Secondary Metabolites Produced by Trees and Fungi: Achievements So Far and Challenges Remaining

Abstract

Secondary metabolites are ubiquitous substances occurring naturally in trees and microorganisms. They are produced in various metabolic pathways which determine their structure and biochemical proprieties. However, the biological functions of many secondary metabolites remain undetermined. Usually, the amounts of secondary metabolites produced by trees under natural conditions are limited, which makes their mass production difficult and not cost-effective. Metabolites occurring naturally in plants, including gymnosperm and angiosperm trees, as well as in fungi, are important biologically active substances used by many industries and in modern medicine. The huge variability and potential of biological activity present in secondary metabolites make it possible to replace most of them with compounds of completely natural origin. The current breakdown of metabolites, together with the most important examples of compounds and their uses, are presented in this overview. The possibility of increasing the number of secondary metabolites in a specific environment through interaction with the most known biotic factors is discussed. The use of in vitro culture for the production of secondary metabolites and their extraction, as well as the possibility of subsequent analysis, are described. The current literature on the metabolites produced by individual species is presented.

Epigenetics as a Regulator of Tree Specialized Metabolites In Vitro Production

“…Specialized metabolites represent over two million natural molecules depending on plant taxa. In opposition to primary metabolites (proteins, lipids, sugars, and nucleic acids) accumulating in substantial amounts and essential for growth and development, secondary metabolites correspond to low-level and tissue-specific molecules playing key roles in ecological interactions with biotic or abiotic factors and in general adaptation to environmental variations [1,2]. Four major groups have been identified in plants: terpenoids, phenolic compounds, alkaloids, and sulfur-containing compounds.…”

“…The most famous example is the production of paclitaxel by the Taxus tree species [3]. Recently, the current state of knowledge about specialized metabolites in forest trees as well as the opportunities and methods to improve their production was reported [1]. Forest trees are long-living plants, with high natural diversity in terms of species, populations, and individuals.…”

“…Forest trees are long-living plants, with high natural diversity in terms of species, populations, and individuals. Forest ecosystems are constantly subjected to microclimate changes and biotic interactions, giving rise to a complex diversity of natural compounds that are underestimated for human resources [1]. While omics studies, mostly transcriptomic and metabolomic, have allowed the identification of many metabolite pathways [4,5], in vitro production is still facing difficulties in producing high-yield and low-cost specialized metabolites.…”

“…Potential applications of epigenetics for crop improvement and particularly using in vitro systems have been extensively reviewed [8][9][10][11]. The focus here is on forest trees, which represent an important and scarcely exploited source of natural specialized metabolites with a wide range of applications for human [1] (Figure 1). The generation of epi/genetically modified cell lines using various technical approaches (genetic, pharmacologic, and based on genomic edition) specifically blocking the DRM pathway or affecting phytohormonal or redox signaling pathways could provide resistance to silencing and ensure stable or even increased (cryptic) highly productive bioreactor cultures (Figure 1).…”

Medicago sativa Extracts Enhance the Anticancer Efficacy of GEM in PANC-1 Cells through Apoptosis Induction and BAX/BCL-2/CASP3 Expression Modulation

“…Secondary metabolites are common compounds that naturally arise in microbes and plants, and their structure and biological properties are determined by the metabolic routes through which they are created [15,16]. Secondary structural metabolites include alkaloids, terpenoids, organosulfur compounds, and polyphenols [17].…”