AUTHOR=Zhou Hanchen , Wang Shijie , Xie Hao-Fen , Liu Guofeng , Shamala Lubobi Ferdinand , Pang Jingyi , Zhang Zhengzhu , Ling Tie-Jun , Wei Shu 

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

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.833682

DOI=10.3389/fpls.2022.833682

ISSN=1664-462X

ABSTRACT=<p>Geraniol is a potent tea odorant and exists mainly as geranyl glycoside in <italic>Camellia sinensis</italic>. 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 (<italic>GES</italic>) genes (<italic>CsTPS</italic>) and two Nudix hydrolase genes (<italic>CsNUDX1-cyto</italic> and <italic>CsNUDX1-chlo</italic>) 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 geranyl <italic>β</italic>-primeveroside were dramatically higher than those of geranyl <italic>β</italic>-glucoside, while free geraniol was undetectable in this study. A tempo-spatial variation of geranyl <italic>β</italic>-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) <italic>in vitro</italic> than did chloroplastidial CsNUDX1-chlo. A transgenic study revealed that expression of <italic>CsNUDX1-cyto</italic> resulted in significantly more geranyl <italic>β</italic>-primeveroside in transgenic <italic>Nicotiana benthamiana</italic> compared with non-transgenic wild-type, whereas expression of <italic>CsNUDX1-chlo</italic> had no effect. An antisense oligo-deoxynucleotide study confirmed that suppression of <italic>CsNUDX1-cyto</italic> transcription in tea shoots led to a significant decrease in geranyl <italic>β</italic>-primeveroside abundance. Additionally, <italic>CsNUDX1-cyto</italic> transcript levels and geranyl <italic>β</italic>-primeveroside abundances shared the same tempo-spatial patterns in different organs in the tea cultivar “Shucha Zao,” indicating that <italic>CsNUDX1-cyto</italic> is important for geranyl <italic>β</italic>-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 transgenic <italic>N. benthamiana</italic>. All our data indicated that <italic>CsNUDX1-cyto</italic> is involved in geranyl <italic>β</italic>-primeveroside production in tea plants. Our speculation about possible conversion from the chemical product of CsNUDX1-cyto to geranyl <italic>β</italic>-primeveroside in plants was also discussed.</p>