Tremblay, V. | bioRxiv Science

bioRxiv2025

A rare recombination allows the redefinition of a major avirulence gene in the Phytophthora sojae genome

Significant yield losses in soybean production are imputable to Phytophthora root and stem rot (PRR) caused by Phytophthora sojae. Soybean resistance to the pathogen depends on the presence of resistance genes (Rps) that recognize key effectors from P. sojae, which are encoded by avirulence genes (Avr). A unique molecular signature associated with these genes allows the prediction of the outcome of infection with great accuracy making the interaction Rps-Avr central to reduce disease incidence. In this study, we reassessed the identity of the avirulence gene whose protein product is recognized by Rps6. Following extensive soil sampling and single-spore isolation of a large population of P. sojae, we found two salient isolates carrying a rare recombination between two effectors, Avr3c and Avr4/6. Using a PCR assay and molecular markers, we showed that only alleles at the Avr3c locus were in perfect association with the phenotypes of the isolates. Furthermore, whole-genome resequencing and de novo assembly of the two isolates revealed the full extent of this genomic rearrangement. These results bring to light an unsuspected connection between Avr3c and Rps6 and offer a more reliable target for the pathotyping of P. sojae, which ultimately leads to a better use of resistant soybean material.

plant biology↗

bioRxiv2021

The immediate early protein 1 of the human herpesvirus 6B counteracts NBS1 and prevents homologous recombination repair pathways

Viral infection often trigger an ATM-dependent DNA damage response (DDR) in host cells that suppresses viral replication. To counteract this antiviral surveillance system, viruses evolved different strategies to induce the degradation of the MRE11/RAD50/NBS1 (MRN) complex and prevent subsequent DDR signaling. Here, we report that human herpesvirus 6B (HHV-6B) infection causes genomic instability by suppressing the host cells ability to induce ATM-dependent signaling pathways. Expression of immediate early protein 1 (IE1) phenocopies this phenotype and blocks further homology-directed double-strand break (DSB) repair. In contrast to other viruses, IE1 does not affect the stability of the MRN complex. Instead, it uses two distinct domains to inhibit ATM serine/threonine kinase (ATM) activation at DSBs. Structure-based analyses revealed that the N-terminal domain of IE1 interacts with the BRCA1 C-terminal domain 2 of nibrin (NBN, also known as NBS1), while ATM inhibition is attributable to on its C-terminal domain. Consistent with the role of the MRN complex in antiviral responses, NBS1 depletion resulted in increased HHV-6B replication in infected cells. However, in semi-permissive cells, viral integration of HHV-6B into the telomeres was not strictly dependent on NBS1, supporting models where this process occurs via telomere elongation rather than through DNA repair. Interestingly, as IE1 expression has been detected in cells of subjects with inherited chromosomally-integrated form of HHV-6B (iciHHV-6B), a condition associated with several health conditions, our results raise the possibility of a link between genomic instability and the development of iciHHV-6-associated diseases. Significance StatementMany viruses have evolved ways to inhibit DNA damage signaling, presumably to prevent infected cells from activating an antiviral response. Here, we show that this is also true for human herpesvirus 6B (HHV-6B), through its immediate early protein 1 (IE1). However, in contrast to adenovirus immediate early proteins, HHV-6B IE1 is recruited to double-strand breaks in an NBS1-dependent manner and inhibits ATM serine/threonine kinase activation. Characterizing this phenotype revealed a unique mechanism by which HHV-6B manipulates DNA damage signaling in infected cells. Consistently, viral replication is restricted by the MRN complex in HHV-6B infected cells. Viral integration of HHV-6B into the hosts telomeres is not strictly dependent on NBS1, challenging current models where integration occurs through homology-directed repair.

microbiology↗

bioRxiv2020

Global prevalence of potentially pathogenic short-tandem repeats in an epilepsy cohort

This study aims to decipher the role of short tandem repeats (STRs) in epilepsy patients. Whole genome short-read sequencing data of 734 epileptic patients was used to look for known STR expansions associated with increased risk of neurodevelopmental diseases or epilepsy using three different software. Results show one hit of particular interest on ARX gene associated with Early Infantile Encephalopathic Epilepsy that could be causal for one patient with developmental and epileptic encephalopathy. However, we show that the different software do not agree on most of the calls above the threshold and that experimental validation is still needed for diagnostic, although these algorithms could prove useful for pre-selection of samples to be validated.

genetics↗