Regulation Of Grain Length By The TaSnRK1-TaIBH1 Module In Bread Wheat

Wheat is one of the world’s top three food crops,feeding 40%of the population.With the increase in global food demand and the decrease in arable land,increasing wheat production is of great significance to China’s food security.Wheat yield is composed of the number of mu ears,the number of grains per ear and the weight of 1,000 grains.The 1000 grain weight is regulated by the grain length,grain size and filling fullness,which is a relatively high heritability quantitative trait.In previous study,our research group constructed a genetic linkage map associated with grain length of Chinese Spring and ShiXin828 by Specific-Locus Amplified Fragment Sequencing(SLAF-Seq).A key QTL site qGL2D located on the long arm of the chromosome 2D were obtained.The key gene TaIBHl-2D that regulates grain length and weight was identified by fining mapping and transcriptomic analysis.In this study,the methods of genetics,biochemistry,genomics and metabonomics were comprehensively used to analyze the molecular mechanism of TaIBH1-2D and its interacting protein TaSnRK1α1-1D regulating wheat grain length and grain weight.The specific results are as follows:1.The analysis of agronomic characters of TaIBH1-2D overexpression materials and gene knockout mutant Taibh1-2ABD-cr showed that the grain length of TaIBH1-2D overexpression materials was shortened and the 1000-grain weight was decreased,while Taibh1-2ABD-cr showed that the grain length and 1000-grain weight were significantly increased.Multivariate analysis showed that TaIBH1-2D inhibited the expression of cell elongation genes TaEXPA2 and TaEXPA4,inhibited the elongation and growth of seed coat cells,and shortened the grain length.On the other hand,TaIBH1-2D reduced the expression of TaSUT1,a key gene for long-distance transportation of sucrose,inhibited the outward transportation of sucrose from flag leaves,and reduced grain filling,which led to the decrease of 1000-grain weight.2.TaSnRK1α1-1D was found to be an interaction protein of TaIBH1-2D by yeast twohybrid library screening.The interaction between the two protein was verified by GST-pull down,protoplast bimolecular fluorescence complementation and CoIP in vivo and in vitro.Genetic analysis showed that the overexpression of TaSnRK1α1-1D promoted the elongation and growth of wheat seed coat cells,and increased the length and 1000-grain weight of wheat grain.RT-qPCR analysis showed that overexpression of TaSnRK1α1-1D promoted the expression of TaEXPA2,TaEXPA4 and TaSUT1.Metabolic analysis showed that the starch content in flag leaves decreased significantly and the sucrose content increased significantly in TaSnRK1α1-1D overexpression lines.These results indicate that TaSnRK1α1-1D can regulate wheat grain development by promoting cell elongation and grain filling.3.In vitro kinase experiments showed that TaSnRK1α1-1D could directly phosphorylate TaIBH1-2D.In vivo hybridization materials and cell-free semi-in vitro protein degradation experiments confirmed that TaSnRK1α1-1D reduced the protein stability of TaIBH1-2D and promoted its degradation.Taken together,this study revealed the underlying mechanism of TaIBH1-2D negatively regulating wheat grain development by inhibiting wheat grain seed coat cell elongation and sucrose source-sink transport in flag leaves.However,TaSnRK1α1-1D regulates the stability of TaIBH1-2D protein through phosphorylation and thereby promotes the development of wheat grain.Our study provided a superior allele and theoretical guidance for wheat yield breeding.