Copper treatment during storage reduces Phytophthora and Halophytophthora infection of Zostera marina seeds used for restoration

Exploring Fungal Diversity in Seagrass Ecosystems for Pharmaceutical and Ecological Insights

Marine ecosystems are important in discovering novel fungi with interesting metabolites that have shown great potential in pharmaceutical and biotechnological industries. Seagrasses, the sole submerged marine angiosperm, host diverse fungal taxa with mostly unknown metabolic capabilities. They are considered to be one of the least studied marine fungal habitats in the world. This review gathers and analyzes data from studies related to seagrasses-associated fungi, including taxonomy and biogeography, and highlights existing research gaps. The significance of the seagrass-fungal associations remains largely unknown, and current understanding of fungal diversity is limited to specific geographical regions such as the Tropical Atlantic, Mediterranean, and Indo-Pacific. Our survey yielded 29 culture-dependent studies on seagrass-associated endophytic and epiphytic fungi, and 13 miscellaneous studies, as well as 11 meta-studies, with no pathogenic true fungi described. There is a significant opportunity to expand existing studies and conduct multidisciplinary research into novel species and their potential applications, especially from understudied geographical locations. Future research should prioritize high-throughput sequencing and mycobiome studies, utilizing both culture-dependent and -independent approaches to effectively identify novel seagrass-associated fungal taxa.

Unravelling the Lipids Content and the Fatty Acid Profiles of Eight Recently Described Halophytophthora Species and H. avicennae from the South Coast of Portugal

In this study, mycelia of eight recently described species of Halophytophthora and H. avicennae collected in Southern Portugal were analysed for lipids and fatty acids (FA) content to evaluate their possible use as alternative sources of FAs and understand how each species FAs profile relates to their phylogenetic position. All species had a low lipid percentage (0.06% in H. avicennae to 0.28% in H. frigida). Subclade 6b species contained more lipids. All species produced monounsaturated (MUFA), polyunsaturated (PUFA) and saturated (SFA) FAs, the latter being most abundant in all species. H. avicennae had the highest FA variety and was the only producer of γ-linolenic acid, while H. brevisporangia produced the lowest number of FAs. The best producer of arachidonic acid (ARA) and eicosapentaenoic acid (EPA) was H. thermoambigua with 3.89% and 9.09% of total FAs, respectively. In all species, palmitic acid (SFA) was most abundant and among the MUFAs produced oleic acid had the highest relative percentage. Principal component analysis (PCA) showed partial segregation of species by phylogenetic clade and subclade based on their FA profile. H. avicennae (Clade 4) differed from all other Clade 6 species due to the production of γ-linolenic and lauric acids. Our results disclosed interesting FA profiles in the tested species, adequate for energy (biodiesel), pharmaceutical and food industries (bioactive FAs). Despite the low amounts of lipids produced, this can be boosted by manipulating culture growth conditions. The observed interspecific variations in FA production provide preliminary insights into an evolutionary background of its production.

Specialized compounds across ontogeny in the seagrass Posidonia oceanica

Differences in phenolic composition across different ontogenic stages can be crucial in determining the interaction outcomes between plants and their surrounding biotic environment. In seagrasses, specific phenolic compounds have rarely been analyzed and remain unexplored in ontogenic stages other than non-reproductive adults. Furthermore, it is generally accepted that plants would prioritize defense (e.g., through increased phenolic content) on tissues or stages that are critical for plant fitness but how this affects nutritional quality or plant resources has been scarcely explored. We analyzed how phenolic composition, N and C content and carbohydrate resources varied among different life stages (i.e. old and young leaves of reproductive and non-reproductive plants, and leaves of seedlings) in the seagrass Posidonia oceanica. We identified five phenolic compounds, whose structures were established as hydroxycinnamate esters of tartaric acid. Also, our results show that in all examined ontogenic stages phenolic compounds have the same qualitative composition but inflorescences exhibit higher contents than vegetative tissues. We did not find a reduction in stored resources in reproductive plants, pointing to some kind of compensatory mechanism in the production or storage of resources. In contrast, seedlings seemed to have less phenolic compounds than reproductive plants, perhaps due to limited resources available to allocate to phenolic production. Our results demonstrate how different ontogenic stages change their investment in specialized phenolic compounds prioritizing different functions according to the needs and limitations of that stage.

