Involved in cell specification during anther and pollen development. Required for the differentiation, specialization and persistence of tapetal cells in the anthers (PubMed:14615601, PubMed:16055681). May serve as an extracellular ligand for the EMS1 receptor kinase to signal cell fate determination during plant sexual reproduction (PubMed:18250314). Interacts with EMS1. Expressed in leaves, young seedlings, inflorescence meristems, floral meristems, carpel primordia and ovule primordia. Expressed in flower buds at development stage 2 in archesporial cells, in primary sporogenous cells and primary parietal cells at stage 3, and in secondary parietal cells at early stage 4. In microsporocytes, expression increases at stage 5 and at late stage 5, expressed predominantly in both tapetum and microsporocytes. Expression in tapetum and microsporocytes is reduced greatly at stage 6 and then declined gradually to be not detectable at stage 10. Male-sterile phenotype due to the absence of tapetum. Presence of extra microsporocytes in the developing anthers (PubMed:14615601). No effect on cell wall degradation during microsporocyte formation (PubMed:23893118).