Arabidopsis thaliana Raw sequence reads. Arabidopsis thaliana

Plants have evolved to employ leucine-rich repeat receptor-like kinases (LRR-RLKs), the largest family of RLKs, to control growth, development, and defense. In Arabidopsis, the EMS1 (EXCESS MICROSPOROCYTES 1) LRR-RLK and its small protein ligand TPD1 (TAPETUM DETERMINANT 1) are required for somatic and reproductive cell specification during early anther development; however, the molecular mechanism by which TPD1/EMS1 signaling controls cell differentiation remains elusive. Here, we report that the epidermis-specific expression of TPD1 promotes cell proliferation in wild-type and tpd1 anthers and ovules. Ectopic co-expression of EMS1 and TPD1 affects cell proliferation, expansion, and elongation in stem. Moreover, RNAseq analysis shows that TPD1/EMS1 signaling alters expression of core cell cycle genes and auxin signaling genes. In addition, we found that expression of CYCD3;3 and CYCA2;3 is increased in AtML1:TPD1 ovules and anthers. Manipulating the TPD1 expression also causes the ectopic expression of DR5:GFP in ovules and anthers. Thus, our results suggest that the TPD1/EMS1 signal transduction pathway activates cell proliferation through regulating auxin signaling.