Production of Plant Secondary Metabolites: Examples, Tips and Suggestions for Biotechnologists

Plants are sessile organisms and, in order to defend themselves against exogenous (a)biotic constraints, they synthesize an array of secondary metabolites which have important physiological and ecological effects. Plant secondary metabolites can be classified into four major classes: terpenoids, phenolic compounds, alkaloids and sulphur-containing compounds. These phytochemicals can be antimicrobial, act as attractants/repellents, or as deterrents against herbivores. The synthesis of such a rich variety of phytochemicals is also observed in undifferentiated plant cells under laboratory conditions and can be further induced with elicitors or by feeding precursors. In this review, we discuss the recent literature on the production of representatives of three plant secondary metabolite classes: artemisinin (a sesquiterpene), lignans (phenolic compounds) and caffeine (an alkaloid). Their respective production in well-known plants, i.e., Artemisia, Coffea arabica L., as well as neglected species, like the fibre-producing plant Urtica dioica L., will be surveyed. The production of artemisinin and caffeine in heterologous hosts will also be discussed. Additionally, metabolic engineering strategies to increase the bioactivity and stability of plant secondary metabolites will be surveyed, by focusing on glycosyltransferases (GTs). We end our review by proposing strategies to enhance the production of plant secondary metabolites in cell cultures by inducing cell wall modifications with chemicals/drugs, or with altered concentrations of the micronutrient boron and the quasi-essential element silicon

Plant cell culture technology in the cosmetics and food industries : current state and future trends

The production of drugs, cosmetics, and food which are derived from plant cell and tissue cultures has a long tradition. The emerging trend of manufacturing cosmetics and food products in a natural and sustainable manner has brought a new wave in plant cell culture technology over the past 10 years. More than 50 products based on extracts from plant cell cultures have made their way into the cosmetics industry during this time, whereby the majority is produced with plant cell suspension cultures. In addition, the first plant cell culture-based food supplement ingredients, such as Echigena Plus and Teoside 10, are now produced at production scale. In this mini review, we discuss the reasons for and the characteristics as well as the challenges of plant cell culture-based productions for the cosmetics and food industries. It focuses on the current state of the art in this field. In addition, two examples of the latest developments in plant cell culture-based food production are presented, that is, superfood which boosts health and food that can be produced in the lab or at home

G-protein signaling: back to the future

Heterotrimeric G-proteins are intracellular partners of G-protein-coupled receptors (GPCRs). GPCRs act on inactive Gα·GDP/Gβγ heterotrimers to promote GDP release and GTP binding, resulting in liberation of Gα from Gβγ. Gα·GTP and Gβγ target effectors including adenylyl cyclases, phospholipases and ion channels. Signaling is terminated by intrinsic GTPase activity of Gα and heterotrimer reformation — a cycle accelerated by ‘regulators of G-protein signaling’ (RGS proteins). Recent studies have identified several unconventional G-protein signaling pathways that diverge from this standard model. Whereas phospholipase C (PLC) β is activated by Gαq and Gβγ, novel PLC isoforms are regulated by both heterotrimeric and Ras-superfamily G-proteins. An Arabidopsis protein has been discovered containing both GPCR and RGS domains within the same protein. Most surprisingly, a receptor-independent Gα nucleotide cycle that regulates cell division has been delineated in both Caenorhabditis elegans and Drosophila melanogaster. Here, we revisit classical heterotrimeric G-protein signaling and explore these new, non-canonical G-protein signaling pathways

Transcription activation in cells lacking TAFIIS

The general transcription factor TFIID is composed of the TATA-box-binding protein (TBP) and a set of TBP-associated factors (TAFIIs). In vitro, TAFIIs are required for activated transcription, and have been proposed to be obligatory targets of transcriptional activator proteins (activators)2. The function of TAFIIs has not been investigated systematically in vivo. A Saccharomyces cerevisiae TAFII complex (yTAFII complex) has been identified that shares functional and structural similarities with higher eukaryotic TFIID. In particular, most yTAFIIs are the homologue of a higher eukaryotic TAFII. Here we report that inactivation or depletion of six different yTAFIIs, including the core yTAFII, that contacts TBP, does not compromise transcriptional activation. We conclude that in vivo, activated transcription of many genes can occur in the absence of functional yTAFIIS, and that in these instances another transcription component(s) must be the target of the activator

Yeast TAFIIS in a multisubunit complex required for activated transcription

In higher eukaryotes the RNA polymerase II transcription factor TFIID is composed of a TATA-box-binding protein (TBP) and a set of tightly bound polypeptides, designated TBP-associated factors (TAFIIS). One or more TAFIIS are coactivators that are required for activated but not basal transcription. The eukaryotic transcription machinery is highly conserved and it is therefore puzzling that TAFIIS have not been identified in yeast. Here we use TBP as a protein-affinity ligand to isolate from yeast a multisubunit complex that is required specifically for activated transcription by RNA polymerase II. Microsequence analysis and cloning of two subunits of this complex reveal that they are the homologues of known mammalian and Drosophila TAFIIS. The genes encoding these two yeast TAFIIS are essential, suggesting that activated transcription is required for viability of Saccharomyces cerevisiae