CrRLK1L receptor-like kinases HERK1 and ANJEA are female determinants of pollen tube reception

Communication between the gametophytes is vital for angiosperm fertilisation. Multiple CrRLK1L-type receptor kinases prevent premature pollen tube burst, while another CrRLK1L protein, FERONIA (FER), is required for pollen tube reception in the female gametophyte. We report here the identification of two additional CrRLK1L homologues, HERCULES RECEPTOR KINASE 1 (HERK1) and ANJEA (ANJ), which act redundantly to promote pollen tube growth arrest at the synergid cells. HERK1 and ANJ localise to the filiform apparatus of the synergid cells in unfertilised ovules, and in herk1 anj mutants a majority of ovules remain unfertilised due to pollen tube overgrowth, together indicating that HERK1 and ANJ act as female determinants for fertilisation. As in fer mutants, the synergid cell-specific, endomembrane protein NORTIA (NTA) is not relocalised after pollen tube reception; however, unlike fer mutants, reactive oxygen species levels are unaffected in herk1 anj double mutants. Both ANJ and HERK1 associate with FER and its proposed co-receptor LORELEI (LRE) in planta. Together, our data indicate that HERK1 and ANJ act with FER to mediate female-male gametophyte interactions during plant fertilisation.

被子植物受精过程中，配子体间的通讯至关重要。多种CrRLK1L类受体激酶可防止花粉管过早爆裂，而雌配子体中的另一CrRLK1L蛋白FERONIA（FER）是花粉管接收所必需的。本研究鉴定到两个新的CrRLK1L同源基因：HERCULES RECEPTOR KINASE 1（HERK1）与ANJEA（ANJ），二者功能冗余，可促进助细胞处的花粉管生长停滞。未受精胚珠的助细胞丝状器中可检测到HERK1与ANJ的定位；在herk1 anj双突变体中，多数胚珠因花粉管过度生长而无法完成受精，这表明HERK1与ANJ可作为受精过程中的雌性决定因子。与fer突变体类似，助细胞特异性内膜蛋白NORTIA（NTA）在花粉管接收后未发生重新定位；但与fer突变体不同的是，herk1 anj双突变体的活性氧水平并未受到影响。在植物体内，ANJ与HERK1均可与FER及其潜在共受体LORELEI（LRE）发生互作。综上，本研究数据表明，HERK1与ANJ可与FER协同作用，介导植物受精过程中的雌雄配子体互作。