Chalcone isomerase-like genes in Tradescantia BNL4430: identification, molecular characterization, and differential expression profiles under Ɣ-radiation stress

Abstract

Chalcone isomerase (CHI) is an important catalytic enzyme that converts naringenin (chalcone) to (2S)-naringenin in phenylpropanoid pathway. Here, we performed the first comprehensive molecular genetic study on Chalcone isomerase genes in Tradescantia clone BNL 4430 (designated as TrCHI). We identified seven TrCHIs genes (five with full length and two with partial length) through in silico analysis using available transcriptomic resources. Phylogenetic analysis suggest that TrCHIs are closely related to rice CHI. TrCHIs fall into three different CHI subfamilies: (1) type I (TrCHI2 including TrCHI2a, 2b, 2c, and 2d), (2) type III (TrCHI3 including TrCHI3B and 3C), and (3) type IV (TrCHI4). These partial or full length TrCHI genes were 456–819 bp in length with molecular mass ranging from 23 kDa to 47 kDa. Type I (TrCHI2) subfamily has the conserved active substrate binding sites similar to previously reported CHIs. The predicted tertiary structures of TrCHI2b showed structural configurations consistent with AtCHIs, suggesting that type I (TrCHI2) subfamily members of CHI might have active roles in flavonoid production. Real-time quantitative polymerase chain reaction (qRT-PCR) revealed that TrCHIs were expressed in a tissue-specific manner. TrCHIs in flowers under Ɣ–radiation treatment were up-regulated, indicating their potential action against radiation stress. Their regulation might be correlated with the presence of a few cis elements in their promoters. Our results provided a basis for functional study of flower pigmentation and breeding for novel flower color. They will also help us to elucidate radiation signal transduction pathways in Tradescantia.