Molecular Mechanism Of Fructan Accumulation And Carbon Distribution In Hybrid Barley Grains

Fructan is recognized as a dietary fiber beneficial to human health.On Earth,over 36 000 species of plants produce fructan,including important cereal crops,for example,wheat and barley.High fructan content in the grain of cereal crops is an important trait for healthy human food production.However,it is difficult to raise the fructan content in harvested grain by breeding,because fructan can be easily degraded and mobilized during grain development.Here,we used natural variations of a transcription factor and reduced fructan hydrolytic activity in hybrids,with traditional crossbreeding methods combined with modern molecular breeding technologies,we achieved barley lines with over 11% storage fructan in the harvested grain,which was much higher than 0.5% ? 4% in ordinary barley.Furthermore,the relationship between the phenotype of the grain and the content of fructan,and the mechanism of carbon distribution were further studied.The main results of this study are as follows:1)The law of fructan accumulation in barley grain was,in the early stage,the expression of negative regulatory factor SUSIBA1 in fructan synthesis was low,and the synthesis activity was high.In the middle and late stage,the expression of SUSIBA1 was high,and the degradation activity was high,the degradation of fructan was rapid and massive.2)According to the dynamics of SUSIBA1 negative regulation transcripts and main synthetase gene and degradation enzyme gene expression characteristics of different developmental stages in barley seeds,we designed a breeding strategy,Cross the barley which with a higher fructan synthetic activity at early stage and a lower fructan hydrolytic activity at late stage,we got a hybrid barley with over 11% of fructan content.It was found and verified that the content of fructan in the seed of round barley was lower and that in the seed of flat barley was higher.3)Analysis of the fructan gene expression of the hybrid lines compare with the parents in different development stages of seeds revealed that the hybrid lines had inherited the high synthesis activity and low degradation activity of the parents.The homozygous hybrid lines were obtained,and the high fructan character could be inherited stably,and passed the field test.4)The law of ?-glucan accumulation in barley seeds was higher and higher during the developmental period.But its correlation r with fructan reached 0.9202.That is,which parts has a high content of fructan in seed,the ?-glucan content also high.The increased accumulation of fructan and ?-glucan is mainly in the endosperm of seeds.5)The seed germination test showed that the seed vigor of barley with high fructan content was significantly better than that with low fructan content.6)In this study,tillers and grain weight(Yield characters)of mature grains of high-fructan barley were not reduced.