Browse Articles

Article|07 Dec 2016|OPEN
Characterization of spermidine hydroxycinnamoyl transferases from eggplant (Solanum melongena L.) and its wild relative Solanum richardii Dunal
Hui Peng1,2 , Tianbao Yang1 , , Bruce D Whitaker1 , , Frances Trouth1 , Lingfei Shangguan1,3 , Wen Dong1,4 , Wayne M Jurick,1
1Food Quality Laboratory, Beltsville Agricultural Research Center, Agricultural Research Service of U.S. Department of Agriculture, Beltsville, MD 20705, USA
2Horticulture & Landscape College, Hunan Agricultural University, Changsha 410128, Hunan, China
3College of Horticulture, Nanjing Agricultural University, Nanjing 210095, Jiangsu, China
4Department of Plant Science, University of Tennessee, Knoxville, TN 37996, USA
*Corresponding author. E-mail: tianbao.yang@ars.usda.gov,bruce.whitaker@ars.usda.gov

Horticulture Research 3,
Article number: 62 (2016)
doi: https://doi.org/10.1038/hortres.2016.62
Views: 682

Received: 01 Jul 2016
Revised: 30 Oct 2016
Accepted: 30 Oct 2016
Published online: 07 Dec 2016

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 relative S. richardii, designated as SmSHT and SrSHT, respectively. SmSHT was abundant in flowers and fruits, whereas the level of SrSHT was remarkably low in all tissues. Heat-shock/drought treatment stimulated the expression of SmSHT in 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, Kcat of 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.