Isotopic composition of aquatic and semiaquatic plants from the Mexican Caribbean: a baseline for regional ecological studies

Primary producers in the aquatic community structure are fundamental elements because they are the first link in the trophic network as occur in most ecosystems. They produce oxygen and biomass, act as a shelter for several species, and provide food for a wide variety of megaherbivore species like manatees and sea turtles. Physicochemical processes taken place in primary producers can be determined through stable isotope analysis (SIA) as natural tracers from elements like carbon and nitrogen, applied in ecological, and physiological studies. In the Mexican Caribbean ecosystems, SIA has been little applied in aquatic plants, where Thalassia testudinum is the main seagrass species studied. Here, we present the isotopic composition (δC and δN) from 95 aquatic and semiaquatic plant species of four vegetation types, from three different environments, hydroclimatic seasons, and geographical zones in the Mexican Caribbean. Main statistical differences in δC and δN were found according to vegetation type and environment. Besides, for δC were also found statistical differences among seasons, while for δN differences were found among zones (H-Test, p < 0.05). This study provides an isotopic baseline for further ecological studies in the region. This information can contribute to understanding the structure of aquatic food webs and infer the diet and feedings habits of aquatic species, as well as to detect possible changes related to anthropogenic activities that can affect the survival of these plant species, and the fauna depending on them.This research was part of N. Garcés-Cuartas Ph.D. thesis from the Sustainable Development Program from the University of Quintana Roo , Mexico, who benefited from CONACYT (Consejo Nacional de Ciencia y Tecnología) graduate fellowship. Logistics at the sampling surveys were partially funded by PADI Foundation (Program: Mammals, Turtles and Birds. App # 28521 ). Laboratory analysis was covered by PRODEP (Mexico), and the Stable Isotopes Biogeochemistry Laboratory from the Instituto Andaluz de Ciencias de la Tierra in Granada (Spain). We especially thank Arsenio Granados Torres for the stable isotope analysis of plant samples. We want to thank the advisors P. Blanco-Parra and P. Barradas-Miranda for their comments to previous versions of this work. Also, we thank Dr. Beth Brady for the document review, as well as two anonymous reviewers for the very helpful suggestions that improved this manuscript. The funders had no role in study design, data analysis, decision to publish or preparation of the manuscript. This research was part of the Monitoring Program of Aquatic Megafauna from the Mexican Caribbean (PROMMAC) (permit: SGPA/DGVS/006294/18 )

Unravelling Darwin's entangled bank: architecture and robustness of mutualistic networks with multiple interaction types

Trying to unravel Darwin's entangled bank further, we describe the architecture of a network involving multiple forms of mutualism (pollination by animals, seed dispersal by birds and plant protection by ants) and evaluate whether this multi-network shows evidence of a structure that promotes robustness. We found that species differed strongly in their contributions to the organization of the multi-interaction network, and that only a few species contributed to the structuring of these patterns. Moreover, we observed that the multi-interaction networks did not enhance community robustness compared with each of the three independent mutualistic networks when analysed across a range of simulated scenarios of species extinction. By simulating the removal of highly interacting species, we observed that, overall, these species enhance network nestedness and robustness, but decrease modularity. We discuss how the organization of interlinked mutualistic networks may be essential for the maintenance of ecological communities, and therefore the long-term ecological and evolutionary dynamics of interactive, species-rich communities. We suggest that conserving these keystone mutualists and their interactions is crucial to the persistence of species-rich mutualistic assemblages, mainly because they support other species and shape the network organization.Field data on ants were supported by a CONACYT grant (no. 903579). P.R.G. and J.N.T. were supported by FAPESP and NSF, respectively. L.P.M. was supported by FAPESP (2015/12956-7)

Unravelling Darwin's entangled bank: architecture and robustness of mutualistic networks with multiple interaction types

