Regulation of phytoalexin biosynthesis for agriculture and human health

Abstract

Phytoalexins are diverse secondary metabolites of plants that are biosynthesized transiently and in relatively low amounts in response to pathogens and certain abiotic stresses. They commonly have potent antimicrobial and medicinal activities. As such, scientists have attempted to increase their accessibility by inventing diverse in vitro and in vivo approaches. Among these approaches, bioengineering plant transcription factors that directly regulate phytoalexin biosynthesis genes may be the most promising. Recent research has identified conserved transcription factors that directly regulate distinct phytoalexin biosynthesis pathways in different plant species. The intriguing results provide new insight into how conserved defense signaling pathways in plants result in lineage-specific biochemical defenses.These recent findings also suggest that a common transcription factor network could be engineered to enhance the biosynthesis of different phytoalexins in plants. However, the picture is far from complete since one or more transcription factors required to fully activate phytoalexin biosynthesis remain unidentified, and the exact mechanism of how the conserved factors regulate diverse phytoalexin pathways remains to be clarified. Here we review the agricultural and medicinal importance of phytoalexins, recent approaches to increase their accessibility, and the mechanisms that plants employ to activate and limit their biosynthesis. This review contributes to providing a systems level understanding of the regulation of phytoalexin biosynthesis so that effective bioengineering strategies can be developed to enhance phytoalexin biosynthesis for medicine and agriculture.

Expanding the Phytoalexin Chemical Space: Tropalexins a and B from Tropaeolum Majus Suggest Evolutionary Conservation of Biosynthetic Enzymes

“…In addition, based on the current phylogenetic classification of Brassicales tribes (Guo et al, 2017;Koch and German, 2013) and the chemical structures of cruciferous phytoalexins of species belonging to those tribes (Pedras et al, 2011), we suggest that the primary precursors and intermediates of such pathways are similar within phylogenetically related tribes as for example, Brassicales phytoalexins contributes to the design of crops having higher resistance levels to microbial pathogens and abiotic stress (Ahmed and Kovinich, 2020).…”

De novo biosynthesis of bioactive isoflavonoids by engineered yeast cell factories

“…7c ), showing the application potential of our platform strain. Moreover, our work sheds light on the complete microbial biosynthesis of value-added isoflavonoids such as DEIN-derived legume phytoalexins 81 and may be applied in characterizing novel metabolic enzymes for the production of isoflavonoid derivatives. Additional improvements on the catalytic efficiency and specificity of key isoflavonoid biosynthetic enzymes through protein engineering 78 , directed pathway evolution facilitated by biosensor-mediated high-throughput screening as well as engineering of extracellular transport of isoflavonoids 82 , 83 , may further optimize the phenotypes of our platform strains, including higher titer/productivity and reduction/elimination of byproducts, to meet industrial-scale production requirements in the future.…”

Reflections on the intriguing occurrence of some recently isolated natural products as racemates and scalemic mixtures

“…In light of the continuing reports of new natural racemates, the conventional wisdom of the rarity of these metabolites must be reconsidered. Racemates appear to have evolved in an energy efficient pathway with unique structural and stereochemical features that provide a selective advantage in a predatory growth environment, not only to the producing organism but perhaps also to the host with regard to endophytic fungi 33–36 . It seems reasonable to postulate that both enantiomers could target nucleic acids, signaling proteins or enzymes of competitor organisms in a two for one scenario, or greater “payload” to use a military metaphore.…”