Bacterial Seed Endophytes of the Holoparasitic Cistanche Armena and C. Phelypaea (Orobanchaceae) from Saline Habitats: Semi-Deserts vs Flooded Coasts

The current study compares the bacterial seed endomicrobiomes of the endemic holoparasitic plant species Cistanche armena and C. phelypaea. Both species thrive in habitats that are saline but with a very different soil water status. The study aims to uncover how environmental conditions influence the diversity of the bacterial communities of seeds of these holoparasites and also highlights the physiological activities, several enzymatic and PGP traits of culturable endophytes that may support the tolerance of their hosts to abiotic stresses. A combination of culture-dependent and molecular techniques was employed for the identification of the seed endomicrobiome (culturable and unculturable). From the seeds of both parasitic plant species closely related strains were isolated. Sixteen phyla, 323 genera and 710 bacterial species were identified, mainly Gram negative, halotolerant bacteria with an environmental origin. Most of the isolates were endospore forming, halotolerant and alkaliphile Bacillus spp. which suggests that the endophytic bacteria of C. armena and C. phelypaea seeds possess traits that are correlated with the natural habitat of their hosts. The Paenibacillus strains from both plant species demonstrate similar biochemical traits. Although the seed endophytic microbiomes of C. armena and C. phelypaea contain a high number of common bacterial taxa, also remarkable differences exist. We demonstrated that the diversity of the bacterial communities is related to the environmental conditions, water status or abiotic stresses.

Global patterns and rates of habitat transitions across the eukaryotic tree of life

The successful colonisation of new habitats has played a fundamental role during the evolution of life. Salinity is one of the strongest barriers for organisms to cross, which has resulted in the evolution of distinct marine and terrestrial (including both freshwater and soil) communities. Although microbes represent by far the vast majority of eukaryote diversity, the role of the salt barrier in shaping the diversity across the eukaryotic tree is poorly known. Traditional views suggest rare and ancient marine-terrestrial transitions, but this view is being challenged by the discovery of several recently transitioned lineages. Here, we investigate habitat evolution across the tree of eukaryotes using a unique set of taxon-rich environmental phylogenies inferred from a combination of long-read and short-read metabarcoding data spanning the ribosomal DNA operon. Our results show that overall marine and terrestrial microbial communities are phylogenetically distinct, but transitions have occurred in both directions in almost all major eukaryotic lineages, with at least 350 transition events detected. Some groups have experienced relatively high rates of transitions, most notably fungi for which crossing the salt barrier has most likely been an important aspect of their successful diversification. At the deepest phylogenetic levels, ancestral habitat reconstruction analyses suggest that eukaryotes may have first evolved in non-saline habitats, and that the two largest known eukaryotic assemblages (TSAR and Amorphea) arose in different habitats. Overall, our findings indicate that crossing the salt barrier has played an important role in eukaryotic evolution by providing new ecological niches to fill.

Trade-Off Relationships of Leaf Functional Traits of Lycium ruthenicum in Response to Soil Properties in the Lower Reaches of Heihe River, Northwest China

Soil properties affect plant growth and cause variation in leaf functional traits. Lycium ruthenicum Murray is one of the desert dominant shrubs and halophytes in the lower reaches of Heihe River, Northwest China. We analyzed the trade-off relationships of 14 leaf functional traits of eight L. ruthenicum populations growing at varying distances from the river and discussed the effects that soil properties have on leaf functional traits. The results showed that: Lower leaf nitrogen (N) content indicated that L. ruthenicum was located at the slow investment–return axis of the species resource utilization graph. Compared with non-saline and very slightly saline habitats, populations of slightly saline habitats showed a higher carbon to nitrogen ratio (C:N). Redundancy analysis (RDA) revealed a relatively strong relationship between leaf functional traits and soil properties, the first RDA axis accounted for 70.99 and 71.09% of the variation in 0–40 and 40–80 cm of soil properties. Relative importance analysis found that in the 0–40 cm soil layer, leaf traits variations were mainly influenced by soil moisture (SWC), HCO3− and CO32− ions content, while leaf traits variations in the 40–80 cm soil layer were mainly influenced by HCO3− and SO42−. L. ruthenicum has a foliar resource acquisition method and a resource conservation trade-off with a flexible life history strategy in habitats with drought and salinity stress. In the shallow soil layers, water affects leaf traits variation greater than salt , and in both shallow and deep soil layers, HCO3− plays a dominant role on leaf traits. This study provides insights into the adversity adaptation strategies of desert plants and the conservation and restoration of arid-saline ecosystems.

