Cytosolic Nudix Hydrolase 1 Is Involved in Geranyl β-Primeveroside Production in Tea

Abstract

Geraniol is a potent tea odorant and exists mainly as geranyl glycoside inCamellia sinensis. Understanding the mechanisms of geraniol biosynthesis at molecular levels in tea plants is of great importance for practical improvement of tea aroma. In this study, geraniol and its glycosides from tea plants were examined using liquid chromatography coupled with mass spectrometry. Two candidate geraniol synthase (GES) genes (CsTPS) and two Nudix hydrolase genes (CsNUDX1-cytoandCsNUDX1-chlo) from the tea genome were functionally investigated through gene transcription manipulation and gene chemical product analyses. Our data showed that in tea leaves, levels of geranylβ-primeveroside were dramatically higher than those of geranylβ-glucoside, while free geraniol was undetectable in this study. A tempo-spatial variation of geranylβ-primeveroside abundance in tea plants existed, with high levels in young and green tissues and low levels in mature or non-green tissues. Cytosolic CsNUDX1-cyto showed higher hydrolysis activity of geranyl-pyrophosphate to geranyl-monophosphate (GP)in vitrothan did chloroplastidial CsNUDX1-chlo. A transgenic study revealed that expression ofCsNUDX1-cytoresulted in significantly more geranylβ-primeveroside in transgenicNicotiana benthamianacompared with non-transgenic wild-type, whereas expression ofCsNUDX1-chlohad no effect. An antisense oligo-deoxynucleotide study confirmed that suppression ofCsNUDX1-cytotranscription in tea shoots led to a significant decrease in geranylβ-primeveroside abundance. Additionally,CsNUDX1-cytotranscript levels and geranylβ-primeveroside abundances shared the same tempo-spatial patterns in different organs in the tea cultivar “Shucha Zao,” indicating thatCsNUDX1-cytois important for geranylβ-primeveroside formation in tea plants. Results also suggested that neither of the two candidate GES genes in tea plants did not function as GES in transgenicN. benthamiana. All our data indicated thatCsNUDX1-cytois involved in geranylβ-primeveroside production in tea plants. Our speculation about possible conversion from the chemical product of CsNUDX1-cyto to geranylβ-primeveroside in plants was also discussed.