Trying to unravel Darwin's entangled bank further, we describe the architecture of a network involving multiple forms of mutualism (pollination by animals, seed dispersal by birds and plant protection by ants) and evaluate whether this multi-network shows evidence of a structure that promotes robustness. We found that species differed strongly in their contributions to the organization of the multi-interaction network, and that only a few species contributed to the structuring of these patterns. Moreover, we observed that the multi-interaction networks did not enhance community robustness compared with each of the three independent mutualistic networks when analysed across a range of simulated scenarios of species extinction. By simulating the removal of highly interacting species, we observed that, overall, these species enhance network nestedness and robustness, but decrease modularity. We discuss how the organization of interlinked mutualistic networks may be essential for the maintenance of ecological communities, and therefore the long-term ecological and evolutionary dynamics of interactive, species-rich communities. We suggest that conserving these keystone mutualists and their interactions is crucial to the persistence of species-rich mutualistic assemblages, mainly because they support other species and shape the network organization

eIF4A/PDCD4 Pathway, a Factor for Doxorubicin Chemoresistance in a Triple-Negative Breast Cancer Cell Model

Cells employ several adaptive mechanisms under conditions of accelerated cell division, such as the unfolded protein response (UPR). The UPR is composed of a tripartite signaling system that involves ATF6, PERK, and IRE1, which maintain protein homeostasis (proteostasis). However, deregulation of protein translation initiation could be associated with breast cancer (BC) chemoresistance. Specifically, eukaryotic initiation factor-4A (eIF4A) is involved in the unfolding of the secondary structures of several mRNAs at the 5′ untranslated region (5′-UTR), as well as in the regulation of targets involved in chemoresistance. Importantly, the tumor suppressor gene PDCD4 could modulate this process. This regulation might be disrupted in chemoresistant triple negative-BC (TNBC) cells. Therefore, we characterized the effect of doxorubicin (Dox), a commonly used anthracycline medication, on human breast carcinoma MDA-MB-231 cells. Here, we generated and characterized models of Dox chemoresistance, and chemoresistant cells exhibited lower Dox internalization levels followed by alteration of the IRE1 and PERK arms of the UPR and triggering of the antioxidant Nrf2 axis. Critically, chemoresistant cells exhibited PDCD4 downregulation, which coincided with a reduction in eIF4A interaction, suggesting a sophisticated regulation of protein translation. Likewise, Dox-induced chemoresistance was associated with alterations in cellular migration and invasion, which are key cancer hallmarks, coupled with changes in focal adhesion kinase (FAK) activation and secretion of matrix metalloproteinase-9 (MMP-9). Moreover, eIF4A knockdown via siRNA and its overexpression in chemoresistant cells suggested that eIF4A regulates FAK. Pro-atherogenic low-density lipoproteins (LDL) promoted cellular invasion in parental and chemoresistant cells in an MMP-9-dependent manner. Moreover, Dox only inhibited parental cell invasion. Significantly, chemoresistance was modulated by cryptotanshinone (Cry), a natural terpene purified from the roots of Salvia brandegeei. Cry and Dox co-exposure induced chemosensitization, connected with the Cry effect on eIF4A interaction. We further demonstrated the Cry binding capability on eIF4A and in silico assays suggest Cry inhibition on the RNA-processing domain. Therefore, strategic disruption of protein translation initiation is a druggable pathway by natural compounds during chemoresistance in TNBC. However, plasmatic LDL levels should be closely monitored throughout treatment

Supplementary material from “Unraveling Darwin's entangled bank: architecture and robustness of mutualistic networks with multiple interaction types”

Multi-interaction network involving different types of mutualism (animal pollination, seed-dispersal by frugivorous birds, and anti-herbivore defense by protective ants) sampled in a coastal tropical environment in Mexico

Abundance drives broad patterns of generalisation in hummingbird-plant pollination networks

Abundant pollinators are often more generalised than rare pollinators. This could be because abundant species have more chance encounters with potential interaction partners. On the other hand, generalised species could have a competitive advantage over specialists, leading to higher abundance. Determining the direction of the abundance-generalisation relationship is therefore a ‘chicken-and-egg’ dilemma. Here we determine the direction of the relationship between abundance and generalisation in plant-hummingbird pollination networks across the Americas. We find evidence that hummingbird pollinators are generalised because they are abundant, and little evidence that hummingbirds are abundant because they are generalised. Additionally, most patterns of species-level abundance and generalisation were well explained by a null model that assumed interaction neutrality (interaction probabilities defined by species relative abundances). These results suggest that neutral processes play a key role in driving broad patterns of generalisation in animal pollinators across large spatial scales