New types of ATP-grasp ligase are associated with the novel pathway for complicated mycosporine-like amino acid production in desiccation-tolerant cyanobacteria

Molecular insights and omics-based understanding of plant-microbe interactions under drought stress

The detrimental effects of adverse environmental conditions are always challenging and remain a major concern for plant development and production worldwide. Plants deal with such constraints by physiological, biochemical, and morphological adaptations as well as acquiring mutual support of beneficial microorganisms. As many stress-responsive traits of plants are influenced by microbial activities, plants have developed a sophisticated interaction with microbes to cope with adverse environmental conditions. The production of numerous bioactive metabolites by rhizospheric, endo-, or epiphytic microorganisms can directly or indirectly alter the root system architecture, foliage production, and defense responses. Although plant-microbe interactions have been shown to improve nutrient uptake and stress resilience in plants, the underlying mechanisms are not fully understood. "Multi-omics" application supported by genomics, transcriptomics, and metabolomics has been quite useful to investigate and understand the biochemical, physiological, and molecular aspects of plant-microbe interactions under drought stress conditions. The present review explores various microbe-mediated mechanisms for drought stress resilience in plants. In addition, plant adaptation to drought stress is discussed, and insights into the latest molecular techniques and approaches available to improve drought-stress resilience are provided.

A Plastic Biosynthetic Pathway for the Production of Structurally Distinct Microbial Sunscreens

Mycosporine-like amino acids (MAAs) are small, colorless, and water-soluble secondary metabolites. They have high molar extinction coefficients and a unique UV radiation absorption mechanism that make them effective sunscreens. Here we report the discovery of two structurally distinct MAAs from the lichen symbiont strain Nostoc sp. UHCC 0926. We identified these MAAs as aplysiapalythine E (C23H38N2O15) and tricore B (C34H53N4O15) using a combination of high-resolution liquid chromatography-mass spectrometry (HR-LCMS) analysis and nuclear magnetic resonance (NMR) spectroscopy. We obtained a 8.3 Mb complete genome sequence of Nostoc sp. UHCC 0926 to gain insights into the genetic basis for the biosynthesis of these two structural distinct MAAs. We identified MAA biosynthetic genes encoded in three separate locations of the genome. The organization of biosynthetic enzymes in Nostoc sp. UHCC 0926 necessitates a branched biosynthetic pathway to produce two structurally distinct MAAs. We detected the presence of such discontiguous MAA biosynthetic gene clusters in 12% of the publicly available complete cyanobacterial genomes. Bioinformatic analysis of public MAA biosynthetic gene clusters suggests that they are subject to rapid evolutionary processes resulting in highly plastic biosynthetic pathways that are responsible for the chemical diversity in this family of microbial sunscreens.

Recent progress in unraveling the biosynthesis of natural sunscreens mycosporine-like amino acids

Exposure to ultraviolet (UV) rays is a known risk factor for skin cancer, which can be notably mitigated through the application of sun care products. However, escalating concerns regarding the adverse health and environmental impacts of synthetic anti-UV chemicals underscore a pressing need for the development of biodegradable and eco-friendly sunscreen ingredients. Mycosporine-like amino acids (MAAs) represent a family of water-soluble anti-UV natural products synthesized by various organisms. These compounds can provide a two-pronged strategy for sun protection as they not only exhibit a superior UV absorption profile but also possess the potential to alleviate UV-induced oxidative stresses. Nevertheless, the widespread incorporation of MAAs in sun protection products is hindered by supply constraints. Delving into the biosynthetic pathways of MAAs can offer innovative strategies to overcome this limitation. Here, we review recent progress in MAA biosynthesis, with an emphasis on key biosynthetic enzymes, including the dehydroquinate synthase homolog MysA, the adenosine triphosphate (ATP)-grasp ligases MysC and MysD, and the nonribosomal peptide synthetase (NRPS)-like enzyme MysE. Additionally, we discuss recently discovered MAA tailoring enzymes. The enhanced understanding of the MAA biosynthesis paves the way for not only facilitating the supply of MAA analogs but also for exploring the evolution of this unique family of natural sunscreens.

ONE-SENTENCE SUMMARY

This review discusses the role of mycosporine-like amino acids (MAAs) as potent natural sunscreens and delves into recent progress in their biosynthesis.

Metabolites Facilitating Adaptation of Desert Cyanobacteria to Extremely Arid Environments

Desert is one of the harshest environments on the planet, characterized by exposure to daily fluctuations of extreme conditions (such as high temperature, low nitrogen, low water, high salt, etc.). However, some cyanobacteria are able to live and flourish in such conditions, form communities, and facilitate survival of other organisms. Therefore, to ensure survival, desert cyanobacteria must develop sophisticated and comprehensive adaptation strategies to enhance their tolerance to multiple simultaneous stresses. In this review, we discuss the metabolic pathways used by desert cyanobacteria to adapt to extreme arid conditions. In particular, we focus on the extracellular polysaccharides and compatible solutes biosynthesis pathways and their evolution and special features. We also discuss the role of desert cyanobacteria in the improvement of soil properties and their ecological and environmental impact on soil communities. Finally, we summarize recent achievements in the application of desert cyanobacteria to prevent soil erosion and desertification.

The Preparation of Anti-Ultraviolet Composite Films Based on Fish Gelatin and Sodium Alginate Incorporated with Mycosporine-like Amino Acids

Mycosporine-like amino acids (MAAs) are ultraviolet-absorbing compounds and have antioxidant functions. In this paper, MAAs were added into fish gelatin/sodium alginate films as an anti-ultraviolet additive. The effects of 0–5% MAAs (w/w, MAAs/fish gelatin) on the physical properties, antioxidant properties, antibacterial properties and anti-ultraviolet properties of fish gelatin/sodium alginate films were investigated. The results suggest that the content of the MAAs influenced the mechanical properties. The water content, swelling and water vapor permeability of the films were not altered with the addition of MAAs. In addition, the composite films showed effective antioxidant activity and antimicrobial activity. The incorporation of MAAs significantly improved the DPPH radical scavenging activity of the films from 35.77% to 46.61%. Moreover, the block ultraviolet rays’ ability was also greatly improved when the film mixed with the MAAs and when the value of the light transmission was 0.6% at 350 nm. Compared with the pure composite film, the growth of E. coli covered by the composite film with 3.75% and 5% MAAs exhibited the best survival rate. These results reveal that MAAs are a good film-forming substrate, and MAAs have good potential to prepare anti-ultraviolet active films and antioxidant active films for applications. Overall, this project provides a theoretical basis for the study of active composite films with anti-ultraviolet activities, and it provides new ideas for the application of MAAs.