Probable component of the calreticulin 3 (CRT3) complex, acting probably as a co-chaperone involved in protein retention in the endoplasmic reticulum lumen. Required for micropylar pollen tube guidance. Plays an essential role in cell plate orientation or positioning in early embryo patterning. Interacts with CRT3, but not with CRT1 or CNX. Exclusive ER lumen localization and no membrane localization in PubMed:21954464. Expressed in inflorescences, siliques, roots and shoots. Expressed in early embryo, endosperm, mature pollen and pollen tubes, synergide cells and weakly in antipodal cells. Defective in micropylar pollen tube guidance leading to zygotic lethality. Belongs to the TAPT1 family.