Functions redundantly with TRAF1B in the regulation of plant immune response. Contributes to the turnover of the nucleotide-binding domain and leucine-rich repeat-containing (NB-LRR) immune receptors SNC1 and RPS2. May associate with an E3 ubiquitin-protein ligase complex, which modulates ubiquitination and subsequent degradation of NB-LRR immune sensors to maintain their homeostasis (PubMed:26867179). Functions redundantly with TRAF1B in the regulation of autophagosome formation. Required for SINAT1- and SINAT2-mediated ubiquitination and destabilization of ATG6. Functions as molecular adapter that helps to regulate autophagy by modulating ATG6 stability (PubMed:28351989). Interacts with AHK3 (PubMed:18642946). Interacts with ATG6, SINAT1, SINAT2, SINAT5 and SINAT6 (PubMed:28351989). Predominantly expressed in the cytoplasm. Associates with starvation-induced autophagosomes in continuous darkness. No visible phenotype under normal growth conditions, but the double mutant plants traf1a and traf1b, or muse13 and muse14 are extremely dwarf when grown at room temperature.