Programmed responses of different life-stages of the seagrass Ruppia sinensis to copper and cadmium exposure

Seagrass meadows are recognized as crucial and are among the most vulnerable habitats worldwide. The aquatic plant genus Ruppia is tolerant of a wide salinity range, and high concentrations of trace metals. However, the tolerance of its early life stages to such trace metal exposure is unclear. Thus, the current study investigated the trace metal-absorbing capacity of three different life-history stages of Ruppia sinensis, a species that is widely distributed in China, by observing toxic symptoms at the individual, subcellular, and transcription levels. The seedling period was the most vulnerable, with visible toxic effects at the individual level in response to 50 μM copper and 500 μM cadmium after 4 days of exposure. The highest concentrations of trace metals occurred in the vacuoles and cytoplasmic structures of aboveground tissues. Genes related to signal identification and protein processing were significantly downregulated after 4 days of exposure to copper and cadmium. These results provide information relating to the strategies evolved by R. sinensis to absorb and isolate trace elements, and highlight the phytoremediation potential of this species.

Salinity, pH and temperature growth ranges of Halophytophthora isolates suggest their physiological adaptations to mangrove environments

Species of Halophytophthora are early colonisers of fallen mangrove leaves in the tropics but recently found commonly in temperate areas. In mangrove habitats, temperature and salinity change rapidly daily (high/low tide) and seasonally (summer/winter, rainy/dry seasons). Mangrove organisms have to develop adaptive strategies to thrive in such a physiologically challenging environment. In this study, growth of three isolates of Halophytophthora avicenniae and two isolates of H. batemanensis was tested under combined effects of 3 temperatures (15°C, 25°C, 37°C), 3 pHs (6, 7, 8) and 4 salinities (4 ‰, 8 ‰, 16 ‰, 32 ‰). No/little growth was observed at 37°C and growth saturation occurred earlier at 25°C than at 15°C. The log phase of growth was steeper at pH 6 than pH 7 and 8. Temperature and pH were found to exert a greater effect on growth than salinity. Generally, a reduction of growth rate was observed at pH 8 and 15°C. Increase in salinity caused a slight decrease in growth, most noticeable at 32 ‰. The wide growth ranges of temperature, salinity and pH of Halophytophthora isolates suggest that they are well adapted to the physical and chemical conditions of mangrove habitats.

Seed selection and storage with nano-silver and copper as potential antibacterial agents for the seagrass Zostera marina: implications for habitat restoration

Globally, seagrass meadows are extremely important marine ecosystems that are disappearing at an alarming rate. Therefore, research into seagrass restoration has become increasingly important. Various strategies have been used in Zostera marina L. (eelgrass) restoration, including planting seeds. To improve the efficiency of restoration by planting seeds, it is necessary to select high-quality seeds. In addition, a suitable antibacterial agent is necessary for wet storage of desiccation sensitive seeds to reduce or inhibit microorganism infection and seed decay. In the present study, an efficient method for selecting for high-quality eelgrass seeds using different specific gravities of salt water was developed, and potential antibacterial agents (nano-silver and copper sulfate) for seed storage were assessed. The results showed that the highest proportion of intact seeds (72.91 ± 0.50%) was recorded at specific gravities greater than 1.20. Therefore, specific gravities greater than 1.20 can be used for selecting high-quality eelgrass seeds. During seed storage at 0 °C, the proportion of intact seeds after storage with nano-silver agent was over 90%, and also higher than 80% with copper sulfate agent, which was significantly higher than control treatments. The findings revealed a potential selection method for high-quality seeds and long-term seed storage conditions for Z. marina, which could facilitate conservation and habitat restoration.

Review: Host-pathogen dynamics of seagrass diseases under future global change

Human-induced global change is expected to amplify the disease risk for marine biota. However, the role of disease in the rapid global decline of seagrass is largely unknown. Global change may enhance seagrass susceptibility to disease through enhanced physiological stress, while simultaneously promoting pathogen development. This review outlines the characteristics of disease-forming organisms and potential impacts of global change on three groups of known seagrass pathogens: labyrinthulids, oomycetes and Phytomyxea. We propose that hypersalinity, climate warming and eutrophication pose the greatest risk for increasing frequency of disease outbreaks in seagrasses by increasing seagrass stress and lowering seagrass resilience. In some instances, global change may also promote pathogen development. However, there is currently a paucity of information on these seagrass pathosystems. We emphasise the need to expand current research to better understand the seagrass-pathogen relationships, serving to inform predicative modelling and management of seagrass disease under future global change scenarios.