Intraspecific variation in elemental accumulation and its association with salt tolerance in Paspalum vaginatum

Most plant species, including most crops, perform poorly in salt-affected soils because high sodium levels are cytotoxic and can disrupt uptake of water and important nutrients. Halophytes are species that have evolved adaptations to overcome these challenges and may be a useful source of knowledge for salt tolerance mechanisms and genes that may be transferable to crop species. The salt content of saline habitats can vary dramatically by location, providing ample opportunity for different populations of halophytic species to adapt to their local salt concentrations; however, the extent of this variation, and the physiology and polymorphisms that drive it, remain poorly understood. Differential accumulation of inorganic elements between genotypes or populations may play an important role in local salinity adaptation. To test this, we investigated the relationships between population structure, tissue ion concentrations and salt tolerance in 17 “fine-textured” genotypes of the halophytic turfgrass seashore paspalum (Paspalum vaginatum Swartz). A high-throughput ionomics pipeline was used to quantify the shoot concentration of 18 inorganic elements across three salinity treatments. We found a significant relationship between population structure and ion accumulation, with strong correlations between principal components derived from genetic and ionomic data. Additionally, genotypes with higher salt tolerance accumulated more K and Fe and less Ca than less tolerant genotypes. Together these results indicate that differences in ion accumulation between P. vaginatum populations may reflect locally adapted salt stress responses.

Establishment of a Simplified System to Evaluate Salinity Preference and Validation of Behavioral Salinity Selection in the Japanese Medaka, Oryzias latipes

In fishes, it is necessary to select a salinity environment suitable for survival. However, little is known about the mechanisms regarding detection and selection of salinity environments in fish. This study involved the establishment of a simple aquarium system in which fish can swim between freshwater (FW) and seawater (SW) in a single tank. In this tank, the lower level contained SW, the upper level contained FW, and the FW and SW levels were clearly separated as different salinity areas. Behavioral experiments of salinity environment selection using this simplified system to evaluate salinity preference showed that FW-acclimated medakas preferred FW to SW. In contrast, SW-acclimated medakas preferred SW to FW. These results indicate that euryhaline medakas prefer the saline habitats to which they are acclimated, when able to select the salinity environment. We identified the taste receptor type-2 and polycystic kidney disease 2-like 1 genes as possibly related to high-salinity taste in medaka. The expression of these genes increased at certain time points after SW challenges. In this study, we established an aquarium system to facilitate a simple experiment for salinity preference. Our results suggest that the medaka is good model for research related to seawater environment selection in fish.

Trade-off relationship of leaf functional traits of desert halophyte Lycium ruthenicum in the lower reaches of Heihe River, Northwest China: response to soil moisture and salinity

Background: Soil salinization affects plant growth and causes changes in leaf traits. Lycium ruthenicum Murr. is one of the dominant shrubs and halophytes in the lower reaches of the Heihe River in Northwest China. We analyzed the trade-off relationship of fourteen leaf functional traits of eight L.ruthenicum populations growing at varying distances from the Heihe River, and discussed the effects that soil moisture and salinity have on leaf functional traits. Results: Lower nitrogen (N) contents indicated that L.ruthenicum was located at the slow investment-return axis of the species resource utilization graph. Compared with non-saline and very slightly saline sites, populations of slightly saline sites showed higher carbon to nitrogen ratio (C:N). Redundancy analysis (RDA) revealed a relatively strong relationship between leaf functional traits and soil properties, the first RDA axis accounted for 70.99 % and 71.09 % of the variation in 0-40 cm and 40-80 cm of soil moisture and salinity. Populations in non-saline and very slightly saline habitats tended to have higher leaf C content, whereas populations in slightly saline habitats tended to have lower leaf C content, and the discrepancy was evident. Relative importance analysis found that in the 0-40 cm soil layer, leaf traits variations were mainly influenced by soil moisture (SWC), HCO3- and CO32- ions content, while leaf trait variations in the 40-80 cm soil layer were mainly influenced by HCO3- and SO42-. Conclusions: The leaf functional traits of L. ruthenicum in this region are mainly restricted by soil N content. The L.ruthenicum populations formed a pattern of increased C:N ratios and C content, reduced nitrogen to phosphorus ratio (N:P) and N content from very slightly saline soil to slightly saline. L.ruthenicum has a foliar resource acquisition method and a resource conservation trade-off with a flexible life history strategy in habitats with drought and salinity stress. In the shallow soil layers, water affects greater than salt on leaf traits variation; in both shallow and deep soil layers, HCO3- plays a dominant role on leaf traits. We believe that these findings will provide some baseline information to facilitate the management and restoration of arid-saline desert ecosystems.

