Probable aspartic protease activated by the transcription factor MYB80. May participate in the regulation of the timing of tapetal programmed cell death (PCD) which is critical for pollen development. During anther development, expressed from stage 6 to stage 9 in tapetal cells and developing microspores. Premature apoptosis-like programmed cell death (PCD) in tapetum and pollen from developing anthers, leading to collapsed pollen grains. Plants silencing UND exhibit partial male sterility with reduced silique elongation and seed set. Premature apoptosis-like programmed cell death (PCD) in tapetum from developing anthers, leading to collapsed pollen grains. Belongs to the peptidase A1 family.