Shengnan Zhai1, Genying Li2, Youwei Sun1, Jianmin Song2, Jihu Li1, Guoqi Song2, Yulian Li2, Hongqing Ling3, Zhonghu He4,5, Xianchun Xia6. 1. Institute of Crop Science, National Wheat Improvement Center, Chinese Academy of Agricultural Sciences (CAAS), 12 Zhongguancun South Street, Beijing, 100081, China. 2. Crop Research Institute, Shandong Academy of Agricultural Sciences, 202 Gongye Bei Road, Jinan, Shandong, 250100, China. 3. State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China. 4. Institute of Crop Science, National Wheat Improvement Center, Chinese Academy of Agricultural Sciences (CAAS), 12 Zhongguancun South Street, Beijing, 100081, China. zhhecaas@163.com. 5. International Maize and Wheat Improvement Center (CIMMYT) China Office, c/o CAAS, 12 Zhongguancun South Street, Beijing, 100081, China. zhhecaas@163.com. 6. Institute of Crop Science, National Wheat Improvement Center, Chinese Academy of Agricultural Sciences (CAAS), 12 Zhongguancun South Street, Beijing, 100081, China. xiaxianchun@caas.cn.
Abstract
BACKGROUND: Phytoene 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. RESULTS: Transcript 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. CONCLUSION: The 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.
BACKGROUND: Phytoene 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. RESULTS: Transcript 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. CONCLUSION: The 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.