Ethylene receptors are active without ethylene due to binding with other enzymatically active co-receptors such as constitutive triple response 1 (CTR1) and ethylene insensitive 2 (EIN2). Ethylene binding causes EIN2 to split in two, of which the C-terminal portion of the protein can activate different transcription factors to bring about the effects of ethylene. There is also non-canonical pathway in which ethylene activates cytokinin receptor, and thereby regulate seed development (stomatal aperture) and growth of root (the apical meristem).[1]