basic helix-loop-helix (bHLH) domain found in Arabidopsis thaliana protein NAI1 and similar proteins
NAI1, also termed AtbHLH20, or EN 27, is a bHLH transcription activator that regulates the expression of at least NAI2, PYK10 and PBP1. It is required for and mediates the formation of endoplasmic reticulum bodies (ER bodies). It plays a role in the symbiotic interactions with the endophytes of the Sebacinaceae fungus family, such as Piriformospora indica and Sebacina.