Pedro Gómez

Insect-associated microbiomes constitute a crucial component of the physiological fitness of insects. Thus, the structure and composition of the bacterial community may have important implications for the performance of insect pest vectors, and in turn, for plant crops. However, the relative effects of the transition between host plants and feeding on virus-infected plants remain unclear. In this study, we examined the bacterial community structure and composition of the cotton-melon aphid, Aphis gossypii Glover, in response to transitions between cucurbit plant species and melon plants infected by persistent (cucurbit aphid-borne yellows virus, CABYV) and nonpersistent (watermelon mosaic virus, WMV) plant viruses in single and mixed infections. Our 16S rRNA gene sequencing analysis revealed that bacterial diversity was greater in aphids feeding on melon than those feeding on cucumber, and re-established when returned to melon. This microbiome structure alteration was mainly caused by shifts in the relative abundance of facultative symbionts, such as Arsenophonus and Sphingomonas. Furthermore, viral infections significantly reduced microbiome diversity compared with that in healthy plants, with the lowest diversity observed in aphids feeding on mixed-infection plants with cucurbit aphid-borne yellows virus and watermelon mosaic virus. A notable negative correlation between Buchnera and Arsenophonus abundance was identified and validated by quantitative polymerase chain reaction in those viruliferous aphids, suggesting a compensatory mechanism and that viral infections may modulate endosymbiont interactions. This study underlines shifts in the aphid microbiome, which could provide insights for further investigation of microbial resource-based solutions to control aphid pests and associated viral diseases in agriculture. [ ] Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY 4.0 International license .

Plants respond to biotic and abiotic factors through specific physiological and metabolic changes that optimize their survival. However, the extent to which the combination of both stressors could modulate common or exclusive signaling pathways remains unclear, as most studies on gene-specific plant expression focus on a single stress. In this study, we examined the gene expression patterns in two cucurbit species, melon and zucchini, each with high- and low-temperature-tolerant cultivars, under watermelon mosaic virus (WMV) infection and three temperature ranges (20/14, 26/20, and 32/24 °C). Our results showed that WMV accumulation was higher in zucchini than in melon plants and was influenced by both thermotolerance and temperature conditions. Comparative 3′ mRNA-seq analysis revealed that zucchini exhibited a 2.6-fold higher percentage of differentially expressed genes (DEGs) than melon, with the highest percentage of DEGs occurring at lower temperatures in the thermosusceptible plants of both species, possibly associated with greater WMV accumulation. Notably, the greatest number of unique DEGs was detected in high-temperature and WMV-infected plants of thermotolerant melon (711 DEGs) and thermosusceptible zucchini (306 DEGs). Among the top 15 Gene Ontology terms, four orthologous genes were identified, three of which—MELO3C023308, MELO3C024920, and Cp4.1LG05g12560—exhibited a significant temperature-dependent expression under WMV infection, and potentially encode an F-box protein, a metal ion transporter, and a photomorphogenesis-related factor, respectively. These findings provide novel insights into plant–virus–environment interactions and may contribute to enhancing cucurbit crop resilience and food security.

Mixed infections of plant viruses are common in crops and represent a critical biotic factor with substantial epidemiological implications for plant viral diseases. Compared to single-virus infections, mixed infections arise from simultaneous or sequential infections, which can inevitably affect the ecology and evolution of the diseases. These infections can either exacerbate or ameliorate symptom severity, including virus–virus interactions within the same host that may influence a range of viral traits associated with disease emergence. This underscores the need for a more comprehensive understanding of how the order of virus arrival to the host can impact plant disease dynamics. From this perspective, we reviewed the current evidence regarding the impact of mixed infections within the framework of simultaneous and sequential infections in plants, considering the mode of viral transmission. We also examined how the temporal order of mixed infections could affect the dynamics of viral populations and present a case study of two aphid-transmitted viruses infecting melon plants, suggesting that the order of virus arrival significantly affects viral load and disease outcomes. Finally, we anticipate future research that reconciles molecular epidemiology and evolutionary ecology, underlining the importance of biotic interactions in shaping viral epidemiology and plant disease dynamics in agroecosystems.

