A conserved strategy of chalcone isomerase-like protein to rectify promiscuous chalcone synthase specificity

Abstract

Land plants produce diverse flavonoids for growth, survival, and reproduction. Chalcone synthase is the first committed enzyme of the flavonoid biosynthetic pathway and catalyzes the production of 2′,4,4′,6′-tetrahydroxychalcone (THC). However, it also produces other polyketides, including p-coumaroyltriacetic acid lactone (CTAL), because of the derailment of the chalcone-producing pathway. This promiscuity of CHS catalysis adversely affects the efficiency of flavonoid biosynthesis, although it is also believed to have led to the evolution of stilbene synthase and p-coumaroyltriacetic acid synthase. In this study, we establish that chalcone isomerase-like proteins (CHILs), which are encoded by genes that are ubiquitous in land plant genomes, bind to CHS to enhance THC production and decrease CTAL formation, thereby rectifying the promiscuous CHS catalysis. This CHIL function has been confirmed in diverse land plant species, and represents a conserved strategy facilitating the efficient influx of substrates from the phenylpropanoid pathway to the flavonoid pathway.

Proanthocyanidin Biosynthesis—a Matter of Protection

“…The role of metabolons in reactions specific for PA biosynthesis, as suggested in Figure 2, requires further investigation. It is now well established that the earlier reactions in the flavonoid pathway are organized in metabolons anchored to the endoplasmic reticulum through association with the cytochrome P450 enzymes of the pathway (Nakayama et al, 2019;Waki et al, 2020), but physical interactions between the later enzymes of the pathway have yet to be demonstrated. The need for such physical organization of the pathway would appear necessary to explain the differentiation of starter unit from extension unit synthesis using shared enzymes (Jun et al, 2018).…”

PR10/Bet v1‐like Proteins as Novel Contributors to Plant Biochemical Diversity

“…Alternatively, NISO might interact with COR in a way that allows it to preferentially deliver codeinone to the active site for reduction. Yet another explanation might be analogous to the recently discovered protein–protein interactions between chalcone synthase (CHS) and chalcone isomerase‐like proteins, in which the interaction “rectifies” the promiscuous CHS enzyme activity in favor of a biologically relevant product [103] …”

Transcriptional profiling reveals conserved and species-specific plant defense responses during the interaction of the early divergent plantPhyscomitrium patenswithBotrytis cinerea

“…However, unlike angiosperms, P. patens does not seem to contain enzymes required for the synthesis of flavonones and flavones. Both CHIs are enhancers of flavonoid production genes encoding type IV CHI proteins with no CHI activity (Ngaki et al 2012;Waki et al 2020), and there are no evident orthologs for F3H and FLS (Koduri et al 2010;Kawai et al 2014). Thus, P. patens probably lacks the later steps in flavonoid biosynthesis, in contrast to M. polymorpha, which accumulates different types of flavonoids (Albert et al 2018).…”