 as double-SORLIP1 element binding proteins in Arabidopsis thaliana

Early light induced proteins (ELIPs) are widely distributed in the plant kingdom. Members of the extended light harvesting complex (LHC) superfamily, ELIPs are expressed in the nucleus and the ELIP protein is transiently localized to the thylakoid membranes. Significant increase in expression of ELIPs has been reported in response to stresses such as high light, high and low temperature, exposure to UV and salinity. ELIP expression also increases at transitional stages of chloroplast development such as deetiolation, conversion to chromoplast, and senescence. In search of cis-regulatory regions, the A. thaliana ELIP1 gene promoter has been investigated in our lab. A double-SORLIP1 element was identified as a critical cis-regulatory region common in the promoters of A. thaliana ELIP1 (At3g22840) and ELIP2 (At4g14690). Point mutations in the double-SORLIP1 element led to significant decline in expression. Due to the importance of the double-SORLIP1 element, a yeast-one-hybrid assay was set up to find the specific DNA-binding proteins that bind to this region. Light harvesting complex II (LHCA2) and the ortholog of sugar beet HS1 PRO-1 2, heat-shock-like protein 2 (HSPRO2), showed a high specificity in binding to the double-SORLIP1 element. Investigation of lhca2 and hspro2 Arabidopsis mutants did not show any significant difference in high light induced expression of ELIP1 or ELIP2 as compared to wild type. However, the high frequency of LHCA2 clones selected by yeast-one-hybrid assay and the high specificity in binding to the double-SORLIP1 element cannot be ignored. After reviewing the literature, I hypothesized that LHCA2 may be a new retrograde signal that regulates expression of ELIP genes. However, more experimental evidence is needed to support this proposed function. The potential regulatory role of HSPRO2 is also discussed

The <i>HAC1</i> Histone Acetyltransferase Promotes Leaf Senescence via Regulation of <i>ERF022</i>

AbstractNutrient remobilization during leaf senescence nourishes the growing plant. Understanding the regulation of this process is essential for reducing our dependence on nitrogen fertilizers and increasing agricultural sustainability. Our lab is interested in chromatin changes that accompany the transition to leaf senescence. Previously, darker green leaves were reported for Arabidopsis thaliana hac1 mutants, defective in a gene encoding a histone acetyltransferase in the CREB-binding protein family. Here, we show that two Arabidopsis hac1 alleles display delayed age-related developmental senescence, but have normal dark-induced senescence. Using a combination of ChIP-seq for H3K9ac and RNA-seq for gene expression, we identified 44 potential HAC1 targets during age-related developmental senescence. Genetic analysis demonstrated that one of these potential targets, ERF022, is a positive regulator of leaf senescence. ERF022 is regulated additively by HAC1 and MED25, suggesting MED25 recruits HAC1 to the ERF022 promoter to increase its expression in older leaves.</jats:p