Biology subjects

Deng, C. H.

Publications and source records attributed to Deng, C. H..

6 recordsLinked to original sources

bioRxiv2025

TESS: A Forward Simulation Framework for Studying the Role of Transposable Elements in Genome Expansion and Contraction

Genome expansion and contraction are reportedly driven by transposable element (TE) activity, but the underlying dynamics remain enigmatic due to a lack of historical records tracing these changes. Here, we present PrinTE for versatile, forward-time simulation of whole-genome sequences with highly customizable transposon dynamics. Through simulations, we confirm that the distribution of TE sequence divergence reflects their historical insertion and deletion dynamics, which can be used to infer TE dynamic parameters through PrinTE simulations. We analyzed the pangenome of Pucciniomycotina, a subdivision of fungi containing myrtle rust (Austropuccinia psidii), which drastically expanded its genome size to 1018 Mb. Our analyses reveal that the best strategy for controlling genome size is to avoid the invasion of LTR retrotransposons (LTR-RTs). While illegitimate recombination (IR) is considered the most effective counteraction of LTR-RT invasions leaving only solo LTR remnants, we observed a strong positive correlation between solo:intact LTR ratio (strength of LTR-RT removal) and genome size (r = 0.65), and a near-linear correlation between solo LTR count and genome size (r = 0.98). This result suggests that IR alone may not effectively prevent genome obesity. Through simulation of Pucciniomycotina genomes, we proposed that A. psidii might experience a prolonged period of genome expansion followed by a short, potent, and likely ongoing period of contraction. PrinTE is freely available at https://github.com/cwb14/PrinTE.git.

bioinformatics↗

bioRxiv2020

Long read assembly of the pandemic strain of Austropuccinia psidii (myrtle rust) reveals an unusually large (gigabase sized) and repetitive fungal genome.

Austropuccinia psidii, originating in South America, is a globally invasive fungal plant pathogen that causes rust disease on Myrtaceae. Several biotypes are recognized, with the most widely distributed pandemic biotype spreading throughout the Asia-Pacific and Oceania regions over the last decade. Austropuccinia psidii has a broad host range with more than 480 myrtaceous species. Since first detected in Australia in 2010, the pathogen has caused the near extinction of at least three species and negatively affected commercial production of several Myrtaceae. To enable molecular and evolutionary studies into A. psidii pathogenicity, we assembled a highly contiguous genome for the pandemic biotype. With an estimated haploid genome size of just over 1 Gb (gigabases), it is the largest assembled fungal genome to date. The genome has undergone massive expansion via distinct transposable element (TE) bursts. Over 90% of the genome is covered by TEs predominantly belonging to the Gypsy superfamily. These TE bursts have likely been followed by deamination events of methylated cytosines to silence the repetitive elements. This in turn led to the depletion of CpG sites in transposable elements and a very low overall GC content of 33.8%. The overall gene content is highly conserved, when compared to other closely related Pucciniales, yet the intergenic distances are increased by an order of magnitude indicating a general insertion of TEs between genes. Overall, we show how transposable elements shaped the genome evolution of A. psidii and provide a greatly needed resource for strategic approaches to combat disease spread.

genomics↗

bioRxiv2019

Pyrus Communis chromosome scale assembly

We report an improved assembly and scaffolding of the European pear (Pyrus communis L.) genome (referred to as BartlettDHv2.0), obtained using a combination of Pacific Biosciences RSII Long read sequencing (PacBio), Bionano optical mapping, chromatin interaction capture (Hi-C), and genetic mapping. A total of 496.9 million bases (Mb) corresponding to 97% of the estimated genome size were assembled into 494 scaffolds. Hi-C data and a high-density genetic map allowed us to anchor and orient 87% of the sequence on the 17 chromosomes of the pear genome. About 50% (247 Mb) of the genome consists of repetitive sequences. Comparison with previous assemblies of Pyrus communis and Pyrus x bretschneideri confirmed the presence of 37,445 protein-coding genes, which is 13% fewer than previously predicted.

bioinformatics↗

bioRxiv2019

Pseudo-chromosome length genome assembly of a double haploid ‘Bartlett’ pear (Pyrus communis L.)

