Biology subjects

Vargas-Mejia, P.

Publications and source records attributed to Vargas-Mejia, P..

3 recordsLinked to original sources

bioRxiv2025

Phytophthora root rot induces compositional and functional changes in avocado rhizosphere bacterial communities

Understanding how plant pathogens modulate the rhizosphere microbiota is essential to integrated disease management. Here, we assessed the compositional and functional shifts in the avocado rhizosphere bacteriome induced by Phytophthora cinnamomi to elucidate the microbial functions modulated by the infection and identify taxa potentially recruited by the plant as a defense response. Through metabarcoding with metatranscriptomics, we showed that Phytophthora root rot (PRR) induced compositional shifts in bacterial communities, leading to the enrichment of members of MND1, RB41 and Nitrospira. Functional analysis showed that this enrichment may be due to the release of nutrients following root rot, as carbohydrate metabolism was stimulated in rhizobacterial communities of infected trees. We detected evidence of a cry-for-help strategy by the infected plant, as the most active genera in the rhizosphere of PRR-symptomatic trees up-regulated genes associated with stress response and cell signaling, suggesting that they were recruited to mitigate the adverse effects of infection. Our findings highlight the need to combine compositional and functional microbiome data to differentiate between taxa attracted by nutrient release and those actively recruited by the plant. The interactions of the latter with the pathogen should be further studied, as they may constitute promising biocontrol agents.

microbiology↗

bioRxiv2025

Host-Specific Transcriptional Responses of Phytophthora capsici During Early Crown Infection in Cucurbitaceous and Solanaceous Plants

Phytophthora capsici is a destructive, broad-host-range oomycete responsible for substantial losses in global agriculture. While most transcriptomic studies have focused on host responses, the mechanisms by which generalist pathogens dynamically adapt their infection programs to diverse plant species remain poorly understood. Here, we present a comparative transcriptomic analysis of P. capsici during early-stage crown infection in four taxonomically and immunologically distinct hosts, Cucumis sativus, Cucumis melo, Capsicum annuum (CM334), and Solanum lycopersicum, via RNA-seq and multiphoton microscopy. Focusing on crown infections, the natural entry point for the pathogen, we reveal host-specific transcriptional programs that underpin differential infection strategies and outcomes. Our data show that P. capsici exhibits tightly regulated, host-dependent deployment of key virulence factors, including RxLR, NLP, and CRN, and elicitin effectors and reprograms its metabolism to exploit host-specific nutritional environments. In rapidly necrotizing hosts such as tomato, the pathogen induces glycolytic and fatty acid pathways while repressing immunogenic effectors. In contrast, cucurbits support prolonged biotrophic colonization, accompanied by the upregulation of carbohydrate metabolism and membrane transport genes. In the partially resistant chili pepper CM334, P. capsici shows signs of metabolic stress, cell wall remodeling, and effector repression, which is consistent with failed invasion. Functional validation via RNAi-mediated silencing of selected effectors revealed distinct roles in modulating virulence and host necrosis, confirming the functional relevance of the transcriptomic profiles. Co-expression network analysis uncovered discrete transcriptional modules associated with tissue-specific colonization, nutrient acquisition, and immune evasion. These results reveal how a generalist soil-borne pathogen finely tunes its gene expression in response to host-specific constraints, revealing conserved and host-specific transcriptional strategies that drive infection success or failure. This work provides mechanistic insight into adaptive virulence and expands our understanding of host-pathogen compatibility in eukaryotic microbes.

molecular biology↗

bioRxiv2022

Differential RNA-silencing and plasmodesmata callose deposition in leaves and stems of transgenic tobacco plants during Tobacco etch virus infection recovery

Viruses are amongst the most prevalent pathogens that threaten plants. Plants have evolved a sequence-specific defense mechanism against viruses to ensure survival, known as RNA silencing, which includes transcriptional and post-transcriptional gene silencing. After a viral infection, some plants undergo recovery and become further resistant to viral infection. To identify additional mechanisms underlying disease recovery besides the known RNA silencing, we analyzed transgenic tobacco plants expressing a transcript derived from the Nuclear Inclusion "a" protein (NIa) cistron of the tobacco etch virus (TEV), which had recovered from infection three weeks following viral inoculation. Using in situ hybridizations and qRT-PCR, we detected the viral RNA and the transgene-derived transcript in stem sections adjacent to the recovered leaves. To further characterize the silenced and non-silenced conditions, we undertook tissue-specific RNA-Seq and small RNA-Seq analyses in leaf and stem. We found more differentially expressed genes (DEGs) in the recovered leaf, primarily related to defense, silencing, and hormone signaling responses. Finally, we observed differences in plasmodesmata callose deposition and callose-related genes. Overall, our findings suggest that cell-to-cell viral restriction movement also participates in the recovery of TEV infection in transgenic tobacco plants, besides the key function of RNA silencing.

plant biology↗