A single silk-and multiple pollen-expressed PMEs at the Ga1 locus modulate maize unilateral cross-incompatibility

The Gametophyte factor1(Ga1) locus in maize confers unilateral cross-incompatibility(UCI), and it is controlled by both pollen and silk-specific determinants. Although the Ga1 locus has been reported for more than a century and is widely utilized in maize breeding programs, only the pollen-specific ZmGa1P has been shown to function as a male determinant;thus, the genomic structure of the Ga1 locus and all the determinants that control UCI at this locus have not yet been fully characterized.Here, we used map-based cloning to confirm the determinants of UCI at the Ga1 locus and maize pan-genome sequence data to characterize the genomic structure of the Ga1 locus. The Ga1 locus comprises one silk-expressed pectin methylesterase gene(PME, ZmGa1F) and eight pollenexpressed PMEs(ZmGa1P and ZmGa1PL1-7).Knockout of ZmGa1F in Ga1/Ga1 lines leads to the complete loss of the female barrier function. The expression of individual ZmGa1PL genes in a ga1/ga1 background endows ga1 pollen with the ability to overcome the female barrier of the Ga1 locus. These findings, combined with genomic data and genetic analyses, indicate that the Ga1 locus is modulated by a single female determinant and multiple male determinants, which are tightly linked.The results of this study provide valuable insights into the genomic structure of the Ga2 and Tcb1 loci and will aid applications of these loci in maize breeding programs.

玉米杂交不亲和性研究初探

利用国内发现的玉米杂交不亲和性材料Inco .1进行了正反交测交和回交试验 ,表明它不能接受除爆裂玉米外的任何一类玉米的花粉 ,因而果穗不结子 ,相反用它的花粉授到各类玉米花粉上 ,则能正常结子 ,说明它是一个单向杂交不亲和性材料 ,具有较强的花粉竞争优势 ,是由显性配子体基因Gas 控制的 ,这与国外认为所有的马齿玉米为ga因子控制的论点完全不同 ,是一个值得重视的遗传材料。