Genetic analysis of phytoene synthase 1 (Psy1) gene function and regulation in common wheat.

Shengnan Zhai,Genying Li,Yulian Li,Zhonghu He,Xianchun Xia,Jihu Li,Jianmin Song,Guoqi Song,Youwei Sun,Hongqing Ling

doi:10.1186/s12870-016-0916-z

Abstract

BackgroundPhytoene synthase 1 (PSY1) is the most important regulatory enzyme in carotenoid biosynthesis, whereas its function is hardly known in common wheat. The aims of the present study were to investigate Psy1 function and genetic regulation using reverse genetics approaches.ResultsTranscript levels of Psy1 in RNAi transgenic lines were decreased by 54–76 % and yellow pigment content (YPC) was reduced by 26–35 % compared with controls, confirming the impact of Psy1 on carotenoid accumulation. A series of candidate genes involved in secondary metabolic pathways and core metabolic processes responded to Psy1 down-regulation. The aspartate rich domain (DXXXD) was important for PSY1 function, and conserved nucleotides adjacent to the domain influenced YPC by regulating gene expression, enzyme activity or alternative splicing. Compensatory responses analysis indicated that three Psy1 homoeologs may be coordinately regulated under normal conditions, but separately regulated under stress. The period 14 days post anthesis (DPA) was found to be a key regulation node during grain development.ConclusionThe findings define key aspects of flour color regulation in wheat and facilitate the genetic improvement of wheat quality targeting color/nutritional specifications required for specific end products.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0916-z) contains supplementary material, which is available to authorized users.

Highlights

Phytoene synthase 1 (PSY1) is the most important regulatory enzyme in carotenoid biosynthesis, whereas its function is hardly known in common wheat
Phytoene synthase 1 (Psy1) gene expression and yellow pigment content (YPC) in grains of transgenic lines The 460 bp trigger fragment from Psy-A1 that was used for the RNA interference (RNAi) vector construction shared 90 % and 95 % sequence similarity with Psy-B1 and Psy-D1, respectively
The RNAi-mediated downregulation of Psy1 resulted in remarkable reduction in YPC, confirming the important impact of Psy1 on carotenoid accumulation in wheat grains

Summary

Introduction

Phytoene synthase 1 (PSY1) is the most important regulatory enzyme in carotenoid biosynthesis, whereas its function is hardly known in common wheat. Common wheat (Triticum aestivum L.) is a major cereal crop, supplying significant amounts of dietary carbohydrate and protein for over 60 % of the world population. It is an Phytoene synthase (PSY) catalyzes a vital step in carotenoid biosynthesis, generally recognized as the most important regulatory enzyme in the pathway [1, 6]. The wheat Psy gene was cloned based on the sequence homology, and QTL analysis showed that Psy co-segregated with yellow pigment content (YPC), which is significantly related to carotenoids (r = 0.8) [6, 9]. Several studies have focused on homology-based cloning of Psy and QTL analysis, whereas gene function and regulation remain to be determined

Objectives

Methods

Results

Discussion

Conclusion