National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, 430070, China.
Hubei Hongshan Laboratory, Wuhan, 430070, China.
Nat Commun. 2022 Aug 3;13(1):4498. doi: 10.1038/s41467-022-32180-9.
Unilateral cross incompatibility (UCI) occurs between popcorn and dent corn, and represents a critical step towards speciation. It has been reported that ZmGa1P, encoding a pectin methylesterase (PME), is a male determinant of the Ga1 locus. However, the female determinant and the genetic relationship between male and female determinants at this locus are unclear. Here, we report three different types, a total of seven linked genes underlying the Ga1 locus, which control UCI phenotype by independently affecting pollen tube growth in both antagonistic and synergistic manners. These include five pollen-expressed PME genes (ZmGa1Ps-m), a silk-expressed PME gene (ZmPME3), and another silk-expressed gene (ZmPRP3), encoding a pathogenesis-related (PR) proteins. ZmGa1Ps-m confer pollen compatibility. Presence of ZmPME3 causes silk to reject incompatible pollen. ZmPRP3 promotes incompatibility pollen tube growth and thereby breaks the blocking effect of ZmPME3. In addition, evolutionary genomics analyses suggest that the divergence of the Ga1 locus existed before maize domestication and continued during breeding improvement. The knowledge gained here deepen our understanding of the complex regulation of cross incompatibility.
单侧交叉不亲和性（UCI）发生在爆米花玉米和硬质玉米之间，是物种形成的关键步骤。据报道，ZmGa1P 基因编码一个果胶甲酯酶（PME），是 Ga1 座位的雄性决定因子。然而，该座位的雌性决定因子以及雌雄决定因子之间的遗传关系尚不清楚。在这里，我们报道了 Ga1 座位下的三种不同类型，共七个连锁基因，它们通过独立地以拮抗和协同的方式影响花粉管生长来控制 UCI 表型。这些基因包括五个花粉表达的 PME 基因（ZmGa1Ps-m）、一个丝表达的 PME 基因（ZmPME3）和另一个丝表达的基因（ZmPRP3），分别编码一个与发病相关的（PR）蛋白。ZmGa1Ps-m 赋予花粉亲和性。ZmPME3 的存在导致丝拒绝不亲和花粉。ZmPRP3 促进不亲和花粉管生长，从而打破 ZmPME3 的阻断作用。此外，进化基因组学分析表明，Ga1 座位的分化发生在玉米驯化之前，并在育种改良过程中持续进行。这里获得的知识加深了我们对交叉不亲和性复杂调控的理解。
