Plays multiple roles in growth and development. Involved in nonsense-mediated mRNA decay (NMD). May provide a link to the mRNA degradation machinery to initiate NMD and serve as an adapter for UPF proteins function. Required for meiotic progression through anaphase II of pollen mother cells. May counteract cyclin-dependent kinase (CDK) activity at the end of meiosis. May play a role in plant defense through its involvement in NMD. Together with EXA1, helps to restrict cell death induction during pathogen infection in a salicylic acid- (SA) and reactive oxygen species- (ROS) independent manner (PubMed:29073135). Interacts with EXA1. Expressed in flowers and at lower levels in stems and leaves. Embryonic lethality when homozygous (PubMed:18544632). No spontaneous lesions, but enhanced cell death independent of salicylic acid (SA) biosynthesis or reactive oxygen species (ROS) production during pathogen infection (PubMed:29073135).