Tissue-specific expression of AUX1 in maize roots

The cDNA of a maize homologue of Arabidopsis AUX1 was isolated. The deduced amino acid sequence of ZmAUX1 showed 73% identity to the corresponding AtAUX1 and displayed 7 to 10 putative trans-membrane domains. Northern experiments revealed ZmAUX1 expression in the tips of all maize root types, including the primary-, lateral-, lateral seminal- and crown-roots. In situ hybridisation experiments with tissue sections of the primary root showed that ZmAUX1 expression was highly tissue-specific, confined to the endodermal and pericycle cell layers of the primary root along the border of the central cylinder, as well as to the epidermal cell layer. This expression pattern makes ZmAUX1 useful as a new marker for studies of root development in maize.