Accessory subunit of the mitochondrial membrane respiratory chain NADH dehydrogenase (Complex I), that is believed to be not involved in catalysis. Complex I functions in the transfer of electrons from NADH to the respiratory chain. The immediate electron acceptor for the enzyme is believed to be ubiquinone (By similarity). Is required for correct plant growth and development. Complex I is composed of at least 49 different subunits. Expressed in roots, stems, flowers, rosette leaves, cauline leaves and siliques, with the highest expression in the stems. Shorter roots, smaller plants and delayed flowering. Belongs to the complex I LYR family.