Mediates trans-Golgi-network trafficking and cell elongation (PubMed:21512130, PubMed:23832588). Required for keeping the appropriate balance between secretory trafficking and vacuolar targeting of a subset of proteins (PubMed:21512130). The ECH/YIP4 complex is involved in the modulation of the trans-Golgi network (TGN)-mediated trafficking of some proteins and cell wall components (e.g. pectin and hemicellulose) to the cell wall in dark-grown hypocotyls and in secretory cells of the seed coat (PubMed:23832588). Component of a trans-Golgi network (TGN)-localized ECH/YIP4 complex made of ECH, YIP4A and YIP4B (PubMed:23832588). Interacts directly with YIP4A and YIP4B (PubMed:23832588). Severe size reduction of all organs (PubMed:21512130, PubMed:23832588). Abnormal cell wall composition (PubMed:23832588). Belongs to the TVP23 family.