The reporter learned from the Chinese Academy of Agricultural Sciences that the crop molecular breeding technology and application innovation team of the Institute of Crop Science of the Academy of Sciences, together with Henan Agricultural University, identified the key gene ZMNAC78 that regulates iron into corn grains, and analyzed for the first time that the gene and metal transporters jointly form a molecular switch to control the molecular mechanism of iron entering corn grains, in order to solve the "hidden hunger"—— The deficiency of trace elements such as iron provides new genes, which provides theoretical and technical support for the cultivation of crop varieties with high yield and nutritional synergy. The findings were published in Science on Dec. 8**.
The use of this gene can increase the iron content of corn kernels to 70 per kilogram5 mg, which is twice the average iron content of corn kernels used in existing production. At the same time, the developed molecular markers can be used to breed new maize lines with high yields and rich iron grains. * Corresponding author Li Wenxue, researcher at the Institute of Crop Science, Chinese Academy of Agricultural Sciences, said.
About one-third of the world's population is affected by anemia caused by iron deficiency, and according to the data of the Fourth National Nutrition Survey, the prevalence of anaemia among Chinese residents is 201%, half of whom are iron deficiency anemia. Although iron supplements can be used to improve iron status, the cost is high. Increasing the iron content of daily food crops can help to improve iron nutrition status in a wide range of people at a fundamental and low cost, especially in developing countries where maize is a staple food.
In general, the iron content of maize grains is negatively correlated with yield, which greatly limits the development of new maize varieties that are both high yield and rich in iron. In 2004, the Consultative Group on International Agricultural Research (CGIAR) set up the "Bioaugmentation Challenge Project", and great progress has been made in rice, but due to the different grain structure of corn, the biological pathways of nutrients such as iron into it have always been an unsolved problem in the field of plant nutrition.
In this study, the researchers used 273 maize inbred line genotype data combined with 6 extreme material transcriptome data to identify a candidate gene, zmnac78, which is involved in regulating the iron content of maize grains. ZMNAC78 is highly expressed in the endosperm 16-24 days after corn pollination, which is also the period of rapid accumulation of nutrients in corn grains. Corn grains overexpressing this gene had an iron content of 70 per kilogram5 mg, which is significantly higher than the target of 60 mg/kg of iron content in corn kernels set by the Bioaugmentation Challenge Project for maize.
The researchers further elucidated the molecular pathways of how iron enters the corn kernel. The results showed that Zmnac78 was predominantly expressed in maize kernel basal endosperm delivery cells, the only interface for maize nutrients to enter the progeny, and could directly activate the metal ion transporter. The results showed that these metal transporters played an important role in the pathway of iron into maize grains, and it was clear that in basal endosperm transfer cells, ZMNAC78 and metal transporters together formed a molecular switch to control the transport pathway of iron into maize grains.
This study not only unravels the biological pathway of iron into corn grains, but also provides new ideas for analyzing how nutrients enter cereal crops with delivery cells such as wheat.