| Food shortages are becoming one of the most serious global problems of this century due to the increasing population and the reduction of arable land.As an important component of wheat production,grain weight is a hot spot in recent years.At present,the TaGW2-6A gene has been successfully cloned in wheat,and its "T" base insertion mutation can significantly increase the grain width and grain weight of wheat.In this study,CS and NIL31 were used to study the effects of Ta GW2-6A on the development of grain from cytological level,grain filling and gene expression.The main findings are as follows:1.The grain filling rate and dry matter accumulation rate of wheat were closely related to grain weight.The fresh weight and dry weight of the endosperm of NIL31 were significantly higher than those of CS at 9 days after anthesis,and reached 46.04% and 48.71% at 35 days after anthesis,respectively.At the same time,the filling rate of NIL31 was significantly higher than that of CS,especially 9-20 days after anthesis.Compared with CS,the grain width,grain thickness and grain length of NIL31 increased by about 20%,13.6% and 12.9% respectively,and the grain weight increased by about 47.9%.These results indicate that TaGW2-6A allelic variation may control the grain size by influencing the grain filling and dry matter accumulation rate.2.With the development of endosperm,the length and width of CS and NIL31 central endosperm cells increased gradually from 3 to 25 days after anthesis,but NIL31 cells increased significantly compared with CS,especially 9-15 days after anthesis.At the same time,the cell proliferation rate of NIL31 was also significantly higher than that of CS.In addition,the seed coat of CS is thicker and denser than NIL31,which may limit the growth of endosperm cells and limit the expansion of the strength.Therefore,we speculate that TaGW2-6A allelic variation may be through the endosperm proliferation and the structure of epidermal cells,which ultimately affect the size of the seed.3.Cytokinin synthesis genes and cytokinin degradation genes can promote the accumulation of cytokinins,which in turn affect cell division.The results of qRT-PCR showed that the expression patterns of cytokinin synthesis genes TaIPT2,TaIPT3,TaIPT5 and TaIPT8 in NIL31 were similar to those of CS,but the transcription level of each gene was significantly higher than that of CS.In contrast to TaIPTs,the transcription levels of the cytokinin degradation genes TaCKX1,TaCKX2 and TaCKX6 were significantly higher in CS than in NIL31.Therefore,we speculate that the high expression of cytokinin synthesis gene and the low expression of cytokinin degradation gene in NIL31 lead to the increase of the number of grain cells,the increase of volume and the increase of grain filling rate,and finally lead to the formation of large grains.4.The synthesis of starch directly affected the grain filling of wheat,and its synthesis was regulated by negative regulator SPA and TaRSR1 and starch synthesis gene TaAGPL and TaAGPS.The transcription level of the starch synthase gene TaAGPL and TaAGPS in NIL31 was significantly higher than that in CS from 6 to 15 days after anthesis.SPA and TaRSR1 were overexpressed in CS and low in NIL31.Therefore,it is speculated that TaGW2-6A allele variation may affect the synthesis and accumulation of starch in NIL31 by affecting the expression of genes related to starch synthesis,and ultimately affect the grain size.In summary,TaGW2-6A allele may regulate the expression of cytokinin and starch-related genes through ubiquitin proteasome pathway,and promote the division of endosperm cells and the accumulation of starch to cause the formation of large grains. |
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