Biology subjects

Pozo, M. J.

Publications and source records attributed to Pozo, M. J..

6 recordsLinked to original sources

bioRxiv2026

Vicariance and dispersal shape the colonization history of the Galapagos carpenter bee, Xylocopa darwini

Island colonization and subsequent diversification are often shaped by a complex interplay between organism-specific traits including dispersal capacity and ecological requirements, and the configuration of the landscape over geological time. Here, we investigate the evolutionary history and population genomics of the Galapagos carpenter bee, Xylocopa darwini, across six islands of the Galapagos archipelago. Despite the bees presumed strong flight ability, we find evidence of long-term isolation among all islands with the strongest divergence occurring between the eastern and western islands, and no evidence of contemporary gene flow between any island pairs. Our analyses indicate that the initial colonization of the archipelago by X. darwini occurred during the early Pleistocene, a period when most current islands except for the youngest islands of Isabela and Fernandina, were subaerial, and part of a large contiguous paleo-landmass. Diversification across the Galapagos islands closely tracks the timing of geological separation of the islands, with carpenter bees from the oldest eastern islands splitting first from the western clade over a million years ago. Subsequent diversification of the western clade tracks the sequential fragmentation of the western, central, and southern islands (Isabela, Santiago, Santa Cruz, and Floreana), rather than the geological age of the islands. Despite being on the oldest island, the bee population on Espanola appears to have been founded more recently (within the last 100,000 years) from San Cristobal, providing an exception to diversification tracking paleogeography and is the only example of founding via over-water dispersal among the sampled island populations. Measures of contemporary genetic diversity and runs of homozygosity (ROHs) suggest substantially smaller current population sizes on the southern island of Floreana and the eastern islands of Espanola and San Cristobal. These results are not consistent with a simple relationship between island area and genetic diversity and instead likely reflect a combination of evolution in isolation following vicariance, rare founder events following over-water dispersal, and possible episodes of secondary contact.

evolutionary biology↗

bioRxiv2025

An ERF transcription factor StPTI5, a novel regulator of endophyte community maintenance in potato

We have recently identified ERF transcription factor PTI5 as a susceptibility factor, negatively regulating immune response to diverse pathogens. Here we investigated the processes involved in colonisation of potato with beneficial organisms. RNAseq showed that at the time of Bacillus subtilis biofilm establishment, immune responses in interacting roots were attenuated, and complex transcriptional network was triggered, with ethylene signalling being a central module and PTI5 strongly induced. Interestingly, the response is intensified if plants are inoculated by two antagonistic B. subtilis strains. While PTI5 is not involved in the establishment of biofilm on roots, we show that bacterial abundance increases in PTI5-silenced plants. Remarkably, root colonization by the arbuscular mycorrhizal fungus Rhizophagus irregularis was also higher in the PTI5-silenced plants. PTI5 is thus involved both in blocking defence against harmful and blocking colonisation with beneficial microbes. Such mechanistic understanding of plant-microbe interaction paves the way for sustainable crop management.

plant biology↗

bioRxiv2024

Primed responses to damage signals mediate mycorrhiza-induced resistance in tomato plants

Arbuscular mycorrhizal fungi establish mutualistic associations with the roots of most vascular plants, enhancing plant immunity and activating mycorrhiza-induced resistance (MIR). In this study, we hypothesised that differential recognition of endogenous damage signals contributes to MIR in tomato plants. To test the hypothesis, we compared responses in mycorrhizal and non-mycorrhizal tomato plants after applying the cell-wall derived damage signal oligogalacturonides (OGs). We analysed the proteomic and metabolomic profiles, and the expression of marker genes related to plant defense, and the effects on plant resistance to the necrotrophic pathogen Botrytis cinerea. Our results show that mycorrhizal plants are more sensitive to these damage signals, as they respond to lower doses and exhibit stronger responses at the protein and metabolic level compared to non-mycorrhizal plants. Mycorrhizal plants showed primed accumulation of defense proteins, receptor kinases, flavonoids, and activation of the jasmonic acid and ethylene signaling pathways in response to OGs. Expression levels of the wall-associated kinase 1 (slWAK1) gene, coding for an OG receptor kinase in tomato, are elevated in mycorrhizal plants, and MIR against B. cinerea is abolished in a wak1 mutant. Together, these results provide the first indication that self-damage recognition is essential to induce MIR against B. cinerea. HighlightMycorrhizal tomato plants exhibit enhanced sensitivity to damage signals, leading to primed defense responses and induced resistance to fungal pathogens.

plant biology↗

bioRxiv2024

Ethylene signaling is essential for mycorrhiza-induced resistance against chewing herbivores in tomato

