Putative anti-apoptotic factor involved in the regulation of tapetal programmed cell death (PCD) and degeneration during anther development. Interacts directly with the DEAD-box ATP-dependent RNA helicases AIP1 and AIP2 that form dimers and bind the promoter region of the cysteine protease CP1 involved in tapetum PCD. Interacts with AIP1 and AIP2. During anther development, expressed in tapetal cells, parietal anther wall layers and microsporocytes from late stages 8 to stage 10. Male sterility due to lack of tapetal programmed cell death (PCD) and degeneration, leading to defects in formation of male gametophytes. Belongs to the API5 family.