We report an improved assembly and scaffolding of the European pear (Pyrus communis L.) genome (referred to as BartlettDHv2.0), obtained using a combination of Pacific Biosciences RSII Long read sequencing (PacBio), Bionano optical mapping, chromatin interaction capture (Hi-C), and genetic mapping. A total of 496.9 million bases (Mb) corresponding to 97% of the estimated genome size were assembled into 494 scaffolds. Hi-C data and a high-density genetic map allowed us to anchor and orient 87% of the sequence on the 17 chromosomes of the pear genome. About 50% (247 Mb) of the genome consists of repetitive sequences. Comparison with previous assemblies of Pyrus communis. and Pyrus x bretschneideri confirmed the presence of 37,445 protein-coding genes, which is 13% fewer than previously predicted.

plant biology↗

bioRxiv2018

Draft Genome Sequence of the Asian Pear Scab Pathogen, Venturia nashicola

Venturia nashicola, which causes scab disease of Asian pear, is a host-specific, biotrophic fungus, with a sexual stage that occurs during saprobic growth. V. nashicola is endemic to Asia and is regarded as a quarantine threat to Asian pear production outside of this continent. Currently, fungicide applications are routinely used to control scab disease. However, fungicide resistance in V. nashicola, as in other fungal pathogens, is an ongoing challenge and alternative control or prevention measures that include, for example, the deployment of durable host resistance, are required. A close relative of V. nashicola, V. pirina, causes scab disease of European pear. European pear displays non-host resistance (NHR) to V. nashicola and Asian pears are non-hosts of V. pirina. It is anticipated that the host specificity of these two fungi is governed by differences in their effector arsenals, with a subset responsible for activating NHR. The Pyrus-Venturia pathosystems provide a unique opportunity to dissect the underlying genetics of non-host interactions and to understand coevolution in relation to this potentially more durable form of resistance. Here, we present the first V. nashicola draft whole genome sequence (WGS), which is made up of 40,800 scaffolds (totalling 45 Mb) and 11,094 predicted genes. Of these genes, 1,232 are predicted to encode a secreted protein by SignalP, with 273 of these predicted to be effectors by EffectorP. The V. nashicola WGS will enable comparison to the WGSs of other Venturia spp. to identify effectors that potentially activate NHR in the pear scab pathosystems.

genomics↗

bioRxiv2017

Specific hypersensitive response-associated recognition of new apoplastic effectors from Cladosporium fulvum in wild tomato

Tomato leaf mould disease is caused by the biotrophic fungus Cladosporium fulvum. During infection, C. fulvum produces extracellular small secreted protein (SSP) effectors that function to promote colonization of the leaf apoplast. Resistance to the disease is governed by Cf immune receptor genes that encode receptor-like proteins (RLPs). These RLPs recognize specific SSP effectors to initiate a hypersensitive response (HR) that renders the pathogen avirulent. C. fulvum strains capable of overcoming one or more of all cloned Cf genes have now emerged. To combat these strains, new Cf genes are required. An effectoromics approach was employed to identify wild tomato accessions carrying new Cf genes. Proteomics and transcriptome sequencing were first used to identify 70 apoplastic in planta-induced C. fulvum SSPs. Based on sequence homology, 61 of these SSPs were novel or lacked known functional domains. Seven, however, had predicted structural homology to antimicrobial proteins, suggesting a possible role in mediating antagonistic microbe-microbe interactions in planta. Wild tomato accessions were then screened for HR-associated recognition of 41 SSPs using the Potato virus X-based transient expression system. Nine SSPs were recognized by one or more accessions, suggesting that these plants carry new Cf genes available for incorporation into cultivated tomato.

microbiology↗