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Identification of chalcone isomerase in the basal land plants reveals an ancient evolution of enzymatic cyclization activity for synthesis of flavonoids
Author(s) -
Cheng AiXia,
Zhang Xuebin,
Han XiaoJuan,
Zhang YuYing,
Gao Shuai,
Liu ChangJun,
Lou HongXiang
Publication year - 2018
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.14852
Subject(s) - biology , selaginella , arabidopsis , bryophyte , physcomitrella patens , botany , chalcone , chalcone isomerase , arabidopsis thaliana , mutant , biochemistry , enzyme , gene , biosynthesis , chalcone synthase , stereochemistry , chemistry
Summary Flavonoids ubiquitously distribute to the terrestrial plants and chalcone isomerase ( CHI )‐catalyzed intramolecular and stereospecific cyclization of chalcones is a committed step in the production of flavonoids. However, so far the bona fide CHI s are found only in vascular plants, and their origin and evolution remains elusive. We conducted transcriptomic and/or genomic sequence search, subsequent phylogenetic analysis, and detailed biochemical and genetic characterization to explore the potential existence of CHI proteins in the basal bryophyte liverwort species and the lycophyte Selaginella moellendorffii . We found that both liverwort and Selaginella species possess canonical CHI ‐fold proteins that cluster with their corresponding higher plant counterparts. Among them, some members exhibited bona fide CHI activity, which catalyze stereospecific cyclization of both 6′‐hydroxychalcone and 6′‐deoxychalcone, yielding corresponding 5‐hydroxy and 5‐deoxyflavanones, resembling the typical type II CHI s currently known to be ‘specific’ for legume plants. Expressing those primitive bona fide CHI s in the Arabidopsis chi mutant restores the seed coat transparent testa phenotype and the accumulation of flavonoids. These findings, in contrast to our current understanding of the evolution of enzymatic CHI s, suggest that emergence of the bona fide type II CHI s is an ancient evolution event that occurred before the divergence of liverwort lineages.