| Flour color-related traits, including L*, a*,b* and yellow pigment content (YPC), are important parameters influencing the quality of wheat end-use products and have become an important target for wheat quality improvement. Previous studies mostly focused on QTL analysis, gene cloning and molecular marker development, whereas the function and genetic regulation of Psyl gene, the key gene associated with flour color, are not well investigated. Due to the limiting mapping populations and molecular markers used previously, a lot of genes for flour color-related traits have not been detected. Therefore, the aims of this study were to (1) identify QTL for flour color-related traits and characterize candidate genes using a common wheat recombinant inbred line (RIL) population derived from a cross between Gaocheng 8901 and Zhoumai 16 and 247 common wheat cultivars, and (2) illuminate the function and genetic regulation of Psyl gene by complementary approaches (RNAi, RNA-Seq and TILLING). The main results were as follows:1. The Gaocheng 8901/Zhoumai 16 RILs were genotyped by the wheat 90K iSelect array. A high-density genetic linkage map was constructed based on 2,205 skeleton markers, and 26 linkage groups representing all 21 wheat chromosomes were identified. The whole linkage map covered 2859.2 cM, with an average chromosome length of 136.2 cM, and the overall genetic density was 1.3 cM. Fifty-two QTL for flour color-related traits were identified and mapped on homoeologous groups 1,2,5 and 7 chromosomes, and chromosomes 3B,4A,4B and 6B. Compared with previous studies, five QTL for a*, two for b*, one for L* and one for YPC were new. Seven candidate genes related to flour color-related traits were identified, one for Pinb-Dl, and six others were involved in the terpenoid backbone biosynthesis pathway. The high-density genetic linkage map constructed by the wheat 90K iSelect array represents a useful tool to identify QTL for complex quantitative traits and candidate genes.2. A genome-wide association study (GWAS) for flour color-related traits was performed on 247 common wheat cultivars using the wheat 90K iSelect array. Nineteen associated loci for flour color-related traits were identified, and one for a* and one for L* were new. Six candidate genes related to flour color-related traits were identified, including Pinb-D1, Psy-Al, Psy-B1 and genes coding for NADP-dependent malic enzyme, cytosolic malate dehydrogenase and ascorbate peroxidase. A genome-wide association study based on the wheat 90K iSelect array was proven to be efficient and reliable for illustrating the molecular basis of complex quantitative traits.3. The transcript level of Psyl in RNAi transgenic lines were significantly decreased (54-76%), accompanied by the significant reduction of YPC (26-35%), confirming the impact of Psyl on YPC in wheat grains. Three transgenic lines (273-2A,275-3A and 279-1A) with most significantly reduced YPC were selected for RNA-Seq. Functional analysis indicated a series of candidate genes involved in secondary metabolic pathways and core metabolic processes work collaboratively for the Psyl down-regulation. Two EMS-mutagenised populations were screened for mutations in Psyl by TILLING.The aspartate rich domain (DXXXD) was an important region for PSY1 function and played a vital role in yellow pigment accumulation by regulating gene expression, changing enzyme activity and alternative splicing. Based on the analysis of Psyl expression in RNAi transgenic lines and EMS mutants,14 DPA was considered as a key regulation node for Psyl expression during wheat grain development. In addition, the EMS mutants with favorable traits would be important germplasm resources for the genetic improvement of flour color and nutritional quality. |
PDF Full Text Request