DISTRIBUTION OF INVASIVE SPECIES PROSOPIS JULIFLORA (MIMOSACEAE) IN FUJAIRA (UAE)

The article analyzes the secondary area in the Emirate of Fujairah, as well as the peculiarities of seed dispersing, seed germination and early seedling development of Mesquite, or Prosopis juliflora - the alien species of Mimosaceae, which appeared on the territory of the Emirates in the twentieth century, and one of the first collected herbarium specimen is dated 1983. In the secondary area most often, the Mesquite is found in anthropogenic habitats: in gardens, as well as near roads, on waste grounds, less frequent on the streets of settlements, garden fences etc. In regions represented by herbarium collections, P. juliflora is successfully naturalized and creates stable self-sustaining populations. It has a complex of specific helio-mesomorphic features that allow it to take root successfully in relatively open moderately wet, and even dry or saline habitats and compete with native species of acacia ( Acacia tortilis, A. ehrenbergii ) and local prosopis ( P. cineraria ). Characteristics such as good germination, significant morphological, dimensional and temporal variability of premature individuals of P. juliflora , identified in this work, undoubtedly contribute to the successful naturalization of the species in the secondary range and its wide distribution throughout the Emirate. Due to the high aggressiveness of Mesquite, it is necessary to develop a method of dealing with this plant in the UAE, which will stop its uncontrolled settlement in the region. We have compiled a map of Mesquite distribution in Fujairah and surrounding areas, which clearly shows the scale of the disaster. A method for assessing invasion on a five-level scale based on reproductive success has been developed and applied. The structure of ecotopes at an early and middle stage of penetration of P. juliflora was analyzed using large wastelands (2 and 1.2 ha) in the village Mirbah and the city of Fujairah on the coast of the Gulf of Oman.

Intraspecific variation in elemental accumulation and its association with salt tolerance in Paspalum vaginatum

Most plant species, including most crops, perform poorly in salt-affected soils because high sodium levels are cytotoxic and can disrupt uptake of water and important nutrients. Halophytes are species that have evolved adaptations to overcome these challenges and may be a useful source of knowledge for salt tolerance mechanisms and genes that may be transferable to crop species. The salt content of saline habitats can vary dramatically by location, providing ample opportunity for different populations of halophytic species to adapt to their local salt concentrations; however, the extent of this variation, and the physiology and polymorphisms that drive it, remain poorly understood. Differential accumulation of inorganic elements between genotypes or populations may play an important role in local salinity adaptation. To test this, we investigated the relationships between population structure, tissue ion concentrations (i.e., ionomic profiles) and salt tolerance in 17 fine-textured genotypes of the halophytic turfgrass seashore paspalum (Paspalum vaginatum Swartz). A high-throughput ionomics pipeline was used to quantify the shoot concentration of 18 inorganic elements across three salinity treatments. We found a significant relationship between population structure and ion accumulation, with strong correlations between principal components derived from genetic and ionomic data. Additionally, genotypes with higher salt tolerance accumulated more K and Fe and less Ca than less tolerant genotypes. Together these results indicate that differences in ion accumulation between P. vaginatum populations may reflect locally adapted salt stress responses.

Recent Advances in a Polydopamine-Mediated Antimicrobial Adhesion System

The drug resistance developed by bacteria during antibiotic treatment has been a call to action for researchers and scientists across the globe, as bacteria and fungi develop ever increasing resistance to current drugs. Innovative antimicrobial/antibacterial materials and coatings to combat such infections have become a priority, as many infections are caused by indwelling implants (e.g., catheters) as well as improving postsurgical function and outcomes. Pathogenic microorganisms that can exist either in planktonic form or as biofilms in water-carrying pipelines are one of the sources responsible for causing water-borne infections. To combat this, researchers have developed nanotextured surfaces with bactericidal properties mirroring the topographical features of some natural antibacterial materials. Protein-based adhesives, secreted by marine mussels, contain a catecholic amino acid, 3,4-dihydroxyphenylalanine (DOPA), which, in the presence of lysine amino acid, empowers with the ability to anchor them to various surfaces in both wet and saline habitats. Inspired by these features, a novel coating material derived from a catechol derivative, dopamine, known as polydopamine (PDA), has been designed and developed with the ability to adhere to almost all kinds of substrates. Looking at the immense potential of PDA, this review article offers an overview of the recent growth in the field of PDA and its derivatives, especially focusing the promising applications as antibacterial nanocoatings and discussing various antimicrobial mechanisms including reactive oxygen species-mediated antimicrobial properties.