title: Characterization of spermidine hydroxycinnamoyl transferases from eggplant (Solanum melongenaL.) and its wild relativeSolanum richardiiDunal.
abstract: Eggplant produces a variety of hydroxycinnamic acid amides (HCAAs) that have an important role in plant development and adaptation to environmental changes. In this study, we identified and characterized a spermidine hydroxycinnamoyl transferase (SHT) from eggplant (Solanum melongena) and its wild relativeS. richardii, designated asSmSHTandSrSHT, respectively.SmSHTwas abundant in flowers and fruits, whereas the level ofSrSHTwas remarkably low in all tissues. Heat-shock/drought treatment stimulated the expression ofSmSHTin both leaves and fruits, indicating its involvement in plant stress response. Both SHT polypeptides had extremely high identity with just five amino-acid substitutions. Recombinant SmSHT catalyzed the synthesis of mono-, bi- and tri- acylated polyamines. Using caffeoyl-CoA as the acyl donor, SmSHT preferred spermidine as the acyl acceptor. When spermidine was the acyl acceptor, the donor preference order for SmSHT was caffeoyl-CoA>feruloyl-CoA>ρ-coumaroyl-CoA. SrSHT exhibited the same substrate specificity as SmSHT, yet exhibited significantly higher catalytic activity than SmSHT. For example, under caffeoyl-CoA and spermidine,Kcatof SrSHT was 37.3% higher than SmSHT. Molecular modeling suggests that five amino-acid substitutions in SrSHT result in four alterations in their predicted 3D structures. In particular, the conserved Lys402 adjacent to the DFGWG motif, and Cys200 in the crossover loop in SmSHT were replaced by Glu and Ser in SrSHT. These substitutions may contribute to the enhanced activity in SrSHT. Our study provides a platform to generate HCAA rich fruits for eggplant and other solanaceous crops.
authors.affiliation: Food Quality Laboratory, Beltsville Agricultural Research Center, Agricultural Research Service of U.S. Department of Agriculture, Beltsville, MD 20705, USA; Horticulture & Landscape College, Hunan Agricultural University, Changsha 410128, Hunan, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Peng
authors.affiliation: Food Quality Laboratory, Beltsville Agricultural Research Center, Agricultural Research Service of U.S. Department of Agriculture , Beltsville, MD 20705, USA.
authors.forename: Tianbao
authors.initials: T
authors.lastname: Yang
authors.affiliation: Food Quality Laboratory, Beltsville Agricultural Research Center, Agricultural Research Service of U.S. Department of Agriculture , Beltsville, MD 20705, USA.
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Whitaker
authors.affiliation: Food Quality Laboratory, Beltsville Agricultural Research Center, Agricultural Research Service of U.S. Department of Agriculture , Beltsville, MD 20705, USA.
authors.forename: Frances
authors.initials: F
authors.lastname: Trouth
authors.affiliation: Food Quality Laboratory, Beltsville Agricultural Research Center, Agricultural Research Service of U.S. Department of Agriculture, Beltsville, MD 20705, USA; College of Horticulture, Nanjing Agricultural University, Nanjing 210095, Jiangsu, China.
authors.forename: Lingfei
authors.initials: L
authors.lastname: Shangguan
authors.affiliation: Food Quality Laboratory, Beltsville Agricultural Research Center, Agricultural Research Service of U.S. Department of Agriculture, Beltsville, MD 20705, USA; Department of Plant Science, University of Tennessee, Knoxville, TN 37996, USA.
authors.forename: Wen
authors.initials: W
authors.lastname: Dong
authors.affiliation: Food Quality Laboratory, Beltsville Agricultural Research Center, Agricultural Research Service of U.S. Department of Agriculture , Beltsville, MD 20705, USA.
authors.forename: Wayne M
authors.initials: WM
authors.lastname: Jurick