| Colored rice seeds are rich in natural pigments and various trace elements,that have antioxidant functions and the extremely high nutritional value.We got the iron-rich“Luotian Red Rice”that came from the local traditional resources.However,it was found that different regions and different environments for cultivation affected the stability of pigment appearance during planting.We used 9311 as the control material because of the growth period.By foliage spraying ferrous sulfate at the booting stage and heading stage,we hope solve the problem of pigment stability in red rice and explore the way of enhancing rice nutritional quality.By determining metabolites and trace elements in mature grains that analyzed the effects in accumulating trace elements and pigments by supplying exogenous iron.We got key genes involved in flavonoid synthesis and the genes for iron transport-related by RNA-Seq of developing grains during filling critical stage.And we validated the gene and protein expression of these key enzyme in developing grains during filling stage.Analysis of the characteristics of pigment metabolism and regulation of key enzyme expression in flavonoid pathway in grains,we have exploring the mechanism of pigment accumulation in rice under spraying FeSO4,which provided theoretical basis for improvement quality in“Luotian Red Rice”and provided reference for study excellent traits in other crops.In this study,we got these results:1.By metabonomics analysis,we confirmed characteristic pigment metabolites in RM1 are Gambiriin b3,Pavetannin b6,Catechin,Procyanidin b8,Procyanidin c1,3-?4-hydroxybenzoyl?epicatechin and so on.2.By cytological observation and measured pigment content,we found that it has a positive effect on pigment accumulation in red rice grains for foliar spraying ferrous sulfate.The mainly pigment is proanthocyanidin and it is accumulated on pericarp.According to pericarp appearance,it has less white space between cells and evenly colored in RM1 under 0.1%FeSO4.The content of OPC is increased significantly in flowering 15d to 25d under 0.1%FeSO4.In addition,metabolites were showed down-regulation in other branches of flavonoids synthesized by 0.1%FeSO4treatment,indicating that spray iron ion promoted the synthesis of proanthocyanidins,and provided sufficient substrate by decreasing other branched products.3.The iron content has increased by spraying FeSO4 and the effect of spraying0.2%FeSO4 is more significant.The iron content is 125.84 mg/kg and 159.18 mg/kg in RM1 and RM5 respectively.In addition,the content of VB55 and VE both are up-regulated in grains of RM1 under 0.1%FeSO4.It indicates that foliar application treatment has a positive impact on improving the nutritional quality in red rice,such as trace element.4.We got 6 key enzyme genes in flavonoid synthesis and 3 iron transport genes by RNA-Seq.The expression of target gene was verified by qPCR.It was found that the upstream genes CHS and F3H-3 were increased in the 5 days and 10 days after flowering in RM1 and RM5 under 0.1%FeSO4,and the downstream gene LAR was gradually increased in the filling medium stage.The expression of Fe-1 and MHX1are increased in caryopsis growth stages,indicating that proper foliar application could promote the synthesis of flavonoids and iron transport in red rice.The protein expression of CHS and LAR was maximum at flowering 20d and 25d respectively and significantly increased in RM1 and RM5 after 0.1%FeSO4.Supplying appropriate concentration of iron ions(0.1%Fe2+)can promote the expression of key enzymes in the flavonoid pathway of red rice in the late filling stage,which is benificial for accumulating and stable increasing proanthocyanidins.In summary,by foliar spraying FeSO4?0.1%?can effectively improve the pigment quality of colored rice and increase the iron content in the grains.So foliar spraying ferrous sulfate can be used as an economical and effective cultivation method to increase the iron content and pigment stability in rice grain. |
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