Cysteine protease that may play a role in pollen development (PubMed:15356393). May be regulated by the transcription factor UDT1 in developing anthers and play a role in tapetum development (PubMed:16141453). Positively regulated by the transcription factor TDR in developing anthers and may play a role in tapetum programmed cell death (PCD) (PubMed:17138695). Highly expressed in the tapetum and developing pollen of the anther locules. Weakly expressed in root and germinating seed, hardly in the anther-less-flower and not detected in leaf. Plants show overall delay of growth and development, and mature plants are dwarf. Panicle of CP1 mutant contains several flowers which remain unfertilized due to the abnormal development of the pollen. Belongs to the peptidase C1 family.