Natural Variation Analysis Of Zinc Content In Maize Kernel And Candidate Gene Identification

Zinc(Zn)is an essential nutrition element for human body.Low levels of zinc in cereals,the staple food of the developing world,contribute to zinc malnutrition in nearly 2 billion people worldwide.Zinc is also an essential trace element in plants and plays an irreplaceable role.Therefore,the study of the transport and accumulation of zinc in seeds is the only way for us to use technical means to modify the zinc content in food for biofortification.Maize is one of the three most important food crops in the world,and is also the main food for most livestock.The content of nutrients in maize is related to the health of many organisms.Current studies have reported the general distribution of different nutrient elements in maize kernels.However,the mechanism of transport and accumulation of these mineral elements was less studied.Zinc as one of the important trace elements,finding the genes regulating zinc content in maize kernels and studying the molecular mechanism of zinc transport and accumulation in maize kernels will provide theoretical guidance and genetic resources for the cultivation of new zinc-rich maize varieties.Based on genome-wide association analysis of Zn content in mature kernels of CUBIC population,we identified a major QTL on chromosome 5 and named a potential gene,HIZ,which was specifically expressed in Basal endosperm transfer layer(BETL)of maize kernels at 10 days after pollination.Haplotype analysis showed that the difference of expression level caused by HIZ promoter sequence variation was the reason for the variation of zinc content in grain of natural population.The results of XRF and ICP-MS showed that the content of zinc in mature kernels of HIZ mutant was significantly lower than that of wild type.Zinc in HIZ mutants is restricted to BETL during seed development.The seeds of HIZ mutants also showed a phenotype of increased silty starch and decreased the number of starch grains,indicating that zinc content played an important role in controlling the quality of maize starch.In this study,we found that HIZ specifically regulates the transport and accumulation of zinc in maize kernels and thus participates in maize kernels development and regulates the endosperm starch synthesis.