Component of the IFT complex A (IFT-A), a complex required for retrograde ciliary transport (PubMed:27515926, PubMed:28479320). In particular, may act redundantly with the intraflagellar transport protein ift-43 to regulate the transport of specific ciliary cargo proteins such as che-3 which are related to motility (PubMed:28479320). Functions in cilia biogenesis (PubMed:27515926). Component of the IFT complex A (IFT-A) composed of at least che-11, daf-10, dyf-2, ift-139, ift-43 and ifta-1. Expressed in ciliated sensory neurons in the head and tail. Shorter cilia with an irregular morphology resulting in functional defects characterized by defective movement, dauer formation, and mating behavior (PubMed:27515926). Double knockout with intraflagellar transport protein ift-43 results in defective cilium morphology and function (PubMed:28479320). Belongs to the TTC21 family.