El texto realiza un recorrido por la historia de los archivos y archiveros de Castilla y León desde la perspectiva del autor. Describe sus experiencias en las distintas provincias, el desarrollo del sistema archivístico en la región y las relaciones de colaboración. The text takes a journey through the history of the archives and archivists of Castilla y León from the author's perspective. It describes their experiences in the different provinces, the development of the archival system in the region and the collaborative relationships.

Biotic and abiotic environmental factors shape plant responses. As such the interplay between viral infection and heat-stress can trigger specific physiological and metabolic plant responses that lead to gene-specific changes in defense and development. However, although plant gene expression patterns have been thoroughly studied under a single stress, the extent to which the combination of both stressors could modulate common or exclusive signaling pathways remains unclear. In this study, we examined the effects of watermelon mosaic virus infection and diurnal temperature variations (20/14 °C, 26/20 °C, and 32/24 °C) on the gene responses of two plant species (melon and zucchini), each with high- and low-temperature tolerance, using a differential 3’mRNA-seq approach. The WMV load was much greater in zucchini than in melon plants, and was also dependent on the temperature conditions and tolerance of each plant species. Our comparative RNA-seq analysis revealed that the percentage of differentially expressed genes (DEGs) was higher in the thermo-susceptible plants of both species under the combination of WMV infection and low temperatures (20 °C). Among these significantly regulated genes, between 37 % and 45 % were related to biotic and/or abiotic stress. Furthermore, we found that 30 GO terms were involved in the response to both combined stress from low temperatures and 23 GO terms for high temperatures, which were exclusive to the thermotolerant varieties. Together, these findings allowed the identification of two unique orthologous genes linked to temperature and virus infection in melon and zucchini plants. Understanding the effects of biotic and abiotic factors on plant responses is essential for unraveling the complexity of plant-pathogen-environment interactions and developing strategies to enhance plant resilience and productivity under changing climatic conditions.

Mixed viral infections occur frequently in plants, leading to diseases that can be difficult to diagnose, especially when an unknown virus is hidden behind expression of symptoms common to other viruses. We monitored aphid‐ and whitefly‐transmitted viruses in two cucurbit crops (melon and watermelon) for three consecutive seasons (2021–2023) across three production regions in Spain, focusing on the common yellowing and mosaic symptoms. A total of 984 symptomatic leaf samples from 246 field plots were tested for 10 frequently found cucurbit viruses. Cucurbit aphid‐borne yellows virus (CABYV) was the most prevalent virus infecting both cucurbit crops over the three seasons. Additionally, occurrence of watermelon mosaic virus (WMV) in samples with mosaic symptoms was significant. However, an important proportion of yellowing symptomatic samples tested negative for known viruses. Using a sequence‐independent approach, we identified a novel polerovirus, Pepo aphid‐borne yellows virus (PABYV), which was widespread, infecting both crops. Analysis of our long‐term cucurbit frozen‐sample collection revealed that PABYV had emerged in Spain in 2018, possibly unnoticed as its yellowing symptoms were similar to CABYV, with which it was frequently associated. Additionally, we found the cryptic Cucumis melo endornavirus (CmEV) in all tested melon samples from 2011 and, for the first time, in pumpkin. Genetic characterization of CABYV, PABYV and CmEV populations revealed a replacement of ancient CABYV isolates by contemporary ones, while PABYV and CmEV isolates were genetically homogenous among their populations. This study underlines the need for continuous surveillance and further investigation into common symptoms of mixed viral infections.

