Gametophyte development in angiosperms occurs within diploid sporophytic structures and requires coordinated development; e.g., development of the male gametophyte pollen depends on the surrounding sporophytic tissue, the tapetum. The mechanisms underlying this interaction remain poorly characterized. The peptide CLAVATA3/EMBRYO SURROUNDING REGION-RELATED 19 (CLE19) plays a “braking” role in preventing the harmful overexpression of tapetum transcriptional regulators to ensure normal pollen development in Arabidopsis. However, the CLE19 receptor is unknown. Here, we show that CLE19 interacts directly with the PXY-LIKE1 (PXL1) ectodomain and induces PXL1 phosphorylation. PXL1 is also required for the function of CLE19 in maintaining the tapetal transcriptional regulation of pollen exine genes. Additionally, CLE19 induces the interactions of PXL1 with SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE (SERK) coreceptors required for pollen development. We propose that PXL1 and SERKs act as receptor and coreceptor, respectively, of the extracellular CLE19 signal, thereby regulating tapetum gene expression and pollen development.

被子植物的配子体发育发生在二倍体孢子体结构内，需要协调发育；例如，雄配子体花粉的发育取决于周围的孢子体组织，即绒毡层。这种相互作用背后的机制仍然知之甚少。肽CLAVATA3/EMBRYO SURROUNDING REGION-RELATED 19 (CLE19)在防止绒毡层转录调节因子的有害过度表达以确保拟南芥花粉正常发育方面发挥着“制动”作用。然而，CLE19 受体尚不清楚。在这里，我们证明 CLE19 直接与 PXY-LIKE1 (PXL1) 胞外域相互作用并诱导 PXL1 磷酸化。CLE19 维持花粉外壁基因转录调控的功能也需要 PXL1。此外，CLE19 诱导 PXL1 与花粉发育所需的体细胞胚胎发生受体样激酶 (SERK) 辅助受体相互作用。我们提出 PXL1 和 SERK 分别作为细胞外 CLE19 信号的受体和辅助受体，从而调节绒毡层基因表达和花粉发育。