TaGW2, a Good Reflection of Wheat Polyploidization and Evolution.
Hexaploid wheat consists of three subgenomes, namely, A, B, and D. These well-characterized ancestral genomes also exist at the diploid and tetraploid levels, thereby rendering wheat as a good model species for studying polyploidization. Here, we performed intra- and inter-species comparative analyses of wheat and its relatives to dissect polymorphism and differentiation of theTaGW2genes. Our results showed that genetic diversity ofTaGW2decreased with progression from the diploids to tetraploids and hexaploids. The strongest selection occurred in the promoter regions ofTaGW2-6AandTaGW2-6B. Phylogenetic trees clearly indicated thatTriticum urartuandAe. speltoideswere the donors of the A and B genomes in tetraploid and hexaploid wheats. Haplotypes detected among hexaploid genotypes traced back to the tetraploid level.Fstand π values revealed that the strongest selection onTaGW2occurred at the tetraploid level rather than in hexaploid wheat. This infers that grain size enlargement, especially increased kernel width, mainly occurred in tetraploid genotypes. In addition, relative expression levels ofTaGW2ssignificantly declined from the diploid level to tetraploids and hexaploids, further indicating that these genes negatively regulate kernel size. Our results also revealed that the polyploidization events possibly caused much stronger differentiation than domestication and breeding.
Crop Genomics and Bioinformatics Center and National Key Lab of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural UniversityNanjing, China; Key Laboratory of Crop Gene Resources and Germplasm Enhancement, Ministry of Agriculture/The National Key Facility for Crop Gene Resources and Genetic Improvement/Institute of Crop Science, Chinese Academy of Agricultural SciencesBeijing, China.
Lin
L
Qin
Key Laboratory of Crop Gene Resources and Germplasm Enhancement, Ministry of Agriculture/The National Key Facility for Crop Gene Resources and Genetic Improvement/Institute of Crop Science, Chinese Academy of Agricultural Sciences Beijing, China.
Junjie
J
Zhao
Key Laboratory of Crop Gene Resources and Germplasm Enhancement, Ministry of Agriculture/The National Key Facility for Crop Gene Resources and Genetic Improvement/Institute of Crop Science, Chinese Academy of Agricultural Sciences Beijing, China.
Tian
T
Li
Key Laboratory of Crop Gene Resources and Germplasm Enhancement, Ministry of Agriculture/The National Key Facility for Crop Gene Resources and Genetic Improvement/Institute of Crop Science, Chinese Academy of Agricultural Sciences Beijing, China.
Jian
J
Hou
Crop Genomics and Bioinformatics Center and National Key Lab of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural UniversityNanjing, China; Key Laboratory of Crop Gene Resources and Germplasm Enhancement, Ministry of Agriculture/The National Key Facility for Crop Gene Resources and Genetic Improvement/Institute of Crop Science, Chinese Academy of Agricultural SciencesBeijing, China.
Xueyong
X
Zhang
Key Laboratory of Crop Gene Resources and Germplasm Enhancement, Ministry of Agriculture/The National Key Facility for Crop Gene Resources and Genetic Improvement/Institute of Crop Science, Chinese Academy of Agricultural Sciences Beijing, China.
Chenyang
C
Hao
TaGW2; Triticum aestivum; genetic differentiation; grain size; nucleotide polymorphism