Pepino mosaic virus (PepMV) causes significant economic losses in tomato crops worldwide. Since its first detection infecting tomato in 1999, aggressive PepMV variants have emerged. This study aimed to characterize two aggressive PepMV isolates, PepMV-H30 and PepMV-KLP2. Both isolates were identified in South-Eastern Spain infecting tomato plants, which showed severe symptoms, including bright yellow mosaics. Full-length infectious clones were generated, and phylogenetic relationships were inferred using their nucleotide sequences and another 35 full-length sequences from isolates representing the five known PepMV strains. Our analysis revealed that PepMV-H30 and PepMV-KLP2 belong to the EU and CH2 strains, respectively. Amino acid sequence comparisons between these and mild isolates identified 8 and 15 amino acid substitutions for PepMV-H30 and PepMV-KLP2, respectively, potentially involved in severe symptom induction. None of the substitutions identified in PepMV-H30 have previously been described as symptom determinants. The E236K substitution, originally present in the PepMV-H30 CP, was introduced into a mild PepMV-EU isolate, resulting in a virus that causes symptoms similar to those induced by the parental PepMV-H30 in Nicotiana benthamiana plants. In silico analyses revealed that this residue is located at the C-terminus of the CP and is solvent-accessible, suggesting its potential involvement in CP–host protein interactions. We also examined the subcellular localization of PepGFPm2^E236K in comparison to that of PepGFPm2, focusing on chloroplast affection, but no differences were observed in the GFP subcellular distribution between the two viruses in epidermal cells of N. benthamiana plants. Due to the easily visible symptoms that PepMV-H30 and PepMV-KLP2 induce, these isolates represent valuable tools in programs designed to breed resistance to PepMV in tomato.

Pepino mosaic virus (PepMV) causes significant economic losses in tomato crops worldwide. Since its first detection infecting tomato in 1999, aggressive PepMV variants have emerged. This study aimed to characterize two aggressive PepMV isolates, PepMV-H30 and PepMV-KLP2. Both isolates were identified in South-Eastern Spain infecting tomato plants, which showed severe symptoms, including bright yellow mosaics. Full-length infectious clones were generated, and phylogenetic relationships were inferred using their nucleotide sequences and another 35 full-length sequences from isolates representing the five PepMV known strains. Our analysis revealed that PepMV-H30 and PepMV-KLP2 belong to the EU and CH2 strains, respectively. Amino acid sequence comparisons between these and mild isolates identified 8 and 15 amino acid substitutions for PepMV-H30 and PepMV-KLP2, respectively, potentially involved in severe symptom induction. None of the substitutions identified in PepMV-H30 had previously been described as symptom determinant. The E236K substitution, originally present in the PepMV-H30 CP, was introduced into a mild PepMV-EU isolate, resulting in a virus that causes symptoms similar to those induced by the parental PepMV-H30. In silico analyses revealed that this residue is located at the C-terminus of the CP and is solvent-accessible, suggesting its potential involvement in CP-host proteins interactions. We also examined the subcellular localization of PepGFPm2E236K in comparison to that of PepGFPm2, focusing on chloroplast affection, but no differences were observed in the GFP subcellular distribution between the two viruses. Due to the easily visible symptoms that PepMV-H30 and PepMV-KLP2 induce, these isolates represent valuable tools in programs destined to breeding resistance to PepMV in tomato.

Understanding the emergence and prevalence of viral diseases in crops requires the systematic epidemiological monitoring of viruses, as well as the analysis of how ecological and evolutionary processes combine to shape viral population dynamics. Here, we extensively monitored the occurrence of six aphid-transmitted viruses in melon and zucchini crops in Spain for 10 consecutive cropping seasons between 2011 and 2020. The most prevalent viruses were cucurbit aphid-borne yellows virus (CABYV) and watermelon mosaic virus (WMV), found in 31 and 26% of samples with yellowing and mosaic symptoms. Other viruses, such as zucchini yellow mosaic virus, cucumber mosaic virus, Moroccan watermelon mosaic virus, and papaya ring spot virus, were detected less frequently (<3%) and mostly in mixed infections. Notably, our statistical analysis showed a significant association between CABYV and WMV in melon and zucchini hosts, suggesting that mixed infections might be influencing the evolutionary epidemiology of these viral diseases. We then carried out a comprehensive genetic characterization of the full-length genome sequences from CABYV and WMV isolates by using the Pacific Biosciences single-molecule real-time (PacBio) high-throughput technology to assess the genetic variation and structure of their populations. Our results showed that the CABYV population displayed seven codons under positive selection, and although most isolates clustered in the Mediterranean clade, a subsequent analysis of molecular variance revealed a significant, fine-scale temporal structure, which was in part explained by the level of the variance between isolates from single and mixed infections. In contrast, the WMV population genetic analysis showed that most of the isolates grouped into the Emergent clade, with no genetic differentiation and under purifying selection. These results underlie the epidemiological relevance of mixed infections for CABYV and provide a link between genetic diversity and CABYV dynamics at the whole-genome level.