Root colonization by certain beneficial microbes can prime plant defenses aboveground, modifying plant responses to potential attackers. Arbuscular mycorrhizal (AM) fungi establish mutualistic symbiosis with most plant species, usually enhancing plant resistance to biotic stresses, leading to Mycorrhiza-Induced Resistance (MIR). Still, our knowledge of the complex molecular regulation leading to MIR is very limited. Here we show that the AM fungus Funneliformis mosseae protects tomato plants against two different chewing herbivores, Spodoptera exigua and Manduca sexta, and we explore the underlying molecular mechanism. We explore the impact of AM symbiosis on the plant response to the herbivores through genome-wide transcriptional profiling, followed by bioinformatics network analyses and functional bioassays. Herbivore-triggered JA-regulated defenses were primed in leaves of mycorrhizal plants, while ET biosynthesis and signaling was also higher both before and after herbivory. We hypothesized that fine-tuned ET signaling is required for the primed defensive response leading to MIR in mycorrhizal plants. We followed analytical, functional, and genetic approaches to test this hypothesis and get mechanistic insights into the ET signaling in MIR. ET is a complex regulator of plant responses to stress, and although ET is generally considered a negative regulator of plant defenses against herbivory, tomato lines deficient in ET synthesis or perception could not develop MIR against either herbivore. Thus, we demonstrate that hormone crosstalk is central to the priming of plant immunity by beneficial microbes, with ET fine-tuning being essential for the primed JA biosynthesis and boosted defenses leading to MIR in tomato.

plant biology↗

bioRxiv2018

Psidium guajava in the Galapagos Islands: population genetics and history of an invasive species

The threat of invasive plant species in island populations prompts the need to better understand their population genetics and dynamics. In the Galapagos islands, this is exemplified by the introduced guava (Psidium guajava), considered one of the greatest threats to the local biodiversity due to its effective spread in the archipelago and its ability to outcompete endemic species. To better understand its history and genetics, we analyzed individuals from three inhabited islands in the Galapagos archipelago with 11 SSR markers. Our results reveal similar genetic diversity between islands, suggestive of gene flow between them. Populations appear to be distinct between the islands of San Cristobal and Isabela, with the population of Santa Cruz being composed as a mixture from both. Additional evidence for genetic bottlenecks and the inference of introduction events suggests an original introduction of the species in San Cristobal, from where it was later introduced to Isabela, and finally into Santa Cruz. Alternatively, an independent introduction event for Isabela is also possible. These results are contrasted with the historical record, providing a first overview of the history of P. guajava in the Galapagos islands and its current population dynamics.

evolutionary biology↗

bioRxiv2018

Vesicular delivery of the antifungal antibiotics of Lysobacter enzymogenes C3

Lysobacter enzymogenes C3 is a predatory strain of gram-negative gliding bacteria that produces antifungal antibiotics by the polyketide synthetic pathway. Outer membrane vesicles (OMV) are formed as a stress response and can deliver virulence factors to host cells. The production of OMV by C3 and their role in antifungal activity are reported here. Vesicles in the range of 130-150 nm in diameter were discovered in the cell-free supernatants of C3 cultures. These OMV contain molecules characteristic of bacterial outer membranes, such as lipopolysaccharide and phospholipids. In addition, they contain chitinase activity and essentially all of the heat stable antifungal activity in cell supernatants. We show here that C3 OMV can directly inhibit growth of the yeast Saccharomyces cerevisiae as well as the filamentous fungus Fusarium subglutinans. The activity is dependent on physical contact between OMV and the cells. Furthermore, fluorescent lipid labeling of C3 OMV demonstrated transfer of the membrane-associated probe to yeast cells, suggesting the existence of a mechanism of delivery for membrane-associated molecules. Mass spectrometric analysis of C3 OMV extracts indicates the presence of molecules with molecular weights identical to some of the previously identified antifungal products of C3. These data together suggest that OMV act as an important remote mobile component of predation by Lysobacter.\n\nImportanceThe data presented here suggest a newly discovered function of outer membrane vesicles (OMV) that are produced from the outer membrane of the bacterial species Lysobacter enzymogenes C3. We show that these OMV can be released from the surface of the cells to deliver antibiotics to target fungal organisms as a mechanism of killing or growth inhibition. Understanding the role of OMV in antibiotic delivery can generally lead to improved strategies for dealing with antibiotic-resistant organisms. These results also add to the evidence that some bacterially produced antibiotics can be discovered and purified using methods designed for isolation of nanoscale vesicles. Information on these systems can lead to better identification of active molecules or design of delivery vehicles for these molecules.

microbiology↗