Soybean chalcone isomerase: evolution of the fold, and the differential expression and localization of the gene family

Reference Report for RTN20170505.1

Title:	Soybean chalcone isomerase: evolution of the fold, and the differential expression and localization of the gene family
Authors:	Dastmalchi, M., Dhaubhadel, S.
Source:	Planta 2015, 241:507-523
Abstract:	The phenylpropanoid pathway produces a diverse array of plant natural products. A key branch-point enzyme, chal- cone isomerase, catalyzes the reaction producing flava- nones, the backbone for many downstream metabolites such as flavonoids and isoflavonoids. We have identified twelve soybean GmCHIs that fall into four subfamilies. The study of this family in soybean in the context of var- ious CHIs and CHI-like proteins, across divisions in the plant kingdom and beyond, shows an evolutionary journey from fatty acid-binding proteins (FAPs) to sterically restricted folds that gave rise to the chalcone-to-flavanone isomerase. There are four GmCHIs with this functionality, three of which belong to a legume-specific clade known as Ôtype IIÕ CHIs. Tissue-specific expression of eight core members of the soybean CHI family showed differential temporal and spatial expression, pointing to the potential function of GmCHI1A in seed isoflavonoid production. Promoter analysis of the GmCHIs described the minutiae of sub-organ expression patterns. Subcellular localization of the family was conducted to investigate the possibility of pathway-specific compartmentalization. Subfamilies 1, 2 and 4 localized to the nucleus and cytoplasm, with nuclear localization of CHIs raising questions about alternate function. GmCHI3 isoforms localized to the chloroplast, which, in conjunction with their position on the phyloge- netic tree and expression patterns, closely associates them with the FAPs. This study provides the first comprehensive look at soybean CHIs, a family of unique evolutionary background and biochemical function, with the catalyti- cally active members producing the backbone substrate in an important plant metabolic pathway.

Funded by the USDA-ARS. Developed by the USDA-ARS SoyBase and Legume Clade Database group at the Iowa State University, Ames, IA

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