Research progress in maize one-way cross incompatibility in Institute of Genetic Development

　　Corn is one of the crops with the largest sown area and the highest yield in China. Corn has a wide range of uses, not only as feed, but also for various industrial purposes, and provides high-quality protein and starch for human beings. The natural outcrossing rate of maize is as high as 95%, so hybrid seed production and special maize production need to be strictly separated. Conventional time and space isolation measures are time-consuming, laborious and difficult. How to realize corn non-isolated production in a scientific way is an urgent production problem. In general, both self-pollination and hybridization of maize can bear fruit, but there is a phenomenon that a few maize do not accept other maize pollen in nature, which is called unilateral cross-incompatibility (UCI) of maize. Some studies have reported three UCI loci, Ga1, Ga2 and Tcb1, which are composed of pollen and filament determinants respectively. According to the structure and function of UCI loci, maize in nature can be divided into three types: S type (Ga1-S, Ga2-S and Tcb1-S), which contains both pollen and filament determinant genes; M-type (Ga1-M, Ga2-M and Tcb1-M) only contains pollen determinant genes; Common types (ga1, ga2 and tcb1) contain neither pollen nor filament determinant gene. UCI controls the sexual transmission direction of haploid gametes and can be used for reproductive isolation between different types of maize.　
　　Chen Huabang, research group of Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, devoted himself to the study of maize one-way cross incompatibility, and reported the pollen and filament factor genes at Ga1 and Ga2 loci and their applications successively (Zhang et al., 2012；; Zhang et al., 2018，Chen et al., 2022； Cai et al., 2022）。 Recently, the team has once again made important progress in the study of maize incompatibility. In this study, the pollen determinant Tcb-m at Tcb1 locus was cloned. This is the "last" cloned determinant gene of maize incompatibility system. So far, all the key determinants of the three incompatibility sites have been cloned and verified, which laid the foundation for the study of commonness and specificity among maize incompatibility systems. On November 16th, related research results were published online in Plant Biotechnology Journal with the title of A Pollen Expressed PME Gene at TC B1 Locus Confers Maize Independent Cross-in Compatibility.　
　　It was found that the pollen factor Tcb1-M at TCB1 locus of maize encoded Pectin Methylesterases (PME), which was specifically expressed in the pollen of Tcb1-S materials. Studies have shown that the expression of Tcb1-m gene in common corn by transgenic method can make it pollinate and bear fruit for Tcb1-S type materials. Tcb1 locus and Ga1 locus are closely linked, and their pollen and filament factors are highly similar, and the two loci are in tandem repetitive relationship. However, Tcb1 locus only exists in the primitive ancestor of maize, and Ga1 locus exists in both maize and maize, which indicates that the two loci have differentiated and produced specificity after maize domestication. There are also a certain number of materials containing Ga1 or Ga2 loci in common corn in nature, which will reduce the application value of UCI loci in corn. In this study, the materials containing three sites were combined in different forms, and a polymer material containing two or three incompatible sites was created, which not only effectively hindered the pollen of ordinary corn, but also effectively prevented the risk of penetration of materials containing a single incompatible site, and further improved the application of corn incompatibility in non-isolated seed production. This study laid a material foundation for the mechanism analysis of incompatible systems.　
　　The research work is supported by the National Natural Science Foundation of China.　
　　Cloning and application of pollen factor gene at Tcb1 locus in maize