Sheepgrass (Leymus Chinensis(Trin.) Tzvel.) is an economically and ecologically important forage in the grass family. Self-incompatibility (SI) limits its seed production due to the low seed-setting rate after self-pollination. However, investigations into the molecular mechanisms of sheep grass are lacking. Therefore, microscopic observation of pollen germination and pollen tube growth, as well as transcriptomic analyses of pistils after self- and cross-pollination, were performed. The results indicated that pollen tube growth was rapidly inhibited from 10 to 30 min after self-pollination and subsequently stopped but preceded normally after cross-pollination. Time course comparative transcriptomics revealed different transcriptome dynamics between self-and cross-pollination. A pool of SI-related signaling genes and pathways was generated, including genes related to calcium (Ca2+)signaling, protein phosphorylation, plant hormone, reactive oxygen species (ROS), nitric oxide(NO), cytoskeleton, and programmed cell death (PCD). A putative SI response molecular modeling sheep grass was presented. The model shows that SI may trigger a comprehensive calcium-and phytohormone-dominated signaling cascade and activate PCD, which may explain the rapid inhibition of self-pollen tube growth as observed by cytological analyses. These results provided new insights into the molecular mechanisms of sheep grass